Harbor Freight Tools 99780 Installation manual

OIL-LESS AIR COMPRESSOR
99780
99781
SET UP AND OPERATING INSTRUCTIONS
Visit our website at: http://www.harborfreight.com
Read this material before using this product.
Failure to do so can result in serious injury.
SAVE THIS MANUAL.
Copyright©2008 by Harbor Freight Tools®. All rights reserved. No portion of this manual or any artwork
contained herein may be reproduced in any shape or form without the express written consent of
Harbor Freight Tools. Diagrams within this manual may not be drawn proportionally. Due to continuing
improvements, actual product may differ slightly from the product described herein. Tools required for
assembly and service may not be included.
For technical questions or replacement parts, please call 1-800-444-3353.
REV 10a

SKU 99780-81 For technical questions, please call 1-800-444-3353. Page 2
SAVE THIS MANUAL
Keep this manual for the safety warn-
ings and precautions, assembly, operat-
ing, inspection, maintenance and cleaning
procedures. Write the product’s serial
number in the back of the manual near the
assembly diagram (or month and year of
purchase if product has no number). Keep
this manual and the receipt in a safe and
dry place for future reference.
IMPORTANT SAFETY
INFORMATION
In this manual, on the labeling,
and all other information provid-
ed with this product:
This is the safety alert
symbol. It is used to alert
you to potential personal
injury hazards. Obey all
safety messages that
follow this symbol to avoid
possible injury or death.
DANGER indicates
a hazardous
situation which, if not
avoided, will result in death or
serious injury.
WARNING
indicates a
hazardous situation which, if
not avoided, could result in
death or serious injury.
CAUTION, used
with the safety
alert symbol, indicates a
hazardous situation which, if
not avoided, could result in
minor or moderate injury.
NOTICE is used to
address practices
not related to personal injury.
CAUTION, without
the safety alert
symbol, is used to address
practices not related to
personal injury.
General Safety Warnings
WARNING Read all safety
warnings and instructions.
Failure to follow the warnings
and instructions may result in
explosion, re and/or serious
injury.
Save all warnings and
instructions for future reference.
Work area safety1.
Keep work area clean and well lit.a.
Cluttered or dark areas invite acci-
dents.
Do not operate tools in explosiveb.
atmospheres, such as in the pres-
ence of ammable liquids, gases
or dust. Tools become hot which
may ignite the dust or fumes.
Keep children and bystandersc.
away while operating a tool. Dis-
tractions can cause you to lose con-
trol.
Electrical safety2.
Tool plugs must match the outlet.a.
Never modify the plug in any way.
Do not use any adapter plugs with
grounded tools. Unmodied plugs
and matching outlets will reduce risk
of electric shock.
Avoid body contact with groundedb.
surfaces such as pipes, radiators,
ranges and refrigerators. There is

SKU 99780-81 For technical questions, please call 1-800-444-3353. Page 3
an increased risk of electric shock if
your body is grounded.
Do not expose tools to rain or wetc.
conditions. Water entering a tool
will increase the risk of electric shock.
Do not abuse the cord. Never used.
the cord for carrying, pulling or
unplugging the tool. Keep cord
away from heat, oil, sharp edges or
moving parts. Damaged or entan-
gled cords increase the risk of electric
shock.
If operating a tool in a damp loca-e.
tion is unavoidable, use a Ground
Fault Circuit Interrupter (GFCI)
protected supply. Use of a GFCI
reduces the risk of electric shock.
Personal safety3.
Stay alert, watch what you are do-a.
ing and use common sense when
operating this tool. Do not use
this tool while you are tired or un-
der the inuence of drugs, alcohol
or medication. A moment of inatten-
tion while operating tools may result
in serious personal injury.
Use personal protective equip-b.
ment. Always wear eye protection.
Safety equipment such as dust mask,
non-skid safety shoes, hard hat, or
hearing protection used for appropri-
ate conditions will reduce personal
injuries.
Prevent unintentional starting.c.
Ensure the switch is in the off-po-
sition before connecting to power
source or moving the tool.
Do not overreach. Keep properd.
footing and balance at all times.
This enables better control of the tool
in unexpected situations.
Dress properly. Do not wear loosee.
clothing or jewelry. Keep your
hair, clothing and gloves away
from moving parts. Loose clothes,
jewelry or long hair can be caught in
moving parts.
Only use safety equipment thatf.
has been approved by an appropri-
ate standards agency. Unapproved
safety equipment may not provide
adequate protection. Eye protection
must be ANSI-approved and breath-
ing protection must be NIOSH-ap-
proved for the specic hazards in the
work area.
Tool use and care4.
Do not force the tool. Use thea.
correct tool for your application.
The correct tool will do the job better
and safer at the rate for which it was
designed.
Do not use the tool if the switchb.
does not turn it on and off. Any
tool that cannot be controlled with
the switch is dangerous and must be
repaired.
Disconnect the plug from thec.
power source of the tool before
making any adjustments, changing
accessories, or storing tools. Such
preventive safety measures reduce
the risk of starting the tool acciden-
tally.
Store idle tools out of the reach ofd.
children and do not allow persons
unfamiliar with the tool or these
instructions to operate it. Tools are
dangerous in the hands of untrained
users.
Maintain tools. Check for mis-e.
alignment or binding of moving
parts, breakage of parts and any

SKU 99780-81 For technical questions, please call 1-800-444-3353. Page 4
other condition that may affect the
tool’s operation. If damaged, have
the tool repaired before use. Many
accidents are caused by poorly main-
tained tools.
Use the tool in accordance withf.
these instructions, taking into ac-
count the working conditions and
the work to be performed. Use of
the tool for operations different from
those intended could result in a haz-
ardous situation.
Service5.
Have your tool serviced by a quali-a.
ed repair person using only iden-
tical replacement parts. This will
ensure that the safety of the tool is
maintained.
Air Compressor Safety Warnings
1.

area or towards a hot surface. Spray
area must be well-ventilated. Do not
smoke while spraying or spray where

parts - keep compressor at least 20
feet away from explosive vapors,
such as when spraying with a spray
gun.
Risk of bursting - do not adjust2.
regulator to result in output pressure
greater than marked maximum pres-
sure of attachment.
Risk of injury - do not direct air3.
stream at body. To reduce the risk of
electric shock, do not expose to rain.
Store indoors.
Do not use to supply breathing air.4.
-5.
pressor at people or animals.
Industrial applications must follow6.
OSHA requirements.
Maintain labels and nameplates on7.
the tool. These carry important safety
information. If unreadable or miss-
ing, contact Harbor Freight Tools for a
replacement.
Avoid unintentional starting. Prepare8.
to begin work before turning on the
tool.
Do not leave the tool unattended9.
when it is plugged into an electrical
outlet. Turn off the tool, and unplug it
from its electrical outlet before leav-
ing.
This product is not a toy. Keep it out10.
of reach of children.
WARNING: The brass components11.
of this product contain lead, a chemi-
cal known to the State of California
to cause birth defects (or other repro-
ductive harm). (California Health &
Safety code § 25249.5, et seq.)
People with pacemakers should12.
consult their physician(s) before use.
-
imity to heart pacemaker could cause
pacemaker interference or pacemak-
er failure. In addition, people with
pacemakers should:


on.

avoid electrical shock.

grounded. Ground Fault Circuit Inter-
rupter (GFCI) should also be imple-

SKU 99780-81 For technical questions, please call 1-800-444-3353. Page 5
mented – it prevents sustained elec-
trical shock.
Some dust created by power sand-13.
ing, sawing, grinding, drilling, and
other construction activities, contains
chemicals known [to the State of Cali-
fornia] to cause cancer, birth defects
or other reproductive harm. Some
examples of these chemicals are:

-
ment or other masonry products
-
cally treated lumber
Your risk from these exposures var-
ies, depending on how often you do
this type of work. To reduce your
exposure to these chemicals: work in
a well ventilated area, and work with
approved safety equipment, such as
those dust masks that are specially

particles. (California Health & Safety
Code § 25249.5, et seq.)
WARNING: Handling the cord on14.
this product will expose you to lead,
a chemical known to the State of
California to cause cancer, and birth
defects or other reproductive harm.
Wash hands after handling. (Califor-
nia Health & Safety Code § 25249.5,
et seq.)
The warnings, precautions, and in-15.
structions discussed in this instruction
manual cannot cover all possible con-
ditions and situations that may occur.
It must be understood by the operator
that common sense and caution are
factors which cannot be built into this
product, but must be supplied by the
operator.
SAVE THESE
INSTRUCTIONS.
GROUNDING
TO PREVENT
ELECTRIC SHOCK
AND DEATH FROM
INCORRECT GROUNDING
WIRE CONNECTION:
Check with a qualied
electrician if you are in doubt
as to whether the outlet is
properly grounded. Do not
modify the power cord plug
provided with the tool. Never
remove the grounding prong
from the plug. Do not use the
tool if the power cord or plug
is damaged. If damaged, have
it repaired by a service facility
before use. If the plug will not
t the outlet, have a proper
outlet installed by a qualied
electrician.
Grounded Tools: Tools with Three
Prong Plugs
Tools marked with “Grounding Re-1.
quired” have a three wire cord and
three prong grounding plug. The
plug must be connected to a properly
grounded outlet. If the tool should

SKU 99780-81 For technical questions, please call 1-800-444-3353. Page 6
electrically malfunction or break
down, grounding provides a low
resistance path to carry electricity
away from the user, reducing the risk
of electric shock. (See 3-Prong Plug
and Outlet.)
The grounding prong in the plug is2.
connected through the green wire in-
side the cord to the grounding system
in the tool. The green wire in the cord
must be the only wire connected to
the tool’s grounding system and must
never be attached to an electrically
“live” terminal. (See 3-Prong Plug
and Outlet.)
The tool must be plugged into an3.
appropriate outlet, properly installed
and grounded in accordance with all
codes and ordinances. The plug and
outlet should look like those in the
preceding illustration. (See 3-Prong
Plug and Outlet.)
Symbology
Double Insulated
Canadian Standards Association

V~ Volts Alternating Current
AAmperes
n0xxxx/min. 
(RPM)
SPECIFICATIONS
Electrical Requirements 120 V~ / 60 Hz / 9.3 A
Air Hose Connection 1/4” 18 NPT
Maximum Air Pressure 155 PSI
Air Pressure Cut On 125 PSI
Air Tank Capacity sku 99780: 17 Gallons
sku 99781: 26 Gallons
Air Flow Capacity 6 SCFM @ 40 PSI
4 SCFM @ 90 PSI
Motor 4 HP, 13000 RPM
233060
UNPACKING
When unpacking, make sure that the
item is intact and undamaged. If any parts
are missing or broken, please call Harbor
Freight Tools at the number shown on the
cover of this manual as soon as possible.
INSTRUCTIONS FOR
PUTTING INTO USE
Read the ENTIRE IMPORTANT
SAFETY INFORMATION
section at the beginning of this
manual including all text under
subheadings therein before set
up or use of this product.
TO PREVENT
SERIOUS INJURY
FROM ACCIDENTAL
OPERATION:
Turn the Power Switch of the
tool to its “OFF” position and
unplug the tool from its
electrical outlet before
assembling or making any
adjustments to the tool.

SKU 99780-81 For technical questions, please call 1-800-444-3353. Page 7
Note: For additional information regarding
the parts listed in the following pages,
refer to the Assembly Diagram near
the end of this manual.
Assembly
Connect the Front Handle (25) to1.
the top of the Compressor with two
Knobs on each side. See Figure 1.
Connect the Rear Handle (18) to2.
the top of the Compressor with two
Knobs (29) on each side. See Fig-
ure1.
Connect the Front Brace (31) to the3.
bottom of the Air Tank (30). Secure
using four Knobs (29). See Figure 1.
4.
a washer (35) at the end of each Axle
(34). See Figure 2.
Put the Axles (34) in the wheel brack-5.
ets and secure them using Nut (34).
See Figure 3 below.
Put each Wheel (38) through the Axle6.
(34) on each side of the compressor.
See Figure 4.
Put a Cotter Pin (36) through the7.
ends of each Axle (34) to secure the
Wheels (38). See Figure 5.
Firmly press the Wheel Covers (37)8.
on each Wheel (38) until they snap
into place. See Figure 6.
REV 08g; 10a
Rear Handle (18)
Knobs (29)
Figure 2 Figure 3
Figure 4 Figure 5 Figure 6
Figure 1
Front
Handle (25)
Front
Brace
(31)
Wheel (38)
Knobs (29)

SKU 99780-81 For technical questions, please call 1-800-444-3353. Page 8
Connect a 1/4” NPT air hose (rated9.
155 PSI or higher) to the air con-
nection. The air hose must be long
enough to reach the work area with
enough extra length to allow free
movement while working.
Incorporate an in-line oiler, shut-off10.
valve, regulator with pressure gauge,

the diagram below. An in-line shutoff
valve is an important safety device
because it controls the air supply
even if the air hose is ruptured.
Tool
Air
Compressor
Quick
Coupler Air Hose
on Reel
Filter
Regulator with
Pressure Gauge
Male
Connector
Male
Connector
Valve
Quick
Coupler
Recommended Air Line Components
Oiler
OPERATING INSTRUCTIONS
Read the ENTIRE IMPORTANT
SAFETY INFORMATION
section at the beginning of this
manual including all text under
subheadings therein before set
up or use of this product.
TO PREVENT
SERIOUS INJURY
FROM ACCIDENTAL
OPERATION:
Turn the Power Switch of the
tool to its “OFF” position and
unplug the tool from its
electrical outlet before
performing any inspection,
maintenance, or cleaning
procedures.
Make sure the air tool’s throttle or1.
switch is in the off position.
Connect the tool that will be used for2.
the job to the airline.
Close the in-line safety valve be-3.
tween the compressor and the tool.
Connect an air hose rated to the in-4.
tended PSI that will be used with the
tool to the Air Connection. The air
hose must be long enough to reach
the work area with enough extra
length to allow free movement while
working.
Plug the Power Cord into a grounded5.
120 V electrical outlet.
Move the Power Switch to its ON6.
position.

SKU 99780-81 For technical questions, please call 1-800-444-3353. Page 9
Allow the Air Compressor to build up7.
pressure until it cycles off.
Adjust the air compressor’s Output8.
Regulator so that the air output is
enough to properly power the tool,
but the output will not exceed the
tool’s maximum air pressure at any
time. Turn the knob clockwise to
increase pressure and counter-clock-
wise to decrease pressure. Adjust
the pressure gradually, while check-
ing the air output gauge to set the
right pressure range.
The Air Compressor will cycle up to9.
155 PSI before shutting off. It will
start to build pressure again when the
PSI of the Compressor drops to 125
PSI.
If the Compressor becomes too hot10.
the circuit breaker will trip and it will
shut off. If this happens;
move the Power Switch to the OFFa.
position;
wait until the Compressor coolsb.
down;
push the Circuit Breaker button;c.
turn Power Switch back to the ONd.
position and resume operation.
After the job is complete, move the11.
Power Switch to the OFF position.
Pull up on the Safety Valve to release12.
pressure in the tank. Squeeze the
Trigger of the air tool to release pres-
sure from the line
Turn the Drain Valve at the bottom13.
of the Tank two turns to release any
built-up moisture. Close the valve
after moisture has drained out. Do
not remove the Drain Valve.
Drain Valve
14. Disconnect the air hose and tool.
To prevent accidents, disconnect its15.
power supply after use. Clean, then
store the tool indoors out of children’s
reach.
REV 10a
PSI Gauge of
Compressor
Safety
Valve
Power
Switch
Circuit
Breaker
Output
Regulator
PSI Gauge
for Tool
Air
Outlet
Connection

SKU 99780-81 For technical questions, please call 1-800-444-3353. Page 10
MAINTENANCE AND
SERVICING
Procedures not specically
explained in this manual
must be performed only by a
qualied technician.
TO PREVENT
SERIOUS INJURY
FROM ACCIDENTAL
OPERATION:
Turn the Power Switch of the
tool to its “OFF” position and
unplug the tool from its
electrical outlet before
performing any inspection,
maintenance, or cleaning
procedures.
TO PREVENT SERIOUS
INJURY FROM TOOL
FAILURE:
Do not use damaged
equipment. If abnormal noise
or vibration occurs, have the
problem corrected before
further use.
Cleaning, Maintenance, and
Lubrication
BEFORE EACH USE,1. inspect the
general condition of the tool. Check
for loose screws, misalignment or
binding of moving parts, cracked or
broken parts, damaged electrical wir-
ing, and any other condition that may
affect its safe operation.
AFTER USE,2. clean external surfaces
of the tool with clean cloth.
3. WARNING! If the supply cord of
this power tool is damaged, it must
be replaced only by a qualied
service technician.
PLEASE READ THE FOLLOWING
CAREFULLY
THE MANUFACTURER AND/OR DISTRIBUTOR



MANUFACTURER OR DISTRIBUTOR MAKES
ANY REPRESENTATION OR WARRANTY OF
ANY KIND TO THE BUYER THAT HE OR SHE



IN FACT, THE MANUFACTURER AND/OR











SKU 99780-81 For technical questions, please call 1-800-444-3353. Page 11
PARTS LIST
Part Description Qty.
1 Cover 1
2 Power Switch 1
3 Overload Protector 1
4 Screw ST4.2x25 6
5 Upper Housing 1
6 Cord Plate 1
7 Screw ST3.5x16 4
8 Motor/Pump Assembly 1
9 Screw 3
10 Washer 3
11 Bolt 3
12 Washer 3
13 Bracket Washer 3
14 Regulator 1
15 Screw ST4x18 4
16 Screw ST4x20 2
17 Cord Retainer 1
18 Rear Handle 1
19 Connector 1
20 Valve 1
PARTS LIST
Part Description Qty.
21 Pressure Control 1
22 Zip Tie 2
23 Wire 1
24 Power Cord 1
25 Front Handle 1
26 Tube 1
27 Tube 1
28 Hoop 1
29 Knob 12
30 Air Tank 1
31 Front Brace 1
32 Drain Valve 1
33 Nut M8 1
34 Axle 2
35 Washer 2
36 Cotter Pin 2
37 Wheel Cover 2
38 Wheels 2
39 Screw M5x8 1

SKU 99780-81 For technical questions, please call 1-800-444-3353. Page 12
ASSEMBLY DIAGRAM
Record Product’s Serial Number Here:
Note: If product has no serial number, record month and year of purchase instead.
Note: Some parts are listed and shown for illustration purposes only, and are not avail-
able individually as replacement parts.

SKU 99780-81 For technical questions, please call 1-800-444-3353. Page 13
LIMITED 1 YEAR / 90 DAY WARRANTY
Harbor Freight Tools Co. makes every effort to assure that its products meet high qual-
ity and durability standards, and warrants to the original purchaser that for a period of one year
from date of purchase that the tank is free of defects in materials and workmanship (90 days
if used by a professional contractor or if used as rental equipment). Harbor Freight Tools also
warrants to the original purchaser, for a period of ninety days from date of purchase, that all
other parts and components of the product are free from defects in materials and workmanship.
This warranty does not apply to damage due directly or indirectly to misuse, abuse, negligence
or accidents, repairs or alterations outside our facilities, normal wear and tear, or to lack of
maintenance. We shall in no event be liable for death, injuries to persons or property, or for inci-
dental, contingent, special or consequential damages arising from the use of our product. Some
states do not allow the exclusion or limitation of incidental or consequential damages, so the
above limitation of exclusion may not apply to you. 


To take advantage of this warranty, the product or part must be returned to us with trans-
portation charges prepaid. Proof of purchase date and an explanation of the complaint must

the product at our election or we may elect to refund the purchase price if we cannot readily and
quickly provide you with a replacement. We will return repaired products at our expense, but if
we determine there is no defect, or that the defect resulted from causes not within the scope of
our warranty, then you must bear the cost of returning the product.

from state to state.
3491 Mission Oaks Blvd. • PO Box 6009 • Camarillo, CA 93011 • [phone]
Troubleshooting
Problem Possible Causes Likely Solutions
Overheating Poor ventilation.1.
Dirty cooling surfaces.2.
Compressor undersized for3.
application.
Move the compressor to an area with better1.
air circulation.
Clean compressor.2.
Check air requirements of tools.3.
Compressor
operates, but with
low air output
Valve or regulator loose or1.
leaking.
Valve or regulator damaged.2.
Air tank not pressurized yet.3.
Repair leaks.1.
Have valve or regulator repaired by a2.

Allow pressure to build.3.
Incorrect pressure
gauge reading
Pressure gauge worn or1.
damaged.
1.
technician.
Follow all safety precautions whenever diagnosing or servicing the
tool. Disconnect air supply before service.