2002 Avalanche HVAC problem

[blazinjamm]

I have a 2002 Avalanche with Auto Climate Control. This summer my A/C would work sometimes and sometimes it wouldnt. I tried fixing it, but gave up due to frustration. Well, winter is here and even though I dont mind the lack of heat, I do mind the lack of a defroster. Everything works fine, but I cant get the blower to kick on. Going by previous help I have replaced the blower, the blower control module and the hvac control module. Nothing has changed. When I adjust knobs, I hear all the little doors opening and closing, but no blower. When this first happened the a/c would work for a day, then stop for 2 days, then work for 3 hours, then I turn the key off and it wouldnt work when I started it again. I have tested pretty much everything and I have come up with 1 major problem. From the hvac controller there is a black/gry wire, it sends a variable signal to the blower control module. Everyplace I have looked and everyone I have talked to tells me this blk/gry wire is variable 0-4volts positive. No matter how I test it, it always comes back variable 0-12volts negative. Can someone please help? Im tired of tracing wires in my dash, and I want to go play in the snow. Thanks

[MT-2500]

Best to get it on a good HAVC/ body capable scanner and get codes and see what is going on.
Post back any code no that you may have.
Some of them use a modjulated voltage control that can be only checked on a lab scope or a high end volt/ohm/meter.

For testing and repair flow charts go fpr a factory repair manual or a all data sub.http://www.alldata.com/products/diy/index.html
MT

[Unknown_USER]

I had exactly the same problem this past summer after 2 years of no heat/air conditioning.

I took it in since the cat got clogged and had them fix both issues. Turned out that there was some melted wires that hook up to the fuseblock in the dash on the driverside. They replaced it and it works again.

[HUNTERPAUL]

Originally Posted by blazinjamm

I have a 2002 Avalanche with Auto Climate Control. This summer my A/C would work sometimes and sometimes it wouldnt. I tried fixing it, but gave up due to frustration. Well, winter is here and even though I dont mind the lack of heat, I do mind the lack of a defroster. Everything works fine, but I cant get the blower to kick on. Going by previous help I have replaced the blower, the blower control module and the hvac control module. Nothing has changed. When I adjust knobs, I hear all the little doors opening and closing, but no blower. When this first happened the a/c would work for a day, then stop for 2 days, then work for 3 hours, then I turn the key off and it wouldnt work when I started it again. I have tested pretty much everything and I have come up with 1 major problem. From the hvac controller there is a black/gry wire, it sends a variable signal to the blower control module. Everyplace I have looked and everyone I have talked to tells me this blk/gry wire is variable 0-4volts positive. No matter how I test it, it always comes back variable 0-12volts negative. Can someone please help? Im tired of tracing wires in my dash, and I want to go play in the snow. Thanks

If the problem is with the blower not working the blower resistor is a common failure due to a blower motor drawing to many amps. Usually when this fails the blower will work on high only then fail completely.

[Fireman7606]

Not sure if this will help but try and pull the hvac fuse under the hood for a min and then put it back in, that should do a rest on the comp, like i said it might not help but wouldnt hurt to try