# DIY seat heater wiring help! **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [December 18, 2007, 3:44am UTC](https://community.cartalk.com/t/diy-seat-heater-wiring-help/8443 "2007-12-18T03:44:32Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Zumkopf](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/zumkopf/32/5227_2.png) [@Zumkopf](https://community.cartalk.com/u/Zumkopf)\ **Post date:** [December 18, 2007, 3:44am UTC](https://community.cartalk.com/t/diy-seat-heater-wiring-help/8443/1 "2007-12-18T03:44:32Z")
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? ---
**Author:** ![hellokit](https://avatars.discourse-cdn.com/v4/letter/h/6a8cbe/32.png) [@hellokit](https://community.cartalk.com/u/hellokit)\ **Post date:** [December 18, 2007, 5:35am UTC](https://community.cartalk.com/t/diy-seat-heater-wiring-help/8443/2 "2007-12-18T05:35:43Z")
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. ---
**Author:** ![ok4450](https://avatars.discourse-cdn.com/v4/letter/o/e9bcb4/32.png) [@ok4450](https://community.cartalk.com/u/ok4450)\ **Post date:** [December 18, 2007, 5:55am UTC](https://community.cartalk.com/t/diy-seat-heater-wiring-help/8443/3 "2007-12-18T05:55:04Z")
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. ---
**Author:** ![Cougar](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/cougar/32/21348_2.png) [@Cougar](https://community.cartalk.com/u/Cougar)\ **Post date:** [December 18, 2007, 10:53am UTC](https://community.cartalk.com/t/diy-seat-heater-wiring-help/8443/4 "2007-12-18T10:53:30Z")
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. ---
**Author:** ![Baxter\_s\_Dad](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/baxter_s_dad/32/27_2.png) [@Baxter\_s\_Dad](https://community.cartalk.com/u/Baxter_s_Dad)\ **Post date:** [December 18, 2007, 2:53pm UTC](https://community.cartalk.com/t/diy-seat-heater-wiring-help/8443/5 "2007-12-18T14:53:50Z")
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… Benzman ---
**Author:** ![Zumkopf](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/zumkopf/32/5227_2.png) [@Zumkopf](https://community.cartalk.com/u/Zumkopf)\ **Post date:** [December 18, 2007, 3:46pm UTC](https://community.cartalk.com/t/diy-seat-heater-wiring-help/8443/6 "2007-12-18T15:46:18Z")
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. ---
**Author:** ![TwinTurbo](https://avatars.discourse-cdn.com/v4/letter/t/8baadc/32.png) [@TwinTurbo](https://community.cartalk.com/u/TwinTurbo)\ **Post date:** [December 18, 2007, 3:54pm UTC](https://community.cartalk.com/t/diy-seat-heater-wiring-help/8443/7 "2007-12-18T15:54:45Z")
My guess would be a PWM control. More efficient with very little waste heat being generated across load resistors. ---
**Author:** ![Cougar](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/cougar/32/21348_2.png) [@Cougar](https://community.cartalk.com/u/Cougar)\ **Post date:** [December 18, 2007, 10:06pm UTC](https://community.cartalk.com/t/diy-seat-heater-wiring-help/8443/8 "2007-12-18T22:06:41Z")
I agree with you TwinTurbo. That would be the way go if a truely variable control was needed.