DIY seat heater wiring help!

I got a seat in the boneyard to replace mine. The “new” seat has a seat heater grid built in. I checked the continuity, and it’s fine. I’d like to make it work. Has anyone done a DIY wiring? Is it enough to put a (15A?) fused line in, with a rheostat to control the current?

Often, if a certain feature is an option, the wiring connect will already be installed. On the floor board, under the seat, look for a not connected electrical connector. There may have been a control on the floor board, or dash, of the donor vehicle. A wiring diagram would be good to use. Try the back of the repair manual for the wiring diagram.

I’ve never done a DIY on seat heaters but SAAB has used them for 30 years or so. It seems to me that rather than a rheostat you would need a thermostat of some sort. It seems to me a rheostat could work but one wonders what would happen if the heat were turned up and left as it is. I would think there would be the possibility of a fire breaking out in the seat cushion or back unless a thermostat or electronic timer was used to cut the power off after a certain amount of time.

About all I could suggest would be to go over a wiring schematic for your car, whatever make it may be, before jury rigging this.

I would think a 15 or 20 amp circuit would be enough but you can experiment and see if it is. The rheostat idea isn’t practical, you would need a pretty large unit to handle the power. I think the two coils are switched in series for a low setting and then parallel for a high setting.

Yeah, these things suck down a lot of juice. Most manufactures recommend you don’t run the electric rear window/ mirror defrost while the seat warmers are on, else you start blowing fuses…


Back of the envelope I calculate a 1 Ohm 50 Watt rheostat would be about right ($17 online), with a 7.5 or 10 Amp fuse for safety. But I note that most of the adjustable seat heaters use some kind of thumbwheel selector. I would be interested in how that is wired up: some sort of multiple path/resistance circuit board, I would assume.

My guess would be a PWM control. More efficient with very little waste heat being generated across load resistors.

I agree with you TwinTurbo. That would be the way go if a truely variable control was needed.