Nilfisk-Advance SR 1900 User manual

SR 1900
Service Manual
Cab Addendum
11/08
FORM NO. 56043123
Printed in USA
Models:
56508769 (4 cyl LPG), 56508770 (4 cyl Petrol), 56508771 (4 cyl Diesel)

CONTENTS
Contents ............................................................................................................................................................................... iii
Figures..................................................................................................................................................................................iv
Section 1 — Introduction................................................................................................................................................ 1-3
SR 1900 Deluxe Cab Options ...............................................................................................................................................1
Other Manuals Available........................................................................................................................................................1
General Notes .......................................................................................................................................................................1
Cautions and Warnings .........................................................................................................................................................2
Symbols.................................................................................................................................................................................2
General Safety Instructions ...................................................................................................................................................2
Technical Specifications ........................................................................................................................................................3
Section 2 — Know Your Machine................................................................................................................................... 4-6
Cab Controls..........................................................................................................................................................................4
Heating System Components................................................................................................................................................5
Air Conditioning System Components...................................................................................................................................6
Section 3 — Maintenance ...................................................................................................................................................7
Maintenance Schedule..........................................................................................................................................................7
To Clean and Replace the Cab Filter.....................................................................................................................................7
Section 4 — Heating System........................................................................................................................................ 8-12
General System Overview.....................................................................................................................................................8
Electrical Circuit Overview.....................................................................................................................................................8
Heater Blower Motor..............................................................................................................................................................8
Heater Temperature Control ..................................................................................................................................................8
Electrical Troubleshooting ................................................................................................................................................9-11
Symptom: The heater Blower Motor will not run....................................................................................................................9
Symptom: There is no cab heat, or the cab heat cannot be controlled. .........................................................................10-11
To Eliminate Air Locks from the Cooling System.................................................................................................................12
Cooling System Vacuum Filler.............................................................................................................................................12
Purge the Heater Circuit......................................................................................................................................................12
Section 5 — Air Conditioning System ....................................................................................................................... 13-20
General System Overview...................................................................................................................................................13
Electrical Circuit Overview...................................................................................................................................................13
Blower Motors......................................................................................................................................................................13
Condenser Fan, Thermostat, Pressure Switch and Compressor Motor..............................................................................14
Electrical Troubleshooting ...................................................................................................................................................15
Symptom: One or both of the Blower Motors will not run. ...................................................................................................15
Symptom: The Blower Motors run but there is no cold air coming out of the Evaporator-Heater Unit................................16
Component Troubleshooting ...............................................................................................................................................17
Compressor Motor Hydraulic Valve (L10)............................................................................................................................17
Accessory (Gear) Hydraulic Pump ......................................................................................................................................17
Compressor Relay (K10).....................................................................................................................................................18
Binary Pressure Switch (S34)..............................................................................................................................................19
Thermostat (S33).................................................................................................................................................................20
Section 6 — Appendix.......................................................................................................................................................21
Cab Electrical Wiring Diagram.............................................................................................................................................21
Cab Electrical Ladder Diagram............................................................................................................................................22
Heating and A/C System Plumbing and Hydraulic Schematic.............................................................................................23
FIGURES
Figure 1-1 — SR 1900 Cab Height........................................................................................................................................3
Figure 2-1 — Cab Controls....................................................................................................................................................4
Figure 2-2 — Heating System Components..........................................................................................................................5
Figure 2-3 — Air Conditioning System Components.............................................................................................................6
Figure 3-1 — Cab Filter.........................................................................................................................................................7
Figure 4-1 — Valve Assembly Connector Pins....................................................................................................................10
Figure 4-2 — Valve Assembly Hose Functions ...................................................................................................................12
Figure 5-1 — Compressor Motor Hydraulic Valve...............................................................................................................17
Figure 5-2 — Compressor Relay.........................................................................................................................................18
Figure 5-3 — Checking Continuity through the Binary Pressure Switch .............................................................................19
Figure 5-4 — Checking Continuity through the Thermostat ................................................................................................20

FORM NO. 56043123 - SR 1900 - 1
SECTION 1 — INTRODUCTION
SR 1900 DELUXE CAB OPTIONS
The SR 1900 Deluxe Cab is available with two levels of environmental control that provide additional comfort and convenience for the Operator, and add additional
functionality to the machine.
An optional cab heater is available which includes a pressurized cab with an external air filter.
An optional heating and air conditioning system is available that provides Operator comfort throughout a wide range of ambient temperatures.
OTHER MANUALS AVAILABLE
This service manual includes instructions and information to help you to maintain, troubleshoot and repair the cab heating and air conditioning systems.
This manual is meant to be used in conjunction with the following manuals and information sources for the SR 1900 Rider Sweeper and Cab.
General Information
Nilfisk-Advance website (www.nilfisk-advance.com)
SR 1900 Cab Manuals Form Number
Cab Addendum 56041710
Parts List – Cab Addendum 56042486
SR 1900 Manuals Form Number
Parts List (all systems w/optional kits & accessories) 56042471
Operation Manual (English, Spanish) 56041656
Operation Manual (Danish, Norway, Swedish, Finnish) 56041661
Operation Manual (German, French, Dutch, Russian) 56041662
Operation Manual (Spanish, Portuguese, Italy, Greek) 56041663
Operation Manual (Estonian, Latvian, Lithuanian, Slovenian) 56041664
Operation Manual (Slovakian, Czech, Polish, Hungarian) 56041665
Operation Manual (Turkish) 56041666
Quick Start Troubleshooting Manual 56043110
Engine Manuals
1.6L Industrial Engine Operator Manual (excerpt from 16LECSS), Nilfisk form number 56041564
1.6L Industrial Engine Service Manual 36100009*
PSI 1.6L PFI Tier II Certified Engine Service Manual, publication number PSI1P6LPFI-A (available in electronic format only)
V1505 Kubota Diesel Engine Service Manual (WSM English) 97897-02432
V1505 Kubota Diesel Engine Service Manual (WSM English, French, German) 97897-01640
V1505 Kubota Diesel Engine Operator Manual (English, French, German, Italian, Spanish) 16622-8916-3
GENERAL NOTES
As you read this manual you will occasionally run across a bold number or letter in parentheses, for example “(2)”. These numbers refer to items shown on the
following pages. Refer to Section 2 — Know Your Machine for the location of items highlighted in bold in the text.
Note: All references to right, left, front, or rear in this manual are as seen from the operator’s position.

2- FORM NO. 56043123 - SR 1900
CAUTIONS AND WARNINGS
SYMBOLS
Nilfisk uses the symbols below to signal potentially dangerous conditions. Read this information carefully and take the necessary
steps to protect personnel and property.
DANGER!
Is used to warn of immediate hazards that will cause severe personal injury or death.
WARNING!
Is used to call attention to a situation that could cause severe personal injury.
CAUTION!
Is used to call attention to a situation that could cause minor personal injury or damage to the machine or other property.
Read all instructions before using.
GENERAL SAFETY INSTRUCTIONS
Specific Dangers, Warnings and Cautions are included to warn you of potential danger of machine damage or bodily harm.
DANGER!
This machine emits exhaust gases (carbon monoxide) that can cause serious injury or death. Always provide adequate ventilation
when using machine.
WARNING!
Remove all jewelry when working near electrical components.
Turn the key switch off (O) and disconnect the battery before servicing electrical components.
Never work under a machine without safety blocks or stands to support the machine.
Do not dispense flammable cleaning agents, operate the machine on or near these agents, or operate in areas where flammable
liquids exist.
CAUTION!
Before performing any service function, carefully read all instructions pertaining to that function.
Do not leave the machine unattended without first turning the key switch off (O), removing the key and securing the machine.
Turn the key switch off (O) and remove the key before changing the brooms and before opening any access panels.
Take precautions to prevent hair, jewelry or loose clothing from becoming caught in moving parts.
Close and secure all doors, covers and access panels as shown in the SR 1900 Instructions For Use before using the machine.
Do not clean the cab with a pressure washer. We recommend hand-washing the cab using normal “garden hose” water pressure.
Do not spray water directly at or into the cab filter or any electrical components. Allow the machine to dry completely before use.
SAVE THESE INSTRUCTIONS

FORM NO. 56043123 - SR 1900 - 3
TECHNICAL SPECIFICATIONS
Total Machine Height with Cab
(Refer to Figure 1-1 below.)
79.5 in (202 cm) without Amber Strobe Kit
84.5 in (215 cm) with Amber Strobe Kit installed
System Voltage 12 VDC
Heater Temperature Control Electronic Water Valve w/Bypass
Blower Motors
Heating System (1) Fasco OEM p/n 2807-510-154, Fasco p/n DC136, 1/8 HP, 4200
RPM, three-speed, 4.5 Amp
A/C System (2) SPAL type 008-A37/C-42D, 4.5 Amp
Refrigerant R-134a, 1.3 lbs.
Condenser Fan Motor SPAL, type VA13-AP9/C-35S, 6.9 Amp
Compressor ICE TM-08-HD, 5 cu. in. (82.0 cc) per revolution, 700-6000 RPM
Compressor Motor Sauer-Danfoss p/n 121.20.045.00, 1.02 cu. in. (16.7 cc)
displacement
Heating System Capacity 20,000 BTUs/hr.
Air Conditioning System Capacity 13,000 BTUs/hr.
FIGURE 1-1 – SR 1900 Cab Height

4- FORM NO. 56043123 - SR 1900
SECTION 2 — KNOW YOUR MACHINE
CAB CONTROLS
Refer to Figure 2-1.
1 Cooling Fan Switch
2 Dome Light
3 Heater A/C Fan Switch
4 Heater Temperature Control
5 A/C On/Off Switch
6 Windshield Wiper Switch
FIGURE 2-1 – Cab Controls

FORM NO. 56043123 - SR 1900 - 5
HEATING SYSTEM COMPONENTS
Refer to Figure 2-2
7 Blower Motor
8 Blower Assembly
9 Heater Core
10 Heater Air Box Assembly
11 Filter
12 Coolant Tube (From Engine Radiator)
13 Cab Filter Cover
14 Heater Hoses
15 Heater Control Assembly
16 HVAC Relay
FIGURE 2-2 – Heating System Components

6- FORM NO. 56043123 - SR 1900
AIR CONDITIONING SYSTEM COMPONENTS
Refer to Figure 2-3
17 Evaporator-Heater Unit
18 A/C Condenser
19 Binary Pressure Switch
20 A/C Receiver/Dryer
21 A/C Compressor
22 Hydraulic Compressor Motor
23 Air Filter
24 Cab Filter Cover
25 Coolant Tube (From Engine Radiator)
26 Heater Hoses
27 Heater Control Assembly
28 Accessory (Gear) Hydraulic Pump
29 Compressor Motor Hydraulic Valve
30 Compressor Relay
31 HVAC Relay
FIGURE 2-3 – Air Conditioning System Components

FORM NO. 56043123 - SR 1900 - 7
SECTION 3 — MAINTENANCE
WARNING!
Turn the key switch off and remove the key from the ignition switch before performing any machine maintenance.
MAINTENANCE SCHEDULE
Maintenance intervals given are for average operating conditions. Machines used in severe operational environments may require service more often.
Maintenance Item Daily Weekly Monthly Hours
Check for any coolant, hydraulic or refrigerant leaks.
Note: Refrigerant leaks can appear as dirty, oily areas around A/C
components and fittings.
X 8-12
Check the cab filter and clean or replace as necessary.
Note: The cab filter may need to be cleaned or replaced more often if the
machine is operated in dusty environments.
X40
Clean the heater core fins and air box (heater only). X 160
Clean the evaporator and heater core fins inside the evaporator-heater unit
(A/C only). X 160
Clean the condenser fins (A/C only). X 40
TO CLEAN AND REPLACE THE CAB FILTER
Refer to Figure 3-1.
Remove the four screws holding the1. Cab Filter Cover, then remove the Cab Filter Cover and Filter from the machine.
Clean the2. Filter using any of the following methods:
Tap the Filter gently on a flat surface (dirty side down).
Clean the Filter with compressed air (100 psi max.) blown from the inside (cab side) of the Filter.
Soak the Filter in warm water for 15 minutes, rinse with clean water (40 psi max. water pressure), then air-dry (don’t use compressed air). Make sure the
Filter is completely dry before reinstalling.
Reinstall the3. Filter and Cab Filter Cover, then reinstall and tighten the four screws.
FIGURE 3-1 – Cab Filter

8- FORM NO. 56043123 - SR 1900
SECTION 4 — HEATING SYSTEM
Note: Refer to Section 2 — Know Your Machine and the schematics in Section 6 — Appendix.
GENERAL SYSTEM OVERVIEW
The SR 1900 cab heating system uses an electronic Heater Control Assembly (15) to direct the appropriate amount of engine coolant to the Heater Core (9) in the
Heater Air Box Assembly (10). The Blower Assembly (8) in the Heater Air Box Assembly blows filtered air through the Heater Core to provide warm air to the cab.
A four-port bypass butterfly valve in the Heater Control Assembly, run by a small electric motor, controls the coolant flow to the Heater Core. The Heater
Temperature Control (4) in the cab controls the voltage to the valve motor, and uses a feedback potentiometer to sense the position of the butterfly valve.
ELECTRICAL CIRCUIT OVERVIEW
Heater Blower Motor
The following conditions must be met for the blower motor to function:
Positive (+) Voltage
The key switch (S1)must be in either the accessory or ignition position to provide +12 VDC (GRN/BLU wire) to the 20A circuit breaker CB4.
Circuit breaker CB4 must be closed to provide +12 VDC (VIO wire) to the control side (coil) of the HVAC Relay K8.
The 20A circuit breaker CB9 must be closed to provide voltage (RED/VIO wire) to the input load side of the HVAC Relay K8.
HVAC Relay K8 must be closed to provide +12 VDC (VIO/GRAY wire) to the positive terminal on the Fan Switch S30.
The Fan Switch S30 must be set to the Low (YEL wire), Medium (RED wire) or High (ORN wire) position to provide +12 VDC to the corresponding terminal on
the Blower Motor M6.
Negative (–) Voltage
The Blower Motor M6 must be connected to battery negative (BLK wire).
The control side (coil) of the HVAC Relay K8 must be connected to battery negative (BLK wire).
Heater Temperature Control
The following conditions must be met for the heater temperature control to function:
Positive (+) Voltage
The key switch must be in either the accessory or ignition position to provide +12 VDC (GRN/BLU wire) to the 20A circuit breaker CB4.
Circuit breaker CB4 must be closed to provide +12 VDC (VIO wire) to the control side (coil) of the HVAC Relay K8.
The 20A circuit breaker CB9 must be closed to provide voltage (RED/VIO wire) to the input load side of the HVAC Relay K8.
HVAC Relay K8 must be closed to provide +12 VDC (VIO/GRAY to RED wire) to the Heater Temperature Control E1.
Negative (–) Voltage
The Heater Temperature Control E1 (BLK wire) must be connected to battery ground.
The control side (coil) of the HVAC Relay K8 must be connected to battery negative (BLK wire).

FORM NO. 56043123 - SR 1900 - 9
ELECTRICAL TROUBLESHOOTING
Note: Refer to the Electrical Wiring and Ladder Diagrams in Section 6 — Appendix.
Symptom: The heater Blower Motor will not run.
Is there continuity through
20A circuit breaker CB9?
No
Yes
Is there 12V at the VIO/GRA
wire on the Fan Switch S30? (ref.
to bat. neg. w/key switch on)
Does the resistance of
Relay coil K8 measure 85:
±20%?
Is there continuity through
the load contacts on K8
(terminals 30 and 87) when
the coil is energized?
Is there continuity through
20A circuit breaker CB4?
Is there voltage at each of the
three positive terminals on Fan
Switch S30 when the Switch is
set to the corresponding fan
speed? (YEL, RED and ORN
wires ref. to bat. neg.)
Yes
Replace the Fan
Switch S30.
No
Replace the Blower
Motor M6.
The Blower Motor is not
working.
Is there continuity in the YEL,
RED and ORN wires from Fan
Switch S30 to the positive
terminals on the Blower Motor
M6?
No Repair the
wires.
Yes
Is there 12V in the BLK wire
from the negative terminal on the
Blower Motor M6 ref. to bat.
pos.?
Yes
No Repair the wire.
Yes
Reset or replace
circuit breaker
CB4.
No
Reset or replace
circuit breaker
CB9.No
Yes
Yes
Replace the Relay. No
Replace the relay. No
Yes
Check the connectors and
wiring and repair as
necessary.

10 - FORM NO. 56043123 - SR 1900
Symptom: There is no cab heat, or the cab heat cannot be controlled.
Note: Before troubleshooting the heating system, make sure the engine is up to normal operating temperature, the engine coolant is at the recommended level
and there are no air locks in the cooling system. (Refer to the To Eliminate Air Locks from the Cooling System subsection.)
To Troubleshoot the Valve Assembly
Refer to Figure 4-1.
FIGURE 4-1 – Valve Assembly Connector Pins
Valve Open to Heater Core, Heater
Temperature Control set to Hot (full
clockwise)
Ohmmeter Connections Resistance (Approximate)
Feedback (+) Pin and Feedback (-) Pin 5.71 k
Feedback (+) Pin and Feedback Pot Pin 5.55 k
Feedback Pot Pin and Feedback (-) Pin 0.88 k
Valve Closed to Heater Core, Heater
Temperature Control set to Cold (full
counterclockwise)
Feedback (+) Pin and Feedback (-) Pin 5.71 k
Feedback (+) Pin and Feedback Pot Pin 0.48 k
Feedback Pot Pin and Feedback (-) Pin 5.63 k
Valve Halfway Open, Heater Temperature
Control set to approximate midpoint
Feedback (+) Pin and Feedback (-) Pin 5.71 k
Feedback (+) Pin and Feedback Pot Pin 3.14 k
Feedback Pot Pin and Feedback (-) Pin 3.25 k
If the6. Feedback Pin resistance values are not close to those shown in the above table, it indicates that the feedback potentiometer in the Valve Assembly is
not working correctly. Replace the Valve Assembly.
Valve Assembly
Feedback (+) Pin
Feedback Pot Pin
Feedback (-) Pin
Motor (+) Pin
Motor (-) Pin
Disconnect the electrical connector from the1. Valve Assembly.
Carefully connect a 12 VDC source to the2. Motor (-) and
Motor (+) pins (directly or via the BLK/WHT and ORN wires in
the connector) to run the butterfly valve motor independently
without input from the heater temperature control.
Check for the heated coolant being switched on and off to3.
the heater core. Note that it will take approximately 15-20
seconds for the valve motor to run between its full-off and
full-on positions.
●If the valve motor isn’t running, replace the4. Valve
Assembly.
●If the valve motor appears to be running correctly,
continue on to step 5 below.
Check the resistance through the5. Feedback Pins to
determine if the feedback potentiometer in the Valve
Assembly is working correctly. The resistance values should
be close to those shown in the table below.

FORM NO. 56043123 - SR 1900 - 11
TO TROUBLESHOOT THE HEATER TEMPERATURE CONTROL
Service Tip: If you have to replace the Heater Temperature Control in the cab, we recommend that you do so as follows:
Remove the Overhead Control Plate from the cab.1.
Disassemble the Heater Temperature Control from the Overhead Control Plate.2.
Cut the seven wires going to the Heater Temperature Control at the point where they enter the sealed back of the module.3.
Check the continuity of the five wires going to the Valve Assembly (VIO, WHT, GRN, GRA/BLK WHT, and ORN).4.
If there is continuity in all five wires from the cab to the Valve Assembly, continue to step 5.
If there is no continuity in any of the five wires from the cab to the Valve Assembly, you will need to either repair the wires or run new wires to the Valve
Assembly.
Install the replacement Heater Temperature Control on the Overhead Control Plate.5.
Splice the original wires from the Valve Assembly to the replacement Heater Temperature Control using butt connectors and heat-shrink insulation.6.
Reinstall the Overhead Control Plate in the cab.7.
Yes
Is there 12V to the Heater
Temperature Control (BLK and
RED wires)?
Is there approximately +/- 9.75V
at the Valve Assembly
Connector (BLK/WHT and
ORN wires) when the Heater
Temperature Control E1 is
rotated between cold and hot?
Check the wiring to the Heater
Temperature Control and repair
as necessary.
There is no Cab heat/the Cab
heat cannot be controlled.
Is there continuity in the three
feedback pot wires (WHT, VIO and
GRN) from the Heater Temperature
Control to the Valve Assembly
Connector?
Replace the Heater
Temperature Control.
No
No
No
Yes
Is there continuity in all five
wires from the Heater
Temperature Control to the Valve
Assembly Connector?
Yes
No Repair the wiring
as necessary.
Replace the Heater
Temperature Control.
Repair the wiring
as necessary.
Yes

12 - FORM NO. 56043123 - SR 1900
TO ELIMINATE AIR LOCKS FROM THE COOLING SYSTEM
Air locks (air bubbles) in the cooling system can prevent normal coolant flow to the heater core. One factor that can contribute to the formation of air locks is the
fact that the heater cores in the SR 1900 cabs are the highest point in the machine’s cooling system. This can make it difficult to purge the air from the system
using traditional methods more common to the automotive industry.
Cooling System Vacuum Filler
One recommended method for removing air locks is to drain the cooling system completely, then refill the system using a cooling system vacuum filler tool. This
type of tool uses a Venturi vacuum generator to remove the air from the radiator as it fills the radiator with coolant.
Purge the Heater Circuit
Refer to Figure 4-2.
Another method is to remove the hoses that run from the Valve Assembly to the heater core, purge the hoses with coolant to remove as much air as possible from
the heater circuit, reinstall the hoses, then run the machine with the heater on to purge any remaining air from the system.
Figure 4-2 shows the heater hose functions for reference.
WARNING!
Before attempting to remove the heater hoses, make sure:
The engine is switched off.
The machine coolant has cooled to a low enough temperature so as not to cause burns or injury to persons contacting the hoses or coolant.
The cooling system temperature and pressure have decreased enough to allow you to remove the radiator cap to relieve the system pressure before removing
the hoses.
FIGURE 4-2 – Valve Assembly Hose Functions
Coolant Return
to Engine
Coolant Return
from Heater Core
Coolant Supply
from Engine
Coolant Supply
to Heater Core

FORM NO. 56043123 - SR 1900 - 13
SECTION 5 — AIR CONDITIONING SYSTEM
Note: Refer to Section 2 — Know Your Machine and the schematics in Section 6 — Appendix.
General System Overview
The SR 1900 cab air conditioning system uses a Hydraulic Compressor Motor (22), powered by the Gear (Accessory) Hydraulic Pump (28), to run the A/C
Compressor (21). The A/C Compressor compresses the refrigerant and transfers the hot, high-pressure refrigerant gas to the A/C Condenser (18) at the rear
of the machine which condenses the refrigerant gas into a liquid. The condensed high-pressure liquid refrigerant travels from the A/C Condenser to the A/C
Receiver/Dryer (20), then to the expansion valve and evaporator inside the Evaporator-Heater Unit (17) inside the cab. The cold, low-pressure refrigerant gas then
returns to the A/C Compressor to complete the refrigeration cycle.
The Operator moderates the cab cooling by “mixing in” heated air from the heater core in the Evaporator-Heater Unit by adjusting the Heater Temperature Control
(4).
The Thermostat (S33) (normally closed) has a temperature probe that is inserted into the evaporator coil in the Evaporator-Heater Unit. When the temperature of
the evaporator coil reaches 39.5°F, the Thermostat closes to enable the A/C system. When the temperature of the evaporator coil drops to 31°F, the Thermostat
opens to switch off the A/C system.
The Binary Pressure Switch (S34) (19) (normally closed), located on top of the A/C Receiver/Dryer, will interrupt the +12 VDC to the Compressor Motor Hydraulic
Valve (L10) (29) to switch off the Hydraulic Compressor Motor and A/C Compressor under the following two conditions:
The refrigerant line pressure drops below 30 psig, indicating an insufficient amount of refrigerant in the system.
The refrigerant line pressure rises above 270 psig, indicating an overheated or unsafe condition.
The Compressor Relay (K10) (30) will interrupt the +12 VDC to the Compressor Motor Hydraulic Valve (L10) to switch off the Hydraulic Compressor Motor and A/C
Compressor whenever the hopper is raised.
Electrical Circuit Overview
Blower Motors
The following conditions must be met for the blower motors to function:
Positive (+) Voltage
The key switch must be in either the accessory or ignition position to provide +12 VDC (GRN/BLU wire) to the 20A circuit breaker CB4.
Circuit breaker CB4 must be closed to provide +12 VDC (VIO wire) to the control side (coil) of the HVAC Relay K8.
The 20A circuit breaker CB9 must be closed to provide voltage (RED/VIO wire) to the load side of the HVAC Relay K8.
The HVAC Relay K8 must be closed to provide +12 VDC (VIO/GRAY wire) to the positive terminal on the Fan Switch S30.
The Fan Switch S30 must be set to the Low (YEL wire), Medium (RED wire) or High (ORN wire) position to provide +12 VDC to the corresponding terminals
on the Blower Motors M9 and M10.
Negative (–) Voltage
The Blower Motors M9 and M10 must be connected to battery negative (BLK wires).
The control side (coil) of the HVAC Relay K8 must be connected to battery negative (BLK wire).

14 - FORM NO. 56043123 - SR 1900
CONDENSER FAN, THERMOSTAT, PRESSURE SWITCH AND COMPRESSOR MOTOR
The following conditions must be met for the air conditioning system to function:
Positive (+) Voltage
The key switch must be in either the accessory or ignition position to provide +12 VDC (GRN/BLU wire) to the 20A circuit breaker CB4.
Circuit breaker CB4 must be closed to provide +12 VDC (VIO wire) to the control side (coil) of the HVAC Relay K8.
The 20A circuit breaker CB9 must be closed to provide voltage (RED/VIO wire) to the load side of the HVAC Relay K8.
HVAC Relay K8 must be closed to provide +12 VDC (VIO/GRA wire) to the positive terminal on the Fan Switch S30.
The Fan Switch S30 must be set to the Low, Medium or High position to provide +12 VDC (RED/WHT wire) to the AC Switch S35.
The AC Switch S35 must be closed to provide +12 VDC to:
The control side (coil) of the Condenser Fan Relayo K9 (WHT wire).
The input terminal on the Thermostato S33 (BLK/WHT wire).
The Thermostat S33 (normally closed) must be closed to provide +12 VDC (GRN wire) to the input terminal on the Pressure Switch S34.
The Binary Pressure Switch S34 (normally closed) must be closed to provide +12 VDC (GRN/WHT wire) to the load side of the Compressor Relay K10
(terminal 30).
The load side of the Compressor Relay K10 (normally closed) must be closed to provide +12 VDC (BLU/BRN wire from terminal 87a) to the Compressor
Hydraulic Valve L10.
Note: The Compressor Relay K10 coil (control side) is wired in parallel with the Hopper Up/Down Hydraulic Valve L5. When the Raise Hopper switch is pressed,
it actuates the Hopper Up/Down Hydraulic Valve L5 to raise the hopper, and actuates the Compressor Relay K10 coil to open the circuit to the Compressor
Hydraulic Valve L10 and switch off the A/C compressor motor. This feature allows the machine to use the maximum available hydraulic force to raise the hopper.
Negative (–) Voltage
The control side (coil) of the Condenser Fan Relay K9 must be connected to battery negative (BLK wire).
The control side (coil) of the Compressor Hydraulic Valve L10 must be connected to battery negative (BLK wire).
The control side (coil) of the HVAC Relay K8 must be connected to battery negative (BLK wire).

FORM NO. 56043123 - SR 1900 - 15
ELECTRICAL TROUBLESHOOTING
Note: Refer to the Cab Electrical Wiring and Ladder Diagrams in Section 6 — Appendix.
Symptom: One or both of the Blower Motors will not run.
No
Yes
Yes
No
No
Yes
Yes
No
Yes
No
No
Yes
Yes
No
No
Yes
Is there continuity through
20A circuit breaker CB9?
Is there 12V at VIO/GRA wire
on Fan Switch S30? (ref. to bat.
neg. w/key switch on)
Does the resistance of
Relay coil K8 measure 85:
±20%?
Is there continuity through
the load contacts on K8
(terminals 30 and 87) when
the coil is energized?
Is there continuity through
20A circuit breaker CB4?
Is there voltage at each of the
three positive terminals on Fan
Switch S30 when the Switch is
set to the corresponding fan
speed? (YEL, RED and ORN
wires ref. to bat. neg.) Replace the Fan
Switch.
Replace Blower
Motor M9 and/or
M10.
One or both of the Blower
Motors will not run.
Is there continuity in the YEL,
RED and ORN wires from Fan
Switch S30 to positive terminals
on Blower Motors M9 and M10?Repair the
wires.
Is there 12V in the BLK wire
from negative terminal on
Blower Motors M9 and M10 ref.
to bat. pos.? Repair the
wire(s).
Reset or replace
circuit breaker
CB4.
Reset or replace
circuit breaker
CB9.
Replace the Relay.
Replace the Relay.
Check the connectors and
wiring and repair as
necessary.

16 - FORM NO. 56043123 - SR 1900
Symptom: The Blower Motors run but there is no cold air coming out of the Evaporator-Heater Unit.
Note: Before troubleshooting the air conditioning system, make sure the system is filled with the recommended amount of refrigerant. We recommend that you
have this checked by a qualified technician or an EPA-certified air conditioning repair shop.
Note: Refer to the Cab Electrical Wiring and Ladder Diagrams in Section 6 — Appendix, and the Component Troubleshooting subsections on the following
pages.
Is there 12V at the GRN wire on
the Thermostat S33 (ref. to bat.
neg.)?
Is there 12V at the WHT wire on
A/C Switch S35 (ref. to bat. neg.
w/A/C Switch S35 on)?
Is there 12V at the GRN/WHT
wire on the Pressure Switch S34
(ref. to bat. neg.)?
Is there 12V across the coil on
the Compressor Hydraulic Valve
L10 (hopper down, A/C
switched on)?
There is no cold air from
the Evaporator-Heater
Unit.
Yes
Check/replace A/C
Switch S35.No
Check/replace
Thermostat S33.No
Yes
Yes
The A/C system is
overheated. Check the
Condenser Fan Relay K9,
Condenser Fan and associated
wiring and replace/repair as
necessary.
No
Check the cartridge on
Hydraulic Valve L10 and
clean/replace as necessary.
Is there 12V at the BLU/BRN
wire on the Compressor Relay
K10 (ref. to bat. neg. with the
Hopper down)?
Check the function of the
Compressor Relay K10 and
wiring and repair/replace as
necessary.
No
No
Yes
Yes
Is the hydraulic pressure at the
auxiliary pump test port within
specs?
Check the auxiliary pump,
compressor motor and related
hydraulics.
Check the compressor and air
conditioning system components.
No Yes

FORM NO. 56043123 - SR 1900 - 17
COMPONENT TROUBLESHOOTING
Compressor Motor Hydraulic Valve (L10)
Refer to Figure 5-1.
Note: The Compressor Motor Hydraulic Valve and Hydraulic Pressure Test Port are attached to the tee-fitting off of the Accessory Hydraulic Pump.
Disconnect the1. Electrical Connector from the Hydraulic Valve.
Switch on the A/C and check for 12 VDC at the2. Electrical Connector.
Check the coil resistance of the3. Hydraulic Valve. It should be approximately 7±20%.
If there is 12 VDC at the4. Electrical Connector and the coil resistance is within spec, disassemble the Hydraulic Valve and clean or replace the cartridge as
necessary.
FIGURE 5-1 – Compressor Motor Hydraulic Valve
Hydraulic
Pressure
Test Port
Accessory
Hydraulic
Pump
Electrical
Connector
Hydraulic
Valve (L10)
Accessory (Gear) Hydraulic Pump
Refer to Figure 5-1.
Connect a hydraulic pressure gauge to the1. Hydraulic Pressure Test Port off of the Accessory Hydraulic Pump.
Start the engine, then switch the A/C on and off at the two engine speeds and note the hydraulic pressures at the2. Hydraulic Pressure Test Port. The
following chart shows pressure values that are representative of what you should be reading at normal operating temperature if the Accessory Hydraulic
Pump, Hydraulic Valve and compressor motor are working correctly. Note that pressures tend to be higher if the hydraulic system is below normal
operating temperature.
Hydraulic Pressure at Test Port
(typical)
Difference in Hydraulic Pressure
between A/C off and A/C on
Engine at idle, A/C off 500 psi
380 psi
Engine at idle, A/C on 880 psi
Engine at high speed, A/C off 675 psi
425 psi
Engine at high speed, A/C on 1100 psi
If you don’t observe differences in the hydraulic pressures similar to those in the above chart when switching the A/C on and off, it could indicate a problem with
the Hydraulic Valve (L10), the Accessory Hydraulic Pump or the A/C compressor motor.

18 - FORM NO. 56043123 - SR 1900
COMPRESSOR RELAY (K10)
Refer to Figure 5-2.
Note: The Compressor Relay is located in the engine compartment below the main broom lever.
Make sure the hopper is down, then switch on the A/C.1.
Back-probe the BLU/BRN wire connected to the2. Compressor Relay.
If you see 12 VDC at the BLU/BRN wire referenced to battery negative, the Compressor Relay is working correctly.
If you don’t see 12 VDC at the BLU/BRN wire, proceed to step 3below.
Remove the electrical connector from the3. Compressor Relay and check for continuity across the load terminals (30 and 87a).
Note: The Compressor Relay is a normally-closed relay and should have continuity across the load terminals with the electrical connector removed.
If there is continuity across load terminals 30 and 87a, the Compressor Relay is working correctly. Check the connections and wiring upstream of the
Compressor Relay and repair/replace as necessary.
If there is very high resistance or no continuity across terminals 30 and 87a, replace the Compressor Relay.
FIGURE 5-2 – Compressor Relay
Compressor
Relay (K10)