Rear Heat/Air Problems

[03Z71Tahoe]

Hello, and I want to thank everybody for any help in advance.
I have 2003 Tahoe and recently I had a dead battery after letting the truck sit for a period of hours. After getting it running again, I notice noise coming from the back of the truck, and after a little investigating, noticed that there was air blowing out of the rear vents.
Of course the first thing I checked was both the front and the read controls and they were both off, but it was still blowing air (sound like it was on high). If I use the controls to adjust the amount of air (high/low) it will change that setting, but the blower will NOT turn off.
If I turn the truck off, I do not notice that the air is still running/blowing, but yet if the truck sits for more then a few hours, the battery is dead again.
At this point, I pulled the rear HVAC fuses (I pulled two fuses, one from the fuse pane inside the truck and one from the panel under the hood) and the air stops blowing and the dead battery problems go away. This leads me to believe that there is something on that rear air system that is running or trying to run while the truck is off.

I do feel that by pulling the fuses on the rear system and the problem going away, that I have isolated the problem to the rear HVAC.
I did take this to the local dealer, but needless to say all they could tell me was that after searching their "forums" they "THINK" it is the heater/blower control module. They did quote me a price, but to pay $400 on something that they "THINK" might fix the problem, I just could not justify that on an assumption.

So, at this point I am looking for answers on my own. I am not sure what it takes to replace this heater/blower control module, or if this is even the problem, but would like to get the problem fixed. In the mean time, I have just pulled the fuses to stop the battery drain problem.

I will also mention that the rear heat has never worked, it will blow air, just never got hot, or even warm for that matter. Not sure if this is related, but thought I would throw it out there. And maybe this part will fix both problems, but at this time I am more interested in getting the dead battery problem resolved.

Has anybody ever heard of this before, or possible know what might cause this?
Then, if it is the heater/blower control module, is this something that is not too difficult to replace? Something that maybe I could try myself?

Any advice or help would be greatly appreciated.

Thanks again.
Chris

 

[Holikz]

Sounds like it an electrical problem, check your wire harness with a volt meter for the rear a/c and try to find where the current is passing through...the control module could be damage...hope this helps.

my hoe has a similar problem, mine just won't start the rear a/c which I found to be an electrical problem..

 

[Fishtoez]

Chris, I just recently experienced the same problem, or very similar. I posted about it, also asking for help but not sure about the quality of detailed responses. Unfortunatley, I see a whole lot of posts from people on this site but not a lot of detailed resolutions being offered up. Anyway, I'm getting the sense that we have a problem with the control module but I'm still researching. See my post dated 5 March.

 

[xjnash]

I just started to have the same problem. I woke up one am and battery was dead. When we are at a light and the ac kicks on I see the volt gauge drop to 14 and the motor seems to want to die. This has happen before but I cleaned the Mass air sensor and it went away. Well now it really noticeable and back.

I thought it was the Alternator but after going to wal-mart tonight I notice the rear air staying on. I asked my wife why the hell the rear air was staying on after the key was off. Her response was it does that but cuts off in a few. well after shopping etc came back and it was still on.

So I think I have found the reason for the dead battery. Also to note that recently the rear air only has been switching or plusing hi lo hi low then stops for no reason.