Compressor Clutch Control Diagnosis - Electronic Touch Climate Control

Fig. 3 Blower control pin identification (Typical):

Perform diagnosis procedure if clutch fails to engage when ambient temperature is above 50-55°F. Prior to performing diagnosis, check to see that compressor clutch diode is not shorted. Diagnosis must be performed with engine running, temperature and mode LEDs lit, and mode set to "A/C," "BI-LEVEL," or "DEFROST."
1. Connect voltmeter between compressor clutch output (pin 5), Fig. 3, and ground:
a. If 8-12 volts is indicated, check for defective clutch, pressure switch or ground. If a poor ground exists, proceed to step. 4.
b. If 0 volts is indicated, proceed to step 2.
2. Connect voltmeter between ignition terminal (pin 3) and ground:
a. If 8-12 volts is indicated, proceed to step. 3.
b. If less than 8 volts is indicated, check for short or open in ignition wire between blower/clutch control and control panel. Correct as necessary.
3. Connect voltmeter between clutch control input (pin 4) and ground:
a. If 4-6 volts is indicated, proceed to step 4.
b. If 10 volts or more is indicated, proceed to step 5.
c. If 3 volts or less is indicated, proceed to step 6.
4. Connect suitable jumper wire between compressor clutch output (pin 5) and A/C compressor clutch:
a. If clutch engages, check for low Freon charge, inoperative pressure switch, or other control device stopping operation. Recharge system, replace pressure switch or repair as necessary.
b. If clutch does not engage, replace blower/clutch control assembly.
5. Connector voltmeter between pin C of control panel 8-way connector and ground:
a. If 10 volts or more is indicated, replace control head.
b. If less than 10 volts is indicated, repair open in circuit between pin C on control head and clutch control input (pin 4).
6. Check continuity of circuit between pin C on control head and clutch control input (pin 4):
a. If circuit is shorted to ground or open, replace wire.
b. If circuit is satisfactory, replace control head.