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HVAC vent door problem

A

Acesneights1

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Can't figure out what's going on. The thing works ok when you first get in it but then I lose the abilty to change from floor to vent and I hear the trap door for recirc opening and closing byitself and no real strong air coming from any one place. I thought it was the control head so I replaced it with brand new ac/delco from Advance and it seemed ok for a few days but now it's doing it again ? Why the hell they ever stopped using cables I have no idea. Chinese made PCB crap.
Bad new Control head ?
Something else ?
 
Have you checked the ground behind the glove box? I had the same issues and it ended up being a bad ground connection for the blower feed.
 
Grounds were perfect. There is a wire form the ecm that is cut but it has been that way since i have owned the truck. I guess I'll try replacing the acutator next. God I hate electronics. My 86 doesn't have any of these problems.
 
I read the thread(good BTW) but I don't think that is my problem. I can get the other vents to work in the am when truck is first started up then as it gets hot or time passes it goes ballistic. Seems to happen if I put the fan to low . I am thinking actuator motor at this point. Before this started happening it would hang up switching to a/c vents and a well placed kick to the actuator motor solved the problem....
 
Is there more than one actuator ? I see air door then hvac blend door. What junk. my 93 has a different setup and it works flawlessly. I have owned a bunch of these truck and not friggin one of them ever worked right.
 
I figured I'd return the ac control head since it's under warranty from Advance...They no longer carry it...the plot thickens. When they stop carrying something it's either lack of sales(which I doubt since these go bad all the time)or the quality of the part...Guess I'm going to the junky . WTF...Do I have a 1930's something that I gotta scrounge Junkyards for parts...
 
You have checked for a melted connector that feeds the HVAC unit behind the glove box? Low voltage will cause a mess...

When the recurc door closes see if you can push it by hand. If so the actuator is bad.
 
WarWagon said:
You have checked for a melted connector that feeds the HVAC unit behind the glove box? Low voltage will cause a mess...

When the recurc door closes see if you can push it by hand. If so the actuator is bad.
Click to expand...

It's literally going ballistic. The recirc door is opening and closing, the vents are all messed up lie I hear the blower going like mad but air is not coming out anywhere. Then After I shut the truck off for a bit and turn it back on everything is normal again.
 
The 2 wire plug behind the glove box with the red and black wires in it, did you unplug this one and check it? Mine looked fine with no signs of distortion, but as soon as I unplugged it I could see the poor connection. The control head has it's own ground, but all of the motors are grounded off of the blower motors ground. i had all kinds of problems with mine until I cleaned the connections in the plug and added in an extra ground wire. Now no more problems with nearly instant door changes.
 
Well, I put another new Control head in(warranty replacement) and it made no difference. I ma beginning to think it's freezing up. I noticed the Cycle switch is Made in China junk so I'm gonna get one from GM today. Had this problem with my 93 a few weeks ago except it was not affecting the operation of the doors. A used GM cyle switch from the junky fixed it. I made more observations. After the truck sits the doors work fine(the vent is a bit sluggish but works) After cruising for about 15-20 mins with the A/C fan on low and air door on recirc it all of a sudden goes nuts. Air doesn't really seem to be coming out of anywhere but fan is blowing and the recirc door starts opening and closing by itself. If I kick it off Recirc the recirc door stays open but still getting no air from any particular vent. So I tried a little experiement as I pulled into the parking lot. Put the bitch on full blast heat. After a few minutes, the vent/heat door switched..Hmmmmmm....Possibly getting so cold in the box making everything go screwy ? I don't know how these electronically controlled crap unit work(God I miss cables)but something IMHO is freezing and the only thing that can cause freezing is a bad switch. It's not cycling and the Compressor is running too much. Will replace the switch hopefully today. I want a GM one, no more auto part chinese made garabge. I peronally don't like these systems anyway. The older expansion valve systems were way less trouble some and could work in the most grueling conditions.

This is exactly why when i did pro a/c I would not work on cars. Give me a Mack or KW/Pete anyday...:D
 
Kenny that's one thing i love about the K-5s system. It's not electronic. It's vacuum. Not a bad system, but slow with the vacuum pump, at least until i did my modification by adding in a vac storage tank from a gasser into the A/C vacuum supply.

The only cable is the blend door. Vent selection and A/C recirc is vac. My 96 is all cables.
 
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