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2004 HVAC Issues - Getting Really Burnt Out!

Brewtal66

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Brewtal66 Enthusiast

Brewtal66

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Hey Gang,

The wife has a 2004 Suburban we bought about 7 months ago. This thing has been nothing but problems since and I'm really at my wits end with it. Ready to sell it and get something else. 

 

Her car has the digital automatic temp controller.

How it all started is we were coming home from Thanksgiving and the front windshield started to fog up. I noticed that when I put set the defrost setting, no air was coming out. After some researching I figured out that the HVAC actuators are prone to going out on these.

I found the one that controls these vents which is by the gas pedal. Replaced it, and no difference. A quick google search again reveals I need to calibrate the computer to the new actuator. I also replaced the actuator on the bottom of the unit. 

Here's where it gets a little fuzzy. I've done this relearn procedure and a another one probably a dozen times. The end result is usually one of two outcomes:

1. The heat works in the front and the rear, but no A/C. The A/C light will actually blink three times but that's it. 

2. AC works, but no heat. The rear AC blows ice cold, even when on the heat setting. 

Mind you before I started messing with all this, the heat and AC worked pretty normal for the most part. 

Now when in Scenario 1 where the heat works but only getting the blinking light. Another google search revealed that the air temp sensor by the passenger side turn signal needs to be replaced. I replaced that, but nothing changed(even after a few re-calibrations). 

 

Two other things to mention: In scenario 1 if I set it at 90 degrees, it blows hot air like it should. If I set it to 60 degrees, it still blows hot air. The other thing that's now happened is when driving over 55MPH on the interstate, I have a pretty loud whistle from the passenger side dash. Doing different settings on the heat/AC doesn't change it. The whistle gets louder the faster you go. 

Any ideas? I'm really at my wits end here with this damn car. Thanks for all the help!

swathdiver Senior Enthusiast

swathdiver

Posted
Posted

You're wasting time and money Tim.  You need to get the internal BCM codes that will tell you what's going on.  You can buy a Tech2 for about $300 and see the codes and do the relearn properly or find someone who has one or another bi-directional scan tool that can read BCM codes.

 

There are 4 actuators up front and 2 or 3 ways that each can fail.  The trouble code would be followed by a symptom number.  Then again, it could be the module and if your rear AC is acting up, there are two actuators back there as well.

Brewtal66 Enthusiast

Brewtal66

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3 hours ago, swathdiver said:

You're wasting time and money Tim.  You need to get the internal BCM codes that will tell you what's going on.  You can buy a Tech2 for about $300 and see the codes and do the relearn properly or find someone who has one or another bi-directional scan tool that can read BCM codes.

 

There are 4 actuators up front and 2 or 3 ways that each can fail.  The trouble code would be followed by a symptom number.  Then again, it could be the module and if your rear AC is acting up, there are two actuators back there as well.

Thanks James. I'm pretty mechanical, but how hard are the Tech2 tools to use? What other things can they do? I don't mind investing in tools, but want to make sure I can get my monies worth with them. 

 

The rear AC and Heat were working perfect before I did the re-calibration, so I think those actuators are working okay. 

Brewtal66 Enthusiast

Brewtal66

Posted
  • Author
Posted
3 hours ago, swathdiver said:

You're wasting time and money Tim.  You need to get the internal BCM codes that will tell you what's going on.  You can buy a Tech2 for about $300 and see the codes and do the relearn properly or find someone who has one or another bi-directional scan tool that can read BCM codes.

 

There are 4 actuators up front and 2 or 3 ways that each can fail.  The trouble code would be followed by a symptom number.  Then again, it could be the module and if your rear AC is acting up, there are two actuators back there as well.

Also, do you have a link to one of those scanners? I'm looking at them but seems like there are copy cat ones that don't actually work. 

swathdiver Senior Enthusiast

swathdiver

Posted
Posted
57 minutes ago, Brewtal66 said:

Thanks James. I'm pretty mechanical, but how hard are the Tech2 tools to use? What other things can they do? I don't mind investing in tools, but want to make sure I can get my monies worth with them. 

 

The rear AC and Heat were working perfect before I did the re-calibration, so I think those actuators are working okay. 

A Tech2 is the tool GM techs use to work on and fix these cars.  It was replaced after 2013 by a different system which uses a laptop.  There is a learning curve, it can do more than I've probably discovered.  One neat thing is graphing and recording data while on a drive such as looking at O2 sensors or looking for misfires or knock retard.  It's also the tool used to bleed ABS brakes.

 

If I hooked mine up to your truck, I would command each actuator into position and note how many counts off it was from the commanded state.  It can also properly recalibrate them.  That's just the tip of the iceberg as to what these can do.  Well, the very first thing would be to scan the whole truck for trouble codes!

 

Since GM went on to something else, the factory in China keeps making them, they are not clones, but actual Tech2s that are no different from the ones sold by Vetronix.  Over the years different companies were licensed to produce and sell them.  OTC and Bosch used to as well.

 

Mine came from China last year.  So far so good.  Got the case and made sure it had the last software update, 33.004 for the PCMCIA card.  Bought off Aliexpress and arrived in half the time quoted via DHL.

 

Don't know of a current link, I would check the forums for the latest posts from folks who recently bought them and also look for vendors who have good feedback.  Many guys bought them this year over at the TahoeYukon forum.

 

 

Brewtal66 Enthusiast

Brewtal66

Posted
  • Author
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15 hours ago, swathdiver said:

A Tech2 is the tool GM techs use to work on and fix these cars.  It was replaced after 2013 by a different system which uses a laptop.  There is a learning curve, it can do more than I've probably discovered.  One neat thing is graphing and recording data while on a drive such as looking at O2 sensors or looking for misfires or knock retard.  It's also the tool used to bleed ABS brakes.

 

If I hooked mine up to your truck, I would command each actuator into position and note how many counts off it was from the commanded state.  It can also properly recalibrate them.  That's just the tip of the iceberg as to what these can do.  Well, the very first thing would be to scan the whole truck for trouble codes!

 

Since GM went on to something else, the factory in China keeps making them, they are not clones, but actual Tech2s that are no different from the ones sold by Vetronix.  Over the years different companies were licensed to produce and sell them.  OTC and Bosch used to as well.

 

Mine came from China last year.  So far so good.  Got the case and made sure it had the last software update, 33.004 for the PCMCIA card.  Bought off Aliexpress and arrived in half the time quoted via DHL.

 

Don't know of a current link, I would check the forums for the latest posts from folks who recently bought them and also look for vendors who have good feedback.  Many guys bought them this year over at the TahoeYukon forum.

 

 

Would it be better to just take it to the dealer? I feel like that would instantly be over $300 for this Tech2 tool though. 

swathdiver Senior Enthusiast

swathdiver

Posted
Posted
1 hour ago, Brewtal66 said:

Would it be better to just take it to the dealer? I feel like that would instantly be over $300 for this Tech2 tool though. 

Faster than waiting for a Tech2, yes.  With this weather where you live I would think it a matter of safety and therefore a more urgent repair now that I think about it.

 

Consider that you have two of these trucks than can benefit from it; once added to your tool box, it will pay for itself in short order.  Pick one up when you can.

PTXer Enthusiast

PTXer

Posted
Posted

All the Tech2s I see on eBay state they are not for trucks.  Anyone have a better source?

Brewtal66 Enthusiast

Brewtal66

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3 hours ago, swathdiver said:

Faster than waiting for a Tech2, yes.  With this weather where you live I would think it a matter of safety and therefore a more urgent repair now that I think about it.

 

Consider that you have two of these trucks than can benefit from it; once added to your tool box, it will pay for itself in short order.  Pick one up when you can.

Luckily right now the heat is working perfectly fine, so it's not a huge rush to get it working where the AC does. But I just hate having something not right or half-assed like this. After the new year and Christmas I'll pick up one of these TechII scanners. Thanks for the help! 

 

sefiroxx Enthusiast

sefiroxx

Posted
Posted

Temp actuator controls if heat is allowed in. Mode actuator controls where air is to go. Passenger has one temp and one mode (with two positions). Driver has one temp and one mode (3 positions).

There may be additional temp/mode for the rear (depending on option).

Old Cadillac trick. Set controls to max, match the actuator to that max and then install. (Open the actuator to set gears manually or create an appropriate voltage and pigtail to the actuator)

Modern actuator typically have 5 wires. A ground (not really needed), two voltage wires (controller chooses which wire gets voltage to decide which direction to move, and a sensor pair of of wires which is used to provide feedback on which position the actuator is in. It's this pair of errors that the tech2 scanner uses to learn wire the actuators are and put them into start position so the controller can be matched)

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