Newbie with ongoing HVAC weirdness. Any ideas? - SOLVED

[Fless]

Also, Dr. Shock has some videos on using the Tech 2 for updating calibrations. I'm not going to go into the difference between using the offline TIS2000 that typically comes with the Tech 2, and using online SPS. That depends on your programming hardware setup. I did all mine using TIS2000 since those calibrations are no longer being updated, and they're all on the TIS2000 disc.

Later in the video (around 7:15) you can see the updated calibration description, where it lists what issues that particular calibration will correct.

 

[mtglick]

Your seat issue may be a problem with the BCM or the DSM, not the PCM. There are multiple calibrations for the various modules and sub-systems. Here are a few of the calibrations that I verified and updated on my '04 (L59 engine):

View attachment 456953

@Fless , that's very interesting. Thanks much for this, would get my vote for a tech sticky (if you folks do that kind of thing here). What's really got my attention are those last three entries--ultimately, that's kind of what I was asking about. If there are custom selections for HVAC calibrations, and they corrupt or get out of alignment, could explain some of the ongoing issues related to how the whole system functions (or doesn't). Will research that further.

 

[Fless]

Here are a couple of threads that might interest you:

This is a listing of some of the Tech 2 owners; many are willing to help local folks that don't have one:

Tech 2 Owners Map

There are quite a few members that have a Tech 2 and there are always people who wish they had one to use so I thought I would post this thread to try and help each other out. If you own a Tech 2 and would be willing to help out another forum member that might be local to you then post up your...

www.tahoeyukonforum.com

The Case for the Tech-2

The Case for the Tech-2 By J. A. Burns, Port Saint Lucie, Florida I first learned the complete necessity of owning a scan tool designed for my given car at the dawn of the computerized automobile, owning and racing a stable of turbocharged Buick Regals. Even only being able to see and work...

www.tahoeyukonforum.com

 

[mtglick]

As to the original issue, I got it fixed this AM, and (spoiler) it wasn't the resistor.

When I pulled the hush panel down, everything looked good, so I left the first resistor in place and just plugged in the new one. No change. Pulled the original resistor, looked at the connections, nada. I had the system powered up and as I was moving wiring around to get the new resistor out of the way, the fan started up. Turned everything off, looked at everything, nothing looked odd, system was now working normally.

I was just on the verge of declaring a gremlin in the first resistor when, for whatever reason, I decided to pull the fan. To be honest, I don't love putting the fans back in, for whatever reason what SHOULD be a quick thing almost always turns into a fight for me, so I hesitated, but figured it would bug me down the road if I didn't check it. Popped the fan out, looked at it, was fine, and as I went to put it back in the mount, I disconnected the fan.

Which was where the problem was.

The vehicle-side fan connector had melted INSIDE the plug. The exterior looked fine, no discoloration or anything that looked off, but it was distorted just enough to create a small arc, which continued to grow as the system pulled more amps over the connection. More arc, more heat, more distortion, until it eventually broke the connection. When I bumped the wire, it moved just enough to re-establish the connection, temporarily resolving the problem. If I hadn't pulled the fan and looked at the interior of the plug, could have been much worse down the road.

The new resistor came with a new pigtail, so I spliced the new connector into the harness, cleaned the pins, plugged everything back in, et voila. Working fan. I let it run for about ten minutes, checked it again, nothing changed, amp draw looked OK, so declaring this one done, at least for now.

Thanks y'all for the assist, moving on to calibrations research.

 

[Joseph Garcia]

I'm glad to read that your issue is resolved. Please add the word "FIXED" or "SOLVED" to your thread's title, to let others who are experiencing a similar issue know that this thread has an identified solution.

 

[jfoj]

Before you claim victory here, I have been down the path of MANY GM vehicles in the 2000-2006 range with the HVAC damper motor problems. You will know when you have a problem as often you will here a "knock, knock, knock, knock, knock, knock" under the dashboard. This usually the HVAC damper motor trying to find its correct position.

I have taken a number of the damper motor controllers apart and cleaned the variable resistance half moon up with rubbing alcohol and contact cleaner.

But the BIGGEST problem with problems with the HVAC on these truck and almost anything GM built from 2000-2006 that had the electrical HVAC damper motors is with the small female terminals in the wiring harness get loose over time and do not make a good connection. The terminals are a PITA to get out of the connector, but you will need to remove the female terminals one at a time and carefully pinch them closed. Then BEFORE you put the terminal back in the connector, you should push the terminal on the damper motor square male pin to make sure it has a good amount of physical resistance to install and remove the female terminal.

Do this for all the female terminals in each HVAC damper motor you can get to. Some are tough because the pigtail is very short and you cannot get easy access to remove the female terminals.

 

[RobertRN]

Also, make sure you body grounding straps are nice, clean and tight. My fan kept turning on and off at random. Could not figure it out. Replaced the resistor twice then one day I was playing with 2 resistors like you were and when I shut the passenger door the fan came on. The shaking of the door wiggled the chassis ground enough to reconnect. So I hunted all of the straps down, (three that I found) cleaned them up and replaced one and this has fixed a multitude of issues in my 04 XL 2500 SLT.