AC / Heater stuck in hot temp control and high fan

[Plumber101010]

Update: So whatever the issue was it was related to something that had to do with the wiring going haywire! 

 

My Alpine stereo was also having issues not turning off when I turned off the ignition (that’s why the batteries were going dead and I didn’t want to bring it up) but it finally also completely died and I could get no power going to it!

 

So I brought it to the car stereo place and was lucky to find one LAST unit left at Crutchfield that’s a GM restyling 10 inch touch display which I absolutely adore!!! Fantastic system.

 

Any who, all I know is when I went to pick it up, and I never mentioned (on purpose in hopes I could claim they damaged something LOL) anything about the heater and AC not working and being stuck in the hot / fan blowing position, everything was working absolutely perfectly!!!! 

 

Killed two birds with one stone on that one and consider myself very lucky!!!! 

[Doug_Scott]

It was most likely a bad ground connection that also impacted your head unit.   You would be amazed at what a bad ground connection can do   I did a predelivery inspection on a brand new 1977 Chrysler New Yorker that was shipped with the master ground connection not attached to anything.  It's been far too long to recall what one nut missing did, but one was pressing in the cigarette lighter would illuminate the dome light, and another one was applying the parking brake would turn on the door ajar light.  There were 5 or 6 bizarre behaviours that did not seem to have any common causes.  I ended up having to remove the entire dash in order to locate the master ground location.  I found the post installed on the firewall, with the nut loosely wound on about 10 full turns, but not a single wire. I felt the harness about a foot in either direction and found an oddly shaped item in the one direction.  After unwrapping about a foot of harness I found a daisy wheel of ground wires with a hole in the centre.  Connected it up to the single stud on the interior side of the firewall, put the dash back together and found it fixed all the seemingly unconnected issues.  Back then Chrysler paid straight time for wiring repairs which was a good thing given the number of hours I spent on that car. That one car made me always go straight to ground connections first and make sure they are good first.