Hvac

[big61fourby]

A/C is giving me fits...Here's the diagnosis:

Compressor clutch can't make up it's mind, locked unlocked; very sporadic. Bypass both high and low pressure switch, same symptoms. Check freon pressure, all good. Jumper across relay, and the clutch work perfect, swap with starter relay, same symptoms. Clutch only engages whenever juice is supplied, so the clutch is working right. That leads me to believe that whatever controls the A/C relay (underhood fuse center) is misbehaving. So,

1) I'm beginning to suspect the HVAC control unit in the dash. I pulled the whole thing apart, and nothing looked amiss. Need to poke around with a test light, but is it possible for the 'A/C' switch to go flakey?

2) My Hayes manual (yeah, i know...) shows the relay getting signal from the "vehicle control module", which is different from the HVAC control unit in the dash. What the heck is that?

What am I missing?

[moondoggie]

Good Day!

Since nobody that actually knows anything answered...

Yeah, it can be the in-dash HVAC unit. I have NO IDEA how to check this out. Have you got a friendly boneyard handy? They might let you buy one & allow you to return it if it doesn't fix your problem, or at the very least try one on your truck right there in their parking lot. (It's pretty easy to have your dash apart enough to allow a very quick swap-&-try.)

Good Luck & Blessings!

[big61fourby]

At this point, I'm leaning more towards the dash unit being faulty. Tore the whole thing completely apart yesterday, fiddeled with the switch for a while, slammed it back together, and it worked the entire 100 miles to work and back today. So it seems to be either the unit, or one of the connections on the back that I unplugged during disassembly. Think I might run it for a while and see if the problem reappears before I start shopping.

Anybody with '96 + manuals--Does the dash unit control the A/C relay, or is there something else in-line????

Come to think of it, a buddy of mine does have a '98 Z71, and he is gone for the week...;)