yellow jacket 3788 Series User manual

Operation Manual
37837 / 37880 / 37881 / 37882 / 37887 / 37888 / 37889
3788X Series (includes 37837)
P/N 380539 RevF

2
Refrigerants: All Models: R-134a
Compressor: 2-1/2 HP Hermetic Compressors
Power Source: 120V AC 60Hz for US Models 230V AC 50Hz for CE Models
Amperage: RLA: 8.5 RLA:
FLA: 11.0 FLA:
LRA: 30.0 LRA: 19.0
Size: 37880
Height: 45 inches
Width: 19.5 inches
Depth: 29 inches
Weight: Maximum is deluxe unit at 225 lb. with tank
Before operating this unit, please read this
manual thoroughly. You must understand the
procedures outlined in this manual. Failure to
follow these procedures could void all war-
ranties.
Before handling refrigerants, read the material
safety data sheet (MSDS) from the refrigerant
manufacturer.
Inhalation of high concentration of refriger-
ant vapors is harmful and may cause heart
irregularities, unconsciousness, or death.
Deliberate inhalation of refrigerants is ex-
tremely dangerous. Death can occur without
warning. Vapors reduce oxygen available
for breathing and are heavier than air. De-
composition products are hazardous. Liquid
contact can cause frostbite. All refrigerant
containers, equipment, and hoses are under
pressure.
3788X Series Refrigerant Management System
Section Page Section Page
Specifications 2 OPTION 6: Tank Refill 10
Safety Instructions 3 OPTION 7: Refrigerant Management System 11
Component Diagram 4 Purging Non-Condensable Gases 12
Control Panel Overview 5 Maintenance Reminders 12
Setup/Check List/User Op-
tions
6 Filter change/compressor oil/vacuum oil 13
Option 1: Recovery Only 6 Troubleshooting Information 14
OPTION 2: Vacuum 7 Common Problems 14
OPTION 3: Charge Only 8 LCD Error Messages 15
OPTION 4: Full Cycle 9 Repair Parts List 16
OPTION 5: Oil Inject 10 Warranty Information 16
Table of Contents
Specifications

3
Know your equipment. Read and understand the oper-
ation manual and labels affixed to the unit. Learn it’s
application and limitations as well as the specific po-
tential hazards of your equipment.
ALWAYS WEAR SAFETY GOGGLES.
Ground all equipment. This unit is equipped with an
approved 3 prong grounding-type plug. The green
ground wire should never be connected to a live ter-
minal.
Use the Proper Extension Cords. Use the following
guide for choosing the proper extension cord:
Wire Maximum Length
18 Ga. - 10 feet 16 Ga. - 25 feet
14 Ga. - 50 feet 12 Ga. - 100 feet
Avoid Dangerous Environments. Do not use this unit
in damp locations or expose it to rain. This equipment
should be used in a location with mechanical ventila-
tion that provides at least four air changes per hour.
This equipment should not be used near open con-
tainers of flammable liquids.
Disconnect Unit from Power Supply Before Servicing.
An electrical shock hazard is present when the unit is
disassembled or the cowling is removed.
Repair Damaged Parts. Do not operate the unit with a
defective part. Repair unit to proper operating condi-
tions.
Use Recommended Accessories. Follow instructions
that accompany all accessories. Improper use of ac-
cessories may damage equipment or create a hazard.
Use Caution When Connecting or Disconnecting.
Improper usage may result in refrigerant burns
(frostbite). If a major refrigerant leak occurs, proceed
immediately to a well ventilated area. The hoses in-
cluded with this unit are supplied with couplers that,
when closed, prevent refrigerant vapors from venting
when disconnecting from the automobile.
Only Use the 37880 with the Correct Refrigerants.
The 37880 Series is only approved for R-134a
Operate the Unit within the Design Environment. The
37880 was designed to operate in a temperature range
from 40°F to 120°F. The unit should also not be
operated in a wet location.
WARNING! Refrigerant, in liquid and vapor form, is
a potentially hazardous material. Please consult the
manufacturer’s Material Safety Data Sheet for
additional information and adhere to the following
safety guidelines:
Avoid breathing high concentrations of vapors.
Use with sufficient ventilation to keep operator
exposure below recommended limits, especially in
enclosed and low lying areas.
Avoid contact of liquid refrigerant with the eyes
and prolonged skin exposure.
Wear goggles and protective gloves.
Do not attempt to operate this unit above 120°F
ambient temperature.
Do not allow refrigerants to contact open flame.
Refrigerant decomposition in a flame results in
phosgene gas. Breathing phosgene gas can be
fatal.
FIRST AID: If high concentrations of refrigerant are
inhaled, immediately remove the victim to fresh air.
Call a physician or emergency medical technician.
Keep calm. If not breathing, give artificial respiration.
If breathing is difficult, give oxygen. Do not give
epinephrine or similar drugs.
EYE: In case of liquid contact, immediately flush
eyes with plenty of water. Call a physician.
SKIN: Flush with water. Treat for frostbite, if
necessary, by gently warming the effected area.
CAUTION! All refrigerant hoses, recovery tanks,
refrigerant lines, the 37880, and other vessels
containing refrigerants should be handled as if under
high pressure.
CAUTION! Should be operated by certified personnel.
CAUTION! Avoid breathing A/C refrigerant and lubri-
cant vapor or mist. Exposure may irritate eyes, nose
and throat. To remove HFC-134a from the A/C system,
use service equipment certified to meet the require-
ments of SAE J2788. Additional health and safety
information may be obtained from refrigerant and
lubricant manufacturers.
CAUTION! Do not pressure test or leak test HFC-134a
service equipment and/or vehicle air conditioning
systems with compressed air. Some mixtures of air
and HFC-134a have been shown to be combustible at
elevated pressures. These mixtures, if ignited, may
cause injury or property damage. Additional health
and safety information may be obtained from refriger-
ant and lubricant manufacturers.
General Safety Instructions

4
Component Location and Description
1. Touch Pad (Control Panel)
2. High Gauge
3. Low Gauge
4. Auto High Side Hose (Red)
5. Auto Low Side Hose (Blue)
6. Tank Vapor Hose (Red)
7. Tank Liquid Hose (Blue)
8. Oil Drain Bottle
9. Oil Inject Bottle (excluded on 37837,
37887 and 37888)
10. Tool Tray
11. Main Power Switch
12. Storage Tank
13. Vacuum Pump
11.
4.
1.
2.
8.
5.
9.
3.
10.
7.
6.
13.
12.

5
LCD Display
The Liquid Crystal Display (LCD) display provides
the unit operator with continual updates of the
status. In addition, the display will prompt the
technician for the user input needed to continue
operation. The LCD shows error codes for rapid
diagnosis of abnormal conditions.
The display is divided into five fields which aid the
technician in rapidly reading information.
1. Weight - Shows the weight of refrigerant being
processed in each mode.
2. Time (MINS) - Shows the time set for Vacuum.
Timer will count down to display the time left.
3. Purge–Located in the bottom right corner of
display. A “Y” in this field indicates non-
condensable gases such as air are present in
the storage tank. The unit will purge automati-
cally next time the unit is turned on when the
“Y” is displayed. An “N” indicates non-
condensable gases are below the set limit. An
“E” indicates the unit purged for fifteen (15)
seconds and non-condensable gases are still
present. This is a safety feature which prevents
excess purging when a malfunction occurs
somewhere in the system. See the Purging Non
-Condensable Gas section for further details.
4. Option - Displays the Option number of the cur-
rent operation.
5. Status Line - Displays programming commands
and informs the user of current status of the
unit.
Available Functions:
The main menu allows you to access the following
functions.
1. Option 1 - Recover, is used to recover and
recycle refrigerant from an automobile A/C
system. This Option is most often used prior to
opening an A/C system to atmosphere to
replace a system component.
2. Option 2 - Vacuum, is used to vacuum air/
moisture from a system previously opened to
the atmosphere. This Option will then proceed
to recharge the A/C system. This Option also
allows the technician to verify the A/C system
will hold a vacuum for a certain length of time.
3. Option 3 - Charge Only, adds refrigerant to an
A/C system.
4. Option 4 - Full Cycle, performs a complete
recovery, recycling, evacuating and charging of
an automobile A/C system.
5. Option 5 - Oil injection, is used to inject oil into
the Automobile’s A/C system. (37887 and
37888) Hybrid Hose Flush, is used to clear the
hoses of oil before using the unit on a hybrid
A/C system. DOES NOT APPLY TO 37837.
6. Option 6 - Tank Refill, is used to add new
refrigerant to the storage tank.
7. Option 7–Vehicle Oil Flush, is used to flush the
oil from the vehicles A/C system.
8. Option 8 - Refrigerant Management System,
gives the technician access to information
about refrigerant use to date.
9. Option 9–Set-up, is used to access settings like
time and date, Scale calibration and system
information.
Function Keys / Numeric keypad
The Function Keys are used to enter data into the
system in a variety of modes.
UP ARROW–This key allows you to scroll up
through the menu
Down ARROW–This key allows you to scroll down
through the menu
Left ARROW - This key allows you scroll left
through the menu
Right ARROW - This key allows you to scroll right
through the menu
Numeric Key pad–these keys are used to select
desired time and weight and entering the filter
codes.
START- Press START to begin a selected opera-
tional mode.
ENTER–Press ENTER to enter the desired function
or setting
RESET- Press RESET to cancel the current opera-
tion. The RESET may have to be pushed more than
once to return to “Main Menu”
Control Panel Features

6
Initial Setup
To ensure quick, successful integration of the re-
covery machine into your shop, please follow these
set-up procedures before the first use of the unit.
Step 1: FILL VACUUM PUMP WITH OIL
1. Remove thumbscrews located under the vacu-
um pump shelf.
2. Rotate the front of the vacuum pump out to ex-
pose the oil fill port.
3. Remove the fill cap located on top of the vacu-
um pump.
4. Using a funnel, insert oil to the oil level line us-
ing the provided YELLOW JACKET®vacuum
pump oil.
5. Replace the oil fill cap.
6. Rotate the vacuum pump back into its original
position and replace the thumbscrews.
Step 2: FILL SOURCE TANK WITH REFRIGERANT
(also see page 11)
1. Disconnect blue tank hose from tank.
2. Open blue tank valve and allow nitrogen to vent.
3. Reconnect blue tank hose.
4. Attach the tank refill adapter (Part No. 19153) to
the R-134a virgin cylinder. WARNING: DO NOT
OVER-TIGHTEN THE TANK REFILL ADAPTER.
5. Plug unit into a grounded 110V outlet.
6. Turn on the main power switch.
7. Select TANK REFIL from the main menu
8. Follow the user prompts to complete the tank
refill process.
9. When the display reads “SUPPLY TANK EMP-
TY” disconnect blue hose.
10. Remove the tank refill adapter from empty R-
134a virgin cylinder and place it in the tool tray
located on top of the unit.
The unit is now ready for operation.
View Training Video:
https://yellowjacket.com/product/refrigerant-
management-system-3788x/
The Recovery Option should be used to fully recovery
and recycle all refrigerant from an air conditioning
system. For instance, if the system needs to be
opened to atmosphere to replace a part, all refrigerant
must be removed before opening the system.
RECOVER Operational Steps:
1. Verify the automobile air conditioning system
is off.
2. Select RECOVER for recovery operations. The
LCD should read “CONNECT SERVICE HOSES
TO VEHICLE ENTER TO CONTINUE.”
NOTE: If desired, the gauges of the 3788X SERIES
can now be used to aid investigation of an A/C system
problem. Ensure the automobile A/C system is turned
off prior to selecting a mode on the machine.
3. Connect the high and low side auto service
hoses to the respective high and low side ser-
vice ports on the automobile A/C system. Open
the service hose valves.
4. Press START to begin recovery operations.
WARNING: DO NOT RECOVER CONTAMINATED
REFRIGERANT WITH THIS UNIT. RECOVERING
CONTAMINATED REFRIGERANT WILL VOID ALL
WARRANTIES AND MAY CAUSE DAMAGE TO OTHER
AUTOMOBILES SERVICED IN THE FUTURE.
During the recovery operation, refrigerant is removed
from both the high and low side of the automobile air
conditioning system. The LCD will display the amount
of refrigerant being recovered and the status line will
read “RECOVERING REFRIGERANT.”
Note: If “RECOVERY HOLD” Option is selected The
unit will stop at 6” of mercury and hold for five min as
required by EPA Per SAE J2211. If the pressure rises
to 0 psi the compressor will restart and the unit will
pull down to the required 6” of mercury and hold for
two minutes. The unit will repeat this process until the
system pressure remains stable at vacuum for two
minutes or until it fails this process five times. If the
process fails five times the status line will read “LEAK
CHECK FAILED.” This may mean that the automobile
A/C system has a gross leak and it will not hold a vac-
uum.
If this occurs take the appropriate steps to locate the
leak and properly repair it.
If the “RECOVERY HOLD” option is not selected the
unit will shut off at the required level of vacuum and
the operator must insure that the EPA standard (SAE
J2211) is met.
After the system turns off, the unit will beep to alert
the technician the job is complete. The oil removed
from the auto will drain into the oil drain bottle on the
side of the unit. Because a small amount of gas will be
released as the oil drains, a small hissing sound may
come from the bottle.
Always inspect hoses, o-rings, and fittings for dam-
age before using equipment. Replace worn or dam-
aged components. Failure to insure that hoses, o-
rings and fittings are in working order can increase a
build-up of NCG’s in the recovered refrigerant.
RECOVER

7
Use only new lubricant to replace the amount
removed during the recycling process. Discard
used lubricant per applicable federal, state and
local requirements.
5. Verify the message on the LCD reads
“RECOVERY COMPLETE.”
6. Press the RESET key. The LCD should read
“CHECK OIL LEVELS.”
7. Measure the oil in the oil drain bottle. Dispose of
recovered oil in a proper manner.
8. Close the service valves and disconnect the
high and low side auto service hoses from the
automobile.
Models with the optional refrigerant identifier
37881/37888
The unit will display “IDENTIFY REFRIGERANT?”
To make your selection use the left or right arrow
keys to toggle from YES to NO. Press the ENTER
key to make your selection and then press the Start
key to start the process. If YES is selected the unit
will begin the refrigerant identification process.
If the refrigerant does not pass the identification
process (98% purity) the unit will display the error
message “ CONTAMINATED” and the screen will
show the results of the identification. Press the
Reset key and follow the instructions on the screen
and the unit will clear itself automatically. Repeat
the identification process to insure the proper
identification of the refrigerant purity level.
If the unit fails the second time follow the on screen
instructions and take the appropriate steps to re-
move the contaminated refrigerant with a separate
unit for removal of contaminated refrigerant.
WARNING: DO NOT RECOVER CONTAMINATED
REFRIGERANT WITH THIS UNIT. RECOVERING
CONTAMINATED REFRIGERANT WILL VOID ALL
WARRANTIES AND MY CAUSE DAMAGE TO OTH-
ER AUTOMOBILES THAT YOU SERVICE IN THE FU-
TURE.
RECOVER, cont.
VACUUM
The vacuum function of the 37880 SERIES is de-
signed to remove air/moisture from the automobile
A/C system by pulling a deep vacuum. This mode
is most often used after completing a repair that
required opening the A/C system to the atmos-
phere. Moisture in an A/C system can cause erratic
operation and must be removed before recharging
the system with refrigerant.
VACUUM Operational Steps
NOTE: If desired, the gauges of the 880 SERIES
can now be used to aid investigation of an A/C sys-
tem problem. Ensure the automobile A/C system is
turned off prior to selecting a mode on the ma-
chine.
1. Verify the auto air conditioning system is off.
2. Select Vacuum option from the main menu.
3. Press the ENTER key.
4. When the LCD reads “SET VACUUM TIME,” set
the vacuum time by using the numeric keypad
until the desired time is shown. press ENTER to
accept the vacuum time shown on the LCD.
Bypass vacuum time by setting time to zero
(FULL CYCLE MODE only). Note: We recom-
mend 10-15 minimum vacuum time to ensure
proper charging.
5. When the LCD reads “SET VACUUM HOLD
TIME,” set the vacuum hold time by using the
numeric keypad until the desired time is shown.
press ENTER to accept the vacuum hold time
shown on the LCD. Vacuum hold time can be
bypassed if the time is set to zero.
6. The display will now read “INJECT OIL AFTER
VACUUM” YES or NO Press the left or right
arrows to select YES or NO.
7. The LCD will read “CONNECT HOSES PRESS
ENTER TO CONTINUE”
8. Connect the high and low side auto service
hoses to the respective high and low side ser-
vice ports on the automobile A/C system. Open
the service hose valves.
9. Press START key to begin vacuum operation.

8
VACUUM cont.
Note: If the automobile A/C system has pressure on
it, the unit will automatically begin a recovery cycle
to insure that no refrigerant is released into the
atmosphere.
10. The 3788X SERIES will begin to evacuate the A/
C system and will beep to indicate the end of
the vacuum time.
11. Record vacuum level shown on the LCD and
press START to begin the vacuum hold time.
The hold time will count down on the LCD and
the unit will beep at the end of the hold time.
12. Record the final vacuum level shown on the
LCD If the two recorded vacuum levels are dif-
ferent, the A/C system may have a leak and
might not retain refrigerant when charged.
13. The unit will prompt you to “INJECT OIL NOW”
press and hold the START key until the desired
amount of oil is injected into the A/C system.
14. Verify the message on the LCD reads “VACUUM
COMPLETE.”
15. Press the RESET key to return to main menu.
16. Shut the service valves and disconnect the
high and low side auto service hoses from the
automobile.
Model 37889 with integrated micron gauge (Only) -
See page 9 for instructions that will outline how to
use this feature.
CHARGE
The Charge Only function is designed to add a
precise amount of refrigerant when the A/C system
is low on refrigerant. This mode is most often used
when the A/C system is working but does not
produce sufficiently cold air. Note: THE A/C
SYSTEM MUST BE IN A VACUUM BEFORE THE
CHARGING PROCESS.
MODE 3 Operational Steps:
NOTE: If desired, the gauges of the 3788X can now
be used to aid investigation of an A/C system
problem. Ensure the automobile A/C system is
turned off prior to selecting a mode on the 3788X.
1. Verify the auto air conditioning system is off.
2. Select CHARGE option from the main menu.
3. When the LCD reads “SET CHARGE AMOUNT,”
set the amount of refrigerant to be charged into
the A/C system by using the numeric keypad
until the desired amount is shown. press ENTER
to set the charge amount on the LCD. NOTE:
To change units from pounds and ounces,
ounces or kilograms press the START key. The
unit will then ask you to confirm the charge
amount. Press the ENTER key to confirm.
4. The LCD will read “CONNECT SERVICE HOSES
TO THE VEHICLE ENTER TO CONTINUE”. Press
the ENTER key.
5. Connect the high and low side auto service
hoses to the respective high and low side
service ports on the automobile A/C system.
Open the service hose valves.
6. The LCD should read “PUSH START.”
7. Press START key to begin charging operations.
The display will read “STABILIZING PLEASE
WAIT” The 3788X Series will then start the
charge cycle.
The LCD will display the charging process
progress. The unit will beep when desired charge
amount has been transferred to the A/C system.
NOTE: The last 3 oz. of refrigerant charge will be
metered in by the charging solenoid. It is normal to
hear a clicking sound while charging.
8. Verify the message on the LCD reads “CHARGE
COMPLETE.” Press the RESET key and the Unit
will force a hose clearing routine. Close the
service valves and disconnect the high and low
side auto service hoses from the auto.
9. Press ENTER key to return to the main menu.
Low Side Charge:
The system default setting is high-side charging.
To charge low-side, follow these steps:
1. Turn the unit off.
2. Press and hold number 3 key down on the
numeric key keypad and turn the unit on.
3. When the display reads “low side charge,”
release the charge key.
4. Enter the charge amount.
NOTE: when the unit is turned off it will default
back to high-side charge.

9
The Full Cycle function of the 3788X is designed to
remove and recycle all refrigerant in an A/C system
by transferring the refrigerant to the storage tank,
remove moisture in the system by pulling a
vacuum, and charging the system with a precise
amount of refrigerant.
MODE 4 Operational Steps:
NOTE: If desired, the gauges of 3788X can now be
used to aid investigation of an A/C system problem.
Ensure the automobile A/C system is turned off
prior to selecting a mode on the 3788X.
1. Verify the auto air conditioning system is off.
2. Select Full Cycle in the main menu. The LCD
will read “SELECT VACUUM TIME”.
3. When the LCD reads “SET VACUUM TIME,” set
the vacuum time by entering the time using the
numeric keypad until the desired time is shown.
Press the ENTER key to continue.
4. When the LCD reads “SET VAC HOLD TIME,”
set the vacuum hold time by entering the time
using the numeric keypad until the desired time
is shown. Press the ENTER key to continue.
Note: We recommend 10-15 minimum vacuum time
to ensure proper charging.
NOTE: Vacuum hold time can be bypassed if the
time is set to zero.
1. When the LCD reads “SET CHARGE AMOUNT,”
set the charge amount by entering the amount
using the numeric keypad until the desired time
is shown. Press the ENTER key to continue.
6. When the LCD reads “INJECT OIL AFTER
VACUUM”, use the left and right arrow keys to
toggle between YES and NO. Select YES or NO
and press the ENTER key to continue.
7. The LCD should read ‘CONNECT SERVICE
HOSES TO VEHICLE’,
8. Press START KEY to begin full cycle operations.
9. The unit will begin to recover as outlined for the
Recovery Only cycle, and then evacuate the A/C
system and will beep to indicate the end of the
vacuum time—if Vacuum Hold is used.
10. Record the vacuum level shown on the low
pressure gauge and press START to begin the
vacuum hold time. The hold time will count
down on the LCD and the unit will beep at the
end of the hold time. If vacuum hold time was
set to zero, the unit will transition into charge
mode.
11. Record the final vacuum level shown on the low
pressure gauge. If the two recorded levels are
different, the A/C system may have a leak and
may not retain refrigerant when charged. The
37880 will automatically start the charge cycle.
12. The unit will prompt you to “INJECT OIL NOW”
press and hold the START key until the desired
amount of oil is injected into the A/C system.
13. The LCD will display the progress of charging
process. When desired charge amount has been
transferred to the A/C system, the unit will beep.
14. Verify the message on the LCD reads “FULL
CYCLE COMPLETE.”
15. Press the RESET key. The LCD should read
“CHECK OIL LEVELS.” The LCD will read
“HOSES NEED CLEARING”
16. Press the Enter Key. The unit will then prompt
you to “DISCONNECT VEHICLE.”
17. Shut the service valves and disconnect the
high and low side auto service hoses from the
automobile.
18. Press the ENTER key; the LCD will read
“CLEARING HOSES.”
19. Measure the oil in the oil drain bottle. Dispose
of recovered oil in a proper manner.
20. Press the RESET key to return to the “SELECT
MODE” status.
INTERGRATED MICRON GUAGE (37889 MODEL
ONLY) The 37889 model has an integrated micron
gauge that can be used to determine the micron
level of the A/C system. The instructions below will
outline how to use this feature .
Full Cycle / Vacuum Operations –Select micron
level by using the up or down arrows. If you would
rather enter a time for the vacuum cycle press the
START key. Use the numeric keypad to set vacuum
time. NOTE: Because of the location of the vacuum
sensor it may be necessary to set the micron lever
lower to compensate.
NOTE: Since the micron sensor is inside the unit
and not attached to the vehicle, there will be a dif-
ference in the actual micron reading in the vehicle.
To achieve the best results set the micron number
lower than the micron level you want to reach.
FULL CYCLE

10
Models with the optional refrigerant identifier
37881/37888.
The unit will display “IDENTIFY REFRIGERANT?”
To make your selection use the left or right arrow
keys to toggle from YES to NO. Press the ENTER
key to make your selection and then press the
START key to start the process. If YES is selected
the unit will begin refrigerant identification process.
If the refrigerant does not pass the identification
process (98% purity) the unit will display the error
message “CONTAMINATED” and the screen will
show the results of the identification. Press the
RESET key and follow the instructions on the
screen and the unit will clear itself automatically.
Repeat the identification process to insure the
proper identification of the refrigerant purity level.
If the unit fails the second time follow the on screen
instructions and take the appropriate steps to re-
move the contaminated refrigerant with a separate
unit for removal of contaminated refrigerant.
WARNING: DO NOT RECOVER CONTAMINATED
REFRIGERANT WITH THIS UNIT. RECOVERING
CONTAMINATED REFRIGERANT WILL VOID ALL
WARRANTIES AND MY CAUSE DAMAGE TO
OTHER AUTOMOBILES THAT YOU SERVICE IN
THE FUTURE.
FULL CYCLE cont.
HYBRID HOSE FLUSH
The Hybrid Hose Flush feature is used to remove
residual oil and contaminates from the unit and
hoses. The SAE J2788 H standard requires that the
unit remove the residual oil so there isn't a risk of
cross contaminating the oil in a hybrid A/C system.
Failure to perform this function before working
on a hybrid A/C system can cause serious issues
with the electrical system. Having too much of the
wrong type of oil in a hybrid A/C system can
conduct the electricity to the outside of the A/C
compressor.
SERVICING HIGH VOLTAGE A/C SYSTEMS
(MODELS 37837, 37887 AND 37888 ONLY)
Due to issues with oil contamination in High Volt-
age A/C systems the 37837, 37887 and the 37888
have a unique flushing feature that reduces cross
contamination of oil below SAE and OEM specifica-
tions.
It is necessary to perform the following procedure
before working on a High Voltage A/C system.
1. Select HYBRID HOSE FLUSH in the main menu
2. When the display reads “PLEASE CONNECT
FLUSH ADAPTER” connect the supplied flush
adapter between the high and low side hoses.
3. Press the ENTER key to begin the process
4. The display will then read “FLUSHING HOSES
PLEASE WAIT”
5. When the process is complete press the RESET
key to return to the main menu.
WARNING:
FAILURE TO PERFORM THIS PROCESS CAN
CAUSE DAMAGE TO THE A/C SYSTEM
COMPRESSOR AS WELL AS OTHER ELECTRICAL
COMPONENTS RELATED TO THE A/C SYSTEM.
THE POSIBILITY OF ELECTRICAL SHOCK TO THE
TECHNICIAN OR OTHERS MAY ALSO OCCUR BY
NOT PERFORMING THIS PROCESS.
INTERGRATED MICRON GUAGE
(37889 MODEL ONLY)
The 37889 model has an integrated micron gauge
that can be used to determine the micron level of
the A/C system.
Instructions on how to use this feature:
Full Cycle / Vacuum Operations –Select micron
level by using the up or down arrows. If you would
rather enter a time for the vacuum cycle press the
START key. Use the numeric keypad to set
vacuum time. NOTE: Because of the location of
the vacuum sensor it may be necessary to set the
micron lever lower to compensate.

11
TANK REFILL
In order to use the charging mode, you must have
at least ten (10) pounds of refrigerant in the storage
tank. Follow this procedure to add refrigerant to the
storage tank. When adding R-134a to the onboard
storage tank you will need to use the tank refill
adapter (PART NUMBER 19153) supplied in the
accessory kit. This adapter connects the low side
auto service coupler to the tank of new R-134a
refrigerant. It should be stored in the tool tray on
the top of the unit.
1. Select TANK REFIL from the main menu.
2. Connect the blue low side auto service hose to
the new refrigerant source tank and open the
tank valve. Turn the source tank upside down to
ensure all of the refrigerant is transferred to the
storage tank on the unit. Press the ENTER key.
3. Make sure you are reading pressure on the low-
side gauge.
4. Press the START key. Refrigerant will transfer to
the storage tank. The unit will shut off automati-
cally when either the supply tank is empty or the
storage tank is full.
Press the RESET key to return to the main menu.
Models with the optional refrigerant identifier
37881/37888:
The unit will display “IDENTIFY REFRIGERANT ?”
To make your selection use left or right arrow keys
to toggle from YES to NO. Press the ENTER key to
make your selection and then press the START key
to start the process. If yes is selected the unit will
begin the refrigerant identification process.
If the refrigerant does not pass the identification
process (98% purity) the unit will display the error
message “ CONTAMINATED” and the screen will
show the results of the identification. Press the
Reset key and follow the instructions on the screen
and the unit will clear itself automatically. Repeat
the identification process to insure the proper
identification of the refrigerant purity level.
If the unit fails the second time follow on screen
instructions and take appropriate steps to remove
the contaminated refrigerant with a separate unit
for removal of contaminated refrigerant.
REFRIGERATION MANAGEMENT
The Refrigerant Management System built into the
3788X tracks all aspects of refrigeration usage. The
information can significantly help you manage your
automobile A/C repair business. In addition, new
federal regulations require strict records of your
refrigerant usage. The software in this system is
designed to ensure the highest possible accuracy
in managing refrigerant usage. Refrigerant meas-
urement during charging is extremely accurate. In
Charge mode, however, accuracy is plus or minus
1/2 ounce based on variations in air temperature
and pressure.
Uses of the refrigerant data include:
Improved record keeping
Accurate determination of net profits
Reduced billing errors
Minimized refrigerant loss from leaks and theft
Reduced operator errors
The refrigerant management information is stored
in eight registers. To access the information, press
Mode 7, REFRIGERANT MANAGEMENT SYSTEM.
Press RMM key to cycle through the screens.
The screens contain the following information:
Screen 1: Last Job Information
Run Time
Refrigerant Recovered
Refrigerant Charged
Refrigerant Added
Screen 2: Year-to-date Information
Total Run Time
Total Amount Recovered
Total Amount Charged
Refrigerant Added “New”
WARNING
DO NOT RECOVER CONTAMINATED REFRIGERANT WITH THIS UNIT. RECOVERING CONTAM-
INATED REFRIGERANT WILL VOID ALL WARRANTIES AND MAY CAUSE DAMAGE TO OTHER
AUTOMOBILES THAT YOU SERVICE IN THE FUTURE.

12
Purging Non-Condensable Gases
The 3788X is designed to automatically purge non-
condesable gases such as air present in the
storage tank. When the pressure in the tank
exceeds a treshold value, the unit will automatically
purge the excess pressure. The unit will only purge
when it is first turned on. The current purge status
is displayed in the bottom right corner of the LCD
when in Select Mode.
The purge status should be either “Y”, “N”, or “E.”
A “Y” indicates air is present in the tank. The unit
will purge the next time it is turned off and on. An
“N” in the window indicates a purge is not needed.
An “E” will display on the LCD if the previous purge
was insufficient to lower the non-condensable gas
value below the limit. The purge time is set to 15
seconds to minimize refrigerant loss. If the LCD
continues to display an “E” after several purge
cycles, there may be an error in the system. Check
the pressure in the tank to determine if the system
is purging unnecessarily.
The best time to check the purge function is after
the unit has sat overnight and the tank temperature
is stable.
Maintenance Reminders
FILTER - MAINTENACE WARNING!
CHANGE FILTER DRIER
The 3788X has a unique filter system which
ensures the refrigerant transferred to the storage
cylinder is clean and moisture-free. The filters must
be changed periodically to ensure the system is
working properly. A maintenance reminder prompts
you when to change your filters. All refrigerant
must be removed from the old filters before they
are removed. Follow the filter change procedures
carefully to minimize refrigerant loss and ensure
only clean, moisture-free refrigerant is transferred
into the storage cylinder.
The new J2788 standard requires that the unit lock
out if the filter drier is not replaced at the proper
interval. The unit will prompt you when it is near the
end of its life. When the filter drier reaches 100 lbs
of refrigerant processed it will warn the user that it
is nearing the end of its life. When the filter drier
reaches 150 lbs of refrigerant processed it will lock
the user out and require a filter change before the
unit can be used again. The filter driers are marked
with a unique code that will be required to unlock
the unit.
Check Filter Life
Select the REF MANAGEMENT option in the
main menu.
Press the RIGHT ARROW key to view the
remaining filter life.
Filter Change Procedure before Scheduled Fil-
ter Change.
Follow these steps to change the filter drier before
the scheduled filter change:
Hold down DOWN ARROW key and turn main
power switch on.
When display reads “INPUT SERIAL NUMBER”
enter serial number using the keypad.
Filter Change Procedure if Filter Lock Out is
Reached.
When the display reads “ MAINTENACE
WARNING! CHANGE FILTER DRIER”
Press Enter key to enter filter change mode.
Enter serial number using the keypad

13
Maintenance—Compressor Oil
The oil should be checked for contamination and
proper oil level when the compressor oil mainte-
nance reminder is displayed. Select RESET to turn
reminder off until the next time you start the unit.
Select ENTER to reset the reminder until the next
scheduled maintenance.
Instructions for Oil Maintenance
Oil Level Check
1. Place unit on a level surface and run a recovery
cycle with the unit.
2. Unplug unit.
3. Remove front cover of unit.
4. SLOWLY remove oil port cap on compressor.
Note: High pressure may be present, remove cap
slowly.
5. Place rear wheels of unit on a 2 x 4.
6. Oil should drip out of oil drain port.
7. If oil runs out of port rapidly, allow to drain.
8. Replace oil port cap and cover.
9. Dispose of oil properly.
Oil Replacement Procedure
1. Follow steps 1 thru 4 in the oil level check.
2. Tilt unit at 45° angle towards oil drain. port until
all oil has been drained.
3. Refill with proper amount and type of oil. The
proper oil charge is 8.0 ounces 150 VISCOSITY
(SUS) POE oil.
4. Replace oil port cap and front cover.
5. Dispose of oil properly.
Note: Failure to perform oil maintenance can cause
the compressor to overfill with oil and severely
damage the compressor.
Oil
Drain
Port
Maintenance—Vacuum Pump Oil
Select ENTER to turn the reminder off until the next
time you start the unit. Select RESET to reset the
reminder until the next scheduled maintenance.
Check oil level when pump is running.
When pump is running, oil level should be 1/2 to 5/8
up in the sight glass. This level is necessary for
proper operation.
This maintenance is best performed when the oil
is warm.
1. Remove thumb screws under vacuum pump.
2. Rotate the front of the vacuum pump towards
the rear of the unit.
3. Place a container under the oil drain plug and
remove the oil drain plug.
4. Drain oil into the container.
5. Dispose of the oil properly.
6. Refill the vacuum pump with YELLOW JACKET
(Quart Part no. 93192) vacuum pump oil to the
correct level.
7. Reverse Steps 1-2.
Calibration Check (1 lb weight)
1. Select SETUP in the main menu
2. Select CALIBRATION CHECK
3. Press “START” key to stabilize
4. After stabilizing, machine will display “PLACE
THE 1lb TEST WEIGHT ON THE TANK” (1lb
weight supplied)
5. Press the “START” key
Example: 1 lb. 02 oz (Out of Calibration)
0 lb. 15.98 oz (Out of Calibration)
NOTE: If out of calibration follow the steps dis-
played on the display to recalibrate scale
“WARNING SCALE CALIBRATION” MESSAGE:
If the scale calibration changes, this message may
appear on the display. To reset the warning mes-
sage follow the on screen instructions or do the
following:
1. Select SETUP in the main menu
2. Select CALIBRATE SCALE
3. The display will then read “REMOVE WEIGHT
FROM SCALE”
4. Once the weight is removed press the START
key
5. The display will then read “CALIBRATING
PLEASE WAIT”
6. When the display reads “POWER OFF AND RE-
START SYSTEM” turn the main power switch off
7. Carefully place the tank back on the scale and
turn the main power switch back on.

14
Common Problems and Potential Solution
Problem Possible Causes Possible Solutions
37880 cannot pull au-
tomobile A/C system
into a vacuum
Service valves on hoses not properly in-
stalled
Service ball valve seals are worn.
Hoses on unit are loose or leak.
Automobile A/C system has a leak.
Check valve seals and threads and replace if need-
ed.
Replace valve seals and Schrader core depressor.
Tighten or replace hoses on unit.
Find and repair leak in A/C system.
High side gauge
readings above nor-
mal
Restriction in A/C system or Schrader
core.
Service hose ball valve closed.
Incorrect charge amount entered in unit.
Check hose connection and fix restriction. Replace
Schrader core.
Open the valve.
Recover, check scale calibration, and recharge
system.
Refrigerant not being
transferred during
Tank Refill.
Valve on supply tank closed.
Ball valve on blue service hose closed or
hose is constricted.
Wrong hose installed on new refrigerant
tank.
Storage tank is full.
Open Valve.
Open valve or straighten hose.
Install blue service hose on refrigerant tank.
Close valve on new supply. Disconnect service
hose.
Touch Pad will not
accept commands
Key on touch pad is stuck.
Bad Touch Pad.
Wire disconnected between touch pad and
microprocessor.
Microprocessor malfunction.
Feel for non-responsive key. If not responding, call
Technical Support.
Call Technical Support.
Call Technical Support.
Call Technical Support.
Fan not running in any
cycle
Loose power wire to fan.
Microprocessor malfunction.
Fan malfunction.
Locate loose fitting and reconnect.
Call Technical Support.
Call Technical Support.
Machine will not turn
on
Power cord is not plugged into a 120 Volt
outlet.
Circuit breaker tripped on shop power
panel.
Bad Main Power switch.
Loose wire.
Bad Transformer on microprocessor
board.
Plug into outlet.
Reset circuit breaker. If circuit breaker immediately
trips, do not reset. Consult a qualified electrician.
Call Technical Support.
Repair loose wire.
Call Technical Support.
Unit will not recover
refrigerant from A/C
system
Valves on service hoses shut.
Service hose is constricted.
Unit storage tank valve is closed.
Open valves.
Straighten hose.
Open tank valves.
Compressor not operating. Call Technical Support.
Unit will not charge
refrigerant into vehicle
Valves on service hoses shut
Service hose is constricted
Unit storage tank valve is closed
Open valves
Straighten hose
Open tank valves
Compressor not operating Call Technical Support.
Refrigerant leaking
during charging
Service valves on hoses not properly in-
stalled on A/C system.
Check valve seals and threads and replace if need-
ed.
Service ball valve seals are worn. Replace valve seals and Schrader core depressor
Hoses on unit are loose or leak. Tighten or replace hoses on unit
Automobile A/C system has a leak Find leak in A/C system and repair.
Troubleshooting Information
The 3788X has a number of sophisticated features which
make it by far the most user friendly A/C service system
in the world. The unit was designed for easy operation,
service and troubleshooting. Although the 3788X was
manufactured with high quality components, a compo-
nent failure could cause it to operate incorrectly.
The following section is designed to provide you with
additional information to help diagnose a system. If a
problem occurs, please read this section thoroughly
prior to calling technical support. This will reduce the
time needed to restore your system to normal operation.
Our technical support number is [phone].

15
LCD Error Messages and Potential Solution
ERROR
NUMBER
MESSAGE DESCRIPTION TROUBLESHOOTING
ERROR 1 HIGH PRESSURE HIGH PRESSURE SWITCH IS TRIPPED
(NORMALY CLOSED SWITCH)
OPEN TANK VALVE
TEST HIGH PRESSURE SWITCH
CHECK SV AND CHECK VALVE OP
CHECK TANK PRESSURE
ERROR 2 TANK FULL TANK WEIGHT OVER 80% OF CAPACI-
TY
CHECK SCALE CALIBRATION
REMOVE SOME REFRIGERANT
FROM STORAGE TANK
ERROR 3 RECOVERY TIME
OUT
RECOVERY PROCESS HAS EXCEEDED
1 HR FACTORY DEFAULT
IF AC SYSTEM CONTAINS MORE
THAN 3 LBS OF REFRIGERANT
INCREASE DEFAULT TIME
CHECK FOR LEAKS (HOSES, FIT-
TINGS AND AUTO AC SYSTEM
ERROR 4 CHARGING TIME
OUT
CHARGING PROCESS HAS EXEEDED
20 MIN FACTOR DEFAULT
OPEN TANK VALVES
OPEN SERVICE COUPLERS
SWITCH TO LOW SIDE CHARGING
CHECK TANK WEIGHT (10 LB MIN)
ERROR 5 NO TANK ON
SCALE
SCALE NOT READING TANK WEIGHT PLACE TANK ON SCALE
CHECK SCALE CALIBRATION
ERROR 6 TANK EMPTY REFRIGERANT BELOW 5 % OF
TANK CAPACITY
REFILL TANK
CHECK SCALE CALIBRATION
ERROR 7 NOT ENOUGH
REFRIGERANT
UNIT IS LOW ON REFRIGERANT
(10 LB MIN)
REFILL TANK
ERROR 8 TANK REFILL
TIME OUT
TANK REFILL HAS EXCEEDED
DEFAULT TIME
RUN TANK REFILL MODE AGAIN
CHECK FOR LEAKS
TEST LOW PRESSURE SWITCH
ERROR 9 VACUUM TIME
OUT. PLEASE
CHECK FOR
NOT USED
ERROR 10 SYSTEM
EQUALIZED
PRESSURE EQUALIZED DURING
CHARGING
INCREASE VACUUM TIME
RUN THE VEHICLE TO DRAW IN THE
REMAINING REFRIGERANT
ERROR 11 HOSE CLEARING
TIME OUT
CLEARING TIME OUT AFTER
CHARGING
CLOSE SERVICE VALVES AND DIS-
CONNECT
ERROR 12 POSSIBLE OVER
CHARGE
POTENTIAL OVERCHARGE OF THE
VEHICLE
REPEAT RECOVERY AND CHARGE
PROCESS
ERROR 13 VACUUM ERROR LP SWITCH OPENED DURRING
VACUUM HOLD
REPEAT VACUUM CYCLE
ERROR 14 LEAK CHECK
FAILD
FAILED TO HOLD VACUUM AFTER 5
ATTEMPTS
REPEAT RECOVERY PROCESS
CHECK FOR LEAKS
ERROR 15 SYSTEM
MALFUNCTION
EEP-ROM DATA READ/WRITE ERROR REPLACE MICROPROCESSOR
ERROR 16 IDENT ERROR IDENTIFIER ERROR CALL TECH-SUPPORT

16
3788X and 37837 Repair Parts List
Part # Description Part # Description
95423 High Pressure Switch 01215 R-134a Auto Low Side Blue Hose (10ft)
41301 High Side Coupler 01216 R-134a Auto High Side Red Hose (10ft)
41302 Low Side Coupler 01152 R-134a Tank Vapor Blue Hose (30in)
68950 Printer Paper 01224 R-134a Tank Liquid Red Hose (30in)
38089 Tuf-Lok™ Fasteners 19153 R-134a Tank Refill Adapter
38019 Oil Bottle 95026 50lb Refrigerant Tank
38053 Service Compressor 38003 Filter-Dryer (1 per unit)
95157 Circuit Breaker, 15 Amp 38155 Caster Wheels (2 pak)
38113 Automatic Scale Assembly
Ritchie Engineering Co., Inc.
YELLOW JACKET®Products Division
Bloomington, MN 55438 USA
Phone: [phone]
Toll Free: 800-769-8370
Fax: [phone]
Toll Free: 800-322-8684
E-mail: [e-mail]
Web Site: www.yellowjacket.com
Warranty Information
LIMITED WARRANTY
Ritchie Engineering Company, Inc. guarantees YELLOW JACKET
®products to be free of defective material and workmanship
which would affect the life of the product under normal use for the purpose for which it was designed.
This warranty does not cover items that have been altered, abused, misused, improperly maintained, or returned solely in need
of field service maintenance. This warranty expressly excludes Vacuum Pump damage and failures caused by failure to main-
tain clean, uncontaminated oil in the pump –the major reason for pump returns. Therefore, problems related to non-maintained
oil will void this warranty on that part of the product.
This warranty does not cover abuse, damage from over tightening valves, or broken gauges. “Series 41” Manifold valves can be
reconditioned using replacement seating cylinder 41133. There will be a reconditioning charge for manifolds returned to the
factory for repair.
If found defective, we will upon compliance with the return instructions either credit, replace, or repair, at our option, the defec-
tive product provided it is returned within one year of the date of factory shipment (90 days for tubing tools). NOTE: Hoses are
Date Coded to help determine age of hose. See recommended hose safety inspection procedure. Leak detectors have date of
manufacture label on product.
Correction in the manner provided above shall constitute a fulfillment of all liabilities with respect to the quality, material and
workmanship of the product. THE FOREGOING WARRANTY IS EXCLUSIVE AND IN LIEU OF ALL OTHER WARRANTIES OF
QUALITY, WHETHER WRITTEN, ORAL OR IMPLIED.
WARRANTY RETURNS - For HVAC/R Recovery Units and for Automotive Recovery, Recycle, Recharge equipment, call
1-800-769-8370 for instructions for service, repair or return. The 3788X Series units are covered by a one-year parts and labor
warranty. For all other products, please return warranty items to the main factory in Bloomington, MN, prepaid for credit,
replacement, or repair, at our option. No authorization is required. All returns must be PREPAID. On direct drive pumps, many of
the problems can be solved over the telephone. Call 952-943-1333.
NON-WARRANTY RETURNS - Prior authorization must be obtained from home office for non-warranty returns. All returns
must be PREPAID. Minimum restocking charge 20% on standard items of current date coding and manufacture. Special produc-
tion items will have a higher restocking charge. Many items shown in our price list are custom-fabricated to customer’s order.
Printed in U.S.A