Improper Temperature Control
Fig. 8 Adjusting Terminal Location.:
NOTE: Refer to WIRING DIAGRAMS for correct terminal identification.
1. Start engine and allow it to reach operating temperature.
2. Place blower switch in "AUTO" position.
3. Disconnect "check" connector from its normal connection, and connect it to the "check" connector of the amplifier, Fig. 7, then check that power servo stem moves smoothly by sliding the temperature control lever. If servo stem does not move, check vacuum in vacuum motor of power servo. If there are more than 12 inches of vacuum in "Max" Hot position and no vacuum in "Max" Cool position, replace power servo. If not, proceed to next step.
4. Check voltage at power servo between terminals 9 and 10 when sliding temperature lever to "Max" Cool, and between terminals 9 and 11 when sliding temperature lever to "Max" Hot. If there is no voltage, proceed to step 5. If there is voltage, check DVV. If DVV is defective, replace it. If DVV is OK, check and repair vacuum circuit.
5. Check voltage at terminals 5 and 1 of amplifier. If voltage is present, proceed to step 6. If there is no voltage, check voltage at terminal 5 of amplifier and ground. If voltage is present, check and repair open circuit in wire from terminal 1 of amplifier to ground,. If there is no voltage, check and repair open circuit in wire from terminal 5 of amplifier to battery.
6. Check resistance of rheostat between terminal 1 and 2. Resistance should be more than 2450 ohms at "Max" Cool and less than 550 ohms at "Max" Heat. If resistance is as specified, replace amplifier. If resistance is not within specification, check and repair rheostat wire, or if necessary, the rheostat.
7. Check resistance between terminal 2 of in-car sensor and terminal 9 of amplifier. If resistance is not 1500-7500 ohms, proceed to step 8. If resistance is not as specified, check in-car sensor resistance. If resistance is not 1000-6000 ohms, replace sensor. If resistance is as specified, check ambient sensor resistance. If resistance is not 500 to 1500 ohms, replace sensor. If resistance is as specified, check and repair open circuit in wiring to sensor.
8. Set temperature control lever at 77 and check that white line on power servo stem is within orange range. If it is, proceed to step 9. If white line is not within orange range, proceed as follows:
a. Exchange connection of adjusting terminal. Refer to Fig. 8.
b. If white line is within the orange area, proceed to step 8. If white line is not within the orange area, check resistance of rheostat at terminal 2 and adjusting terminal. Resistance should be 1450-1550 ohms.
c. If resistance of rheostat is not within specifications, replace rheostat.
d. If resistance of rheostat is within specifications, check resistance between terminals 1 and 7 at power servo. With stem fully extended, resistance should be 1700-1900 ohms, and with stem fully retracted, resistance should be 150-250 ohms. If resistance is as specified, proceed to step 9, if not, replace servo.
9. Check air mix damper operation. If operating properly, proceed to step 10. If not, make the necessary repair on damper links.
10. Slide temperature control lever completely to the right towards "Max" Hot and check for hot air. If cold air comes out, proceed to step 11. If hot air comes out, push A/C switch to "On" position and check for cold air coming out when temperature lever is moved completely to the left towards "Max" cooling. If cold air comes out, the system is operating normally. If warm air comes out, check and repair problem in refrigerant system.
11. Check water valve. If it is open, check and repair heating portion of system. If water valve is closed, check for vacuum at the valve. If vacuum is present, replace valve. If there is no vacuum, check vacuum circuit. If vacuum circuit is OK, proceed to step 12. If vacuum circuit is not OK, make the necessary checks and repairs.
12. Check voltage at terminals 8 and 9 of power servo. If there is voltage, replace power servo. If there is no voltage, check for voltage between terminal 9 and vehicle ground. If there is no voltage, repair open circuit in wire between terminal 9 and battery. If voltage is present, repair open circuit in wire between terminal 8 and ground.