Heated seat not working - Help, please

[rivdriver]

Hi, This is my first post. I truly wish someone can help with my 96 Riv. The heated seat will not heat. The button on the door lights up, but no heat in the seat.

There doesn't seem to be any easy access to the element without ripping open the seat. Are there any solutions to my dilemma? I don't want a cold bottom this winter - brrrrr.

[BamaWildcat]

Rivdriver,

I don't know how much your knowledge of automotive electronics is, but there should be a harness you can unplug around the seat/under the seat that sends 12 volts to the butt warmer. If you have 12 volts there, your butt warmer element has opened, and you need a new element. If you do not have 12 volts, you trace back and see if a relay is bad, switch, fuse, etc.

[NTX5467]

As mentioned, if you are getting sufficient voltage to the connection for the heating element, then it would be the culprit. But . . . getting to that point in the diagnosis could take some time and effort.

The electricals on the newer systems is the switch with the indicator light, plus the part of the switch that varies the "warm", "warmer", "warmest" settings for the heat. On most of the late model GM vehicles, you punch the switch successive times to vary the heat setting from what it is when you punch it the first time.

From the switch, there usually is a relay and/or control module that sends power to the heating element(s) in each seat with seat heater elements.

As mentioned, the heating element is part of the seat cover. In some years, you have to buy the entire seat cover to get a new heating element (on some of the current DeVilles, there can be a total of 4+ different heating elements in each seat!). So, knowing how many elements that might be in your seat and which ones might not be working is important. Typically, there's usually one on the seat cushion and one in the seat lean back cushion, both run by the same circuit. Also, each seat has it's own switches and power circuit.

Now, in the situation that you discover the heating element to be bad, it is possible to change just the heating element without replacing the entire seat cover. To do this, you first take the cover off of the seat and turn it over on a work area. You can feel through the backing material in the seat cover to see the dimensions of the heating element, plus see where the wire disappears into the cover.

Now, from this point on, you proceed with caution and at your own risk . . . but this is basically the procedure as detailed in some late model Cadillac service bulletins for non-operating seat heaters.

From the area where the wiring disappears into the bottom side of the seat cover, you carefully and gently put a slit in the fabric laterally from the wiring entry area. Careful to not puncture or slice the outer seating surface (leather is expensive to replace!) as you do this! Then you can carefully pull out the heating element from between the backing fabric and the outer seating surfaces of the seat cover.

The heating element is a flexible item of a particular size. It's about 1/8" thick, if I recall correctly. With the element in hand, you can then head down to a Cadillac dealer, or Buick dealer too, to see if they have any of the heaters in stock, that you might match for size. Seems like the larger ones are about $75.00 each, if I recall correctly. Hopefully the connectors will match what you have too. They might be listed as "service items" for the Riviera too, so that would be something to investigate.

As you might notice, in the body of the heater you can see where the wires snake through the base fabric. It might be possible to trim the one you find to the size of your old one, if it's not too much different--provided you can't get the exact one you need for your car.

For good measure, you might ask the dealership people to get you a copy of the Cadillac DeVille bulletin on replacing the seat heaters.

To reinstall the heating element, you carefully reinsert the heating element into the seat cover assembly, making sure that you get it "flat" and correctly positioned in the cover as you'll be sitting on it later on). I think there's some procedure to close up the slit you made in the inside part of the seat cover, but once you get the cover reattached to the seat, it should not really matter, I suspect.

The key thing is to fully troubleshoot the seat heater electrical system to see just where the problem is. This is one of the things that it might be better to let competent dealership people undertake as they can pull up the repair procedure from online dealership-only GM information sources. This is one of those "some disassembly required" situations just to find out where all of the electrical components, other than the heating elements, reside in the vehicle wiring harnesses.

Also, considering the increased sophistication of the Body Control Module and things it "commands" to happen, it's functions might be an issue in this situation too.

Just some thoughts,

NTX5467

[rivdriver]

You folks are the best! Thank you both for the replies. I am printing them up now and going to pass them on to someone who can tackle this for me. I'll keep you posted on what happens from here.