Section 50 - Climate Control - Chapter 1
50-1-65
Standard Controller Test
The following tests determine whether the A/C
controller requires replacement, since it tests primary
input and output circuits. Some test steps isolate
system problems to specific circuits which can
simplify general troubleshooting.
In general, the service technician should resist the
temptation to replace the controller as the solution to
all A/C system problems. Double check your test
results to avoid a return service call. The absence of
key control voltages or switched ground does require
controller replacement.
NOTE: The following tests are performed with both connectors installed on the controller using an appropriate
service probe and digital voltmeter.
* The standard controller and many components are grounded to “HVAC ground.” HVAC ground is both a grounding stud at the
rear of the HVAC box and chassis ground at ring terminal 172F through C139-F on wire 178-Bk.
Test
Number
Pin ID
Description
Wire/
Color Test Points
6-Pin
Conn
2A--> Controller Power (+) 252-Or Pin A to Battery GND
7B--> Evaporator Temp Sensor PB-S Pin B to Battery GND
5C--> High Pressure Switch 80-Or Pin C to Battery GND
9D--> Temperature Control Pot 103-Or Pin D to Battery GND
11 E --> A/C On/Off Switch 112-Or Pin E to Battery GND
1F--> Controller Ground (-) MOD-Bk Pin F (6-pin) to HVAC ground
5-Pin
Conn Description
Wire/
Color Test Points
8A--> Comp Clutch Relay 1A-Or Pin A (5-pin) to chassis ground
6B--> Low Pressure Switch LP-Or Pin B (5-pin) to Battery GND
10 C --> Pressure Warning Lamp 111-Or Pin C (5-pin) to Battery GND
4D--> Heater Cont Valve Sig 9C-Or Pin D (5-pin) to Battery GND
3E--> (+) Heater Cont Valve Pwr 6D-Bk Pin E (5-pin) to Battery GND
*HVAC GROUND
CHASSIS GROUND
BATTERY GND - Battery Negative Post (-)
Test Instructions and Actions
Test ground continuity to controller: Pin F (6-pin) to HVAC ground
Condition(s): A/C Switch OFF
Expected Result: Less than 1 ohm
Action: Restore clean ground and retry the unit.
Confirm switched B+ is present at controller: Pin A to Battery GND
Condition(s): Keyswitch ON
Expected Result: 12V
Action: Restore 12V and retry the unit. See Controller Power and Ground, page 86, in this Chapter.
1
2
To Next Page
Loading...
Need help?
General
