Cadillac Owners Forum banner

98 SLS Uncommon Seat Heater Failure Mode

911 Views 8 Replies 4 Participants Last post by  SLSNUT
I'm hoping to get some help from one of our mediators/gurus on this issue with my 98 SLS with 60K.
After much reading of seat heater failures modes on this site, they are largely failures of the elements, with HI-LO indicators coming on with the button and audible clicks from the controlling relays under the seats.

Where does one look when the indicator lights do not come on and no consequent activity is noted at the relays? I noted this failure on both front seats at the same time when my wife and I tried to use the heaters last weekend. Both rear heaters function however.

I checked the 10 amp mini fuses (#16 and 31) under the rear seat with a VOM and found them good. I am now in need of some direction. Is this a computer brain issue? Is this an item the vehicle diagnostic system can identify?
1 - 9 of 9 Posts
Seems unlikely that both relays would go at the same time. I am assuming that there is no power to the relays. I'd check the power supply to the switches first, then I'd start looking at the FSM wiring schematic and see what may be common to both front seats.
Appreciate your prompt reply ranger,

Not being all that familiar with this car's electrical system, how and where do I look to check power to the switches? Also FSM is Field Service Manual?
Yea, or more correctly Factory Service Manual. It is an invaluable (albeit pricey) resource... ESPECIALLY for issues like these. You can get them @
Both front seat control modules are grounded at the same chassis connection point (G200).

G200 is a ground block located (according to the Service Manual) at "Left front corner of the passenger compartment, under the front of the sill trim plate."
Thanks Jim. By left front corner of the passenger compartment I am assuming the driver side beneath the front door jamb sill plate. Correct?

That is correct; GM has their own language.

That trim piece goes part way up the front of the door opening and you can work your finger tips under the top end and pop the fastener loose. There are 3 more fasteners along the horizontal section that you can pop off also. The horizontal section fasteners will pop apart at what looks like an impossible situation to reinstall. Just rotate the fasteners 90 degrees and they come out of the oblong hole. Easy to do after the first one.
Thanks to Jim and Ranger. I'll try and pick up the FSM this weekend. Sure appreciate your support. Will post when I do more investigating this weekend.

1 - 9 of 9 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.