This is a modification I might do over the summer so it's ready for next winter. Might even get the heater/cooler combo or a heater/massage combo.
To hook this up I imagine I need a relay that is activated whenever the accessories have power. This way the seat heaters cannot be left on when the car is stopped, but can be turn out any time the radio can be operated. (so the engine wouldn't nessesarily need to be running). If I ran power from the battery through the firewall under the carpet all the way to the rear seats and grounded to the floor, I should be able to work with that. I put the relay on the accessory line for activation and hook it to the battery to provide power wen the car is in RUN or ACCY. I should probably put a fuse between the relay and the battery. From there, I should be able to run the controlls off the main cable for each of the seats and I should be in business, right?
-Dan
Sounds like that should work. The only change I would make is instead of fusing between battery and relay, I would have a small fusebox (like the 4-gang GM Packard style ones you can buy at Pep Boys) AFTER the relay off of 87. That way, you can individually fuse whatever accessories you're running. If you're concerned about damage to the feedline from the battery, you can add a fusible link or a maxifuse near the battery, or the front fusepanel battery stud (a better place to go).
i would also consider a timer so that when the seats get to a certain temp they turn off. dont want the leather to burn up!!

Usually those kits include some type of timer and/or a thermal switch. That's a good thought though- worth looking at your seat heaters and making sure that equipment is there.
S10Fan wrote:
Who makes the best kit for this type of add on?
I found some neat ones here: https://www.sportsimportsltd.com/seatheatac.html
Some cheap ones that are just heaters are here: https://www.nwautoleather.com/nwautoleather/seat-heaters.html (in Candian. Dollars).
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i would run a fused wire from the batery to a realy and have a chanell on my alarm designated for turning on the seats. That way you can control the seat on or off whenever you want.