Need TSB 01850 ?

Does anyone have access to the TSB's for the 2004 Avalanche 1500? It is Date Reported JANUARY 01, 2004 NHTSA Reference #10006580 TSB Reference #01850 Description: DRIVERS OR PASSENGERS HEATED SEATS TURN ON BY THEMSELVES. *MR

I am having the issue while driving or parked and idling that my driver side seat heater will turn on high when it feels like it. I was on hold with the local GM dealer and they would not give me the info and wanted me to bring it in so they could trouble shoot the problem. I do have the original door switches that are not the recessed ones, but I am sure that 90% of the time it comes on, it is not due to me accidentally hitting the button. The other 10% is on me and my fat fingers trying to roll down the window. I watched it today come on twice while in the parking lot and on hold got the service writer. Both times I turned it off and then it came back on with in a minute or so. Is there a way to disconnect just the drivers side, as when the wife is in the truck she likes to keep her heater on. Thanks in advance for any help in keeping my seat cooler.....

Mine have failed like this twice.

Most likely one of the heater units in the driver's seat has shorted out.

Plenty of threads here in the forum discussing this and the repair.

Here is a video from The Seat Shop with some troubleshooting tips.

Wouldn't the heating pad shorting out cause it to turn off? I have also narrowed it down to just the back turning on.

Like I mentioned, I observed similar symptoms to the ones you described.

The first time my system failed, mine would sometimes turn on by themselves without touching a button at all.

This first happened while I was on line at the drive through at the bank during the middle of summer with the a/c running full blast.

Once or twice, I recall the driver's seat back heater getting hotter than I thought it should have.

Finally, I could not get either the driver's or passenger side seat heater to turn on for more than a few seconds before they shut themselves off.

You could hit the button for either seat and the door panel lights would light up for a very short period and then turn off.

The second time mine failed, the entire system would not turn on for more than a second or two before it turned itself off.

Here are some pictures of the seat heater element pads.

This is the heater element for the seat back:



This is a closer shot of the burned out section.

The dark area along the top of the element was burned to a crisp.



This is a picture of the seat bottom heater element. It is the larger of the two elements.



I took these pictures the first time I did this repair.

At that time, the bad element was the seat back heater, which is usually the case, I have come to understand.

I replaced both of them at the same time since I had already purchased the elements.

Two years later, my heaters would not turn on more than a few seconds at a time, so I purchased a new pair of elements and replaced both again.

This time, I found through testing the system, the seat bottom element was the bad one.

I found the seat bottom element had an open circuit with no resistance while the burnt out seat back element from my first round was shorted out and still showed some resistance.

I now have a good replacement pad for the seat back that I will put back for a time I need to do this again.

If one of the elements is defective, it will affect BOTH seats.

When my driver's seat quit working completely, the passenger seat quit working, as well.

It is important to remember that the door switches simply send a SIGNAL to a control module to begin to perform an action and are not directly involved in providing a circuit for that action.

So, when you hit the switch, you are actually telling a module, or controlling computer if you prefer, to begin applying the needed actions to heat the seats and so forth.

The module itself must have certain conditions in place before it will continue toward it's goal of operating the seat heating system.

One may assume that the programmers of that system designed the ability of the module to detect either resistance and/or current levels in an attempt to detect faults in the system that could result in a fire.

Or not.

Either way, if the resistance falls out of spec, due to a short or open condition, the system as a whole may not work as expected.

What we observe might be total non-function or some of the strange behavior that we have seen.

Short answer is, this is a fairly common problem and the most likely cause is a defective seat heater element and the odds are, the seat back heater element in the driver's seat is mostly likely the culprit.

I found the installation videos at The Seat Shop to be very helpful with this repair.

Good luck and let us know what you found out.