2004 Chevy Diesel Dual Heater Control Problem - PROBLEM SOLVED

[chasdvorak]

I had a problem with my Chevy heater control a few years ago and should have posted my solution since I received a couple of inquiries regarding the same problem. The thread is currently closed due to its age so I thought I'd repost a discussion that was developed through the forum. I've listed an email exchange below that I had with Todd McDaniel regarding this problem and it explains our fixes. I'm hoping this helps explain the problem and saves some time and $$$$.


On May 12, 2014, at 8:27 AM, Chuck Dvorak wrote:

Good Morning Todd,

So here's what I learned....kinda the hard way. Some of the older Chevy's have this problem and it is tied into the auto temperature thermostat. When the system fails.....it gives you a choice between hot or cold and no in between which you are experiencing now. The first thing I tried was to install a rebuilt temperature control. I found a guy from Tennessee, I think, on eBay who rebuilds the temperature panel. If I recall properly, he even had links which showed how to take the dashboard apart. It sounds like a lot of work, but it was pretty easy.

Unfortunately, that did not work and I pitched $75 or so into the wind since I had the same problem. Then I took it to the Chevy dealer located within 300 yards from my home. They took me for a ride to the tune of about $400 which was mainly labor. Here's what they found....there is a small thermostat which is located in the headliner of my truck right above the driver. It is a round plastic thing with several small holes in it. Apparently this monitor the temperature inside the truck and adjusts it accordingly when you set the heater/ AC to the auto mode. They told me it was tricky to locate the problem since the wiring which connects the heater to the thermostat was broken and it had to be replaced. They socked me with 3 hours of labor to locate the problem and then blamed it on my brake controller wiring...which was total crap since the brake wiring wasn't even close to heater panel.

I was aware of the possibility that the thermostat might be faulty and I tried to check it with a volt/ohm meter. I was able to pry the unit from the headliner but I didn't get any voltage reading which may or may not be an indication of a faulty wiring harness. I think the advice I received before going to the dealer was that the voltage was very low and it might not show on the meter.....still something to check to possibly rule out the wiring harness if you do find voltage.

So....the options are to try and troubleshoot it yourself or take it to the dealer. The guy on eBay was decent and the turnaround time was pretty quick, but in my case the panel was good. I'm not sure if a regular mechanic could troubleshoot it cheaper than a dealer. That said, the Chevy dealer I used were a bunch of crooks. They opened shortly before the financial crash and closed within a year or two. I asked them to show me the book price for the repair and they said it didn't apply since it required several hours of "diagnostics". I even tried to ***** to GM corporate but in the end I had to pay. If you have a Chevy dealer you trust it might be worth a phone call to see if they offer a guesstimate. I picked this dealer because they were close, had appointments available and it was really cold at that time of the year. I really should have taken the truck to a dealer I trusted.....lesson learned.

Good luck with your fix. I'd be curious to hear how you resolve this issue but give me a call if you have any further questions.

Take care,

Chuck Dvorak



​

Chuck that part in headliner is called some kind of asperator cost me 70 bucks but it did the trick my dealership said they have never had to replace one was so glad I seen ur post it saved me a lot of money. Thanks a bunch.


Todd

Sent from my iPhone





Safe Travels,

Chuck Dvorak

 

[chrissands]

....there is a small thermostat which is located in the headliner of my truck right above the driver. It is a round plastic thing with several small holes in it. Apparently this monitor the temperature inside the truck and adjusts it accordingly when you set the heater/ AC to the auto mode. They told me it was tricky to locate the problem since the wiring which connects the heater to the thermostat was broken and it had to be replaced.

That little round doo-hickey above the driver's head is called an "aspirator". It has a little fan in it that draws cabin air across a temp sensor, which sends a signal to the control panel to adjust the temp and airflow as needed to maintain the set temperature

GM trucks that have the climate control (where you dial in a temperature on the controls) have it - which is just about all trucks these days, except a stripped down "work truck"

 

[TravelTiger]

That little round doo-hickey above the driver's head is called an "aspirator". It has a little fan in it that draws cabin air across a temp sensor, which sends a signal to the control panel to adjust the temp and airflow as needed to maintain the set temperature

GM trucks that have the climate control (where you dial in a temperature on the controls) have it - which is just about all trucks these days, except a stripped down "work truck"

Our aspirator "buzzes" sometimes after we hit a pot hole or similar rough roads. If you push on it, it stops. Not sure what this could be.


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[Bob&Patty]

Erika, the buzzing is the fan motor because of dirt buildup on the fan blades. Yes it is called an aspirator and they do not go bad that often. You can't get a voltage reading because it uses OHM's resistance to work. You can test its operation at the A/C control head with a volt/OHM meter {Fluke). If your A/C blows hot all the time... try using a heat gun aimed at the aspirtor to see if it changes to cold. Sounds to me like the tech at the Chevy store did not know how to use the GM scan tool. The scan tool will tell you everything you need to know about the HAVC system and what is wrong. These systems set fault codes, which in turn tells you what componet has failed. Quick, simple and easy. The most failed parts are the temp door actuators. They will stick and cause one or both sides to blow the wrong temps. Those are very easy to diagose with the scan tool. How they work is a looong story.

 

[TravelTiger]

Erika, the buzzing is the fan motor because of dirt buildup on the fan blades. Yes it is called an aspirator and they do not go bad that often. You can't get a voltage reading because it uses OHM's resistance to work. You can test its operation at the A/C control head with a volt/OHM meter {Fluke). If your A/C blows hot all the time... try using a heat gun aimed at the aspirtor to see if it changes to cold. Sounds to me like the tech at the Chevy store did not know how to use the GM scan tool. The scan tool will tell you everything you need to know about the HAVC system and what is wrong. These systems set fault codes, which in turn tells you what componet has failed. Quick, simple and easy. The most failed parts are the temp door actuators. They will stick and cause one or both sides to blow the wrong temps. Those are very easy to diagose with the scan tool. How they work is a looong story.

Thanks for the info, We have not had this "looked at" by anyone. The hot-air when it should be cold, or cold-air when it should be hot, happens pretty rarely rarely, so haven't wanted to incur the expense.

 

[Hemi392]

This is very interesting because I own a 2004 Silverado 3500 and it does the same thing. Intermittently blows hot air on the drivers side when the ac is on. Sounds like I finally have an answer to this issue. Thanks!


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[jimtoo]

This is very interesting because I own a 2004 Silverado 3500 and it does the same thing. Intermittently blows hot air on the drivers side when the ac is on. Sounds like I finally have an answer to this issue. Thanks!


Sent from my awesome red hot smokin iPad mini!

I also have an 04 GMC 3500 and it does the same thing every once in a while. I just stop, turn it off for a minute, start it back up and 99% of the time it opens the door and cools like it's supposed to.

Jim M