Silver79

I recently started sorting out some of my HVAC issues on my 87 and have the infamous full cold or full heat symptom. Both interior and exterior sensors are connected and seem to read the appropriate resistance value associated with temperature. When I disconnect the connector from the setting motor and measure resistance across pins 4 and 12 I receive a reading of 5.7 Kohms, which is out of spec. When I move the temperature slider the resistance does not change. I am starting to think that the control head has an issue in the temperature circuit. Any other thoughts?

GlenL

Do you have the automatic head or the manual head?

Have you checked the sensor measurements at the sensor or at the head?

ROG100

On your 87 it will be an automatic head unit 09R.

Silver79

Automatic hvac as Roger said. I checked the resistances of each sensor at the sensor connectors. The 5.7 Kohm reading was read at the setting motor connector pins 4 and 12. Suppose I'll check the resistance values at the head.

Silver79

Finally got around to checking some resistance measurements at the control head and received some weird readings. Removed the pins from the wiring harness side of the exterior temperature connector and found both of them to be connected by literally 1 strand of wire. Installed new pins and now everything works as it should. Thank you for the help.