Control Module HVAC: Adjustments

Note: Always check air temperature sensors before checking programmer calibration.







If programmer is out of calibration system may run slightly cooler or warmer than temperature selected on control head.


- Disconnect wires from evaporator air temperature sensor
- Using digital ohmmeter set resistance of VW 1301 to 113 ohm (roughly equal to scale number 208).





Four point test plug

- Connect VW 1301 to terminals S and A on 4 point test plug (wires are blue and blue/white).
- Connect digital voltmeter US 1119 to terminals W and N on 4 point test plug (red/green and brown wires).
- Set control head to Auto 75°F (24°C).
- Turn ignition "ON".
- Wait 2 minutes.
- Read voltage. Should read 3.95 to 4.0 volts. If voltage reading is not correct, continue.
- Insert small screwdriver into opening of programmer (arrow).
- Turn potentiometer until voltmeter reads 3.95 to 4.0 volts.


Note: An error of 0.2 volts means temp variation of 1° (.56°C). If voltage is under 3.95 volts, system runs too cool. If voltage is over 4.0 volts, system runs too warm.






Adapter can be made locally to check/adjust programmer calibration.