Heated seat voltage/amp requirements, etc

After enjoying the heated seats from my '10 XF for many years, I’m now involved with a restoration project on a mid-80s Mitsubishi Starion and decided to procure seats from a wrecked XF to replace the worn-out Recaros in that car. They have the ability to heat and cool, and the elements work, but I don’t have the touchscreen from that car or any way to control them without simply wiring them up to 12V and letting it rip.

However, we’re loath to do that out of fear that, without the computer to control them, they might overheat and melt the elements. And if you go shopping for 12V rheostats that can handle 25 or 30 amps, you quickly get into some very bulky components.

Our Plan B is not to try to regulate the amount of heat the elements generate, but rather the time they can be on. So basically, instead of variable heat, there would only be one setting (“hot”), but a timer that would force the power off after a set amount of time. In regard to the actual tech inside the seat itself, it’s pretty rudimentary, just fans and heating elements, no magic involved. We just want to make it safe.

My question is how careful do we have to be. In my XF, even on the hottest setting (which was HOT), I never remembered them cutting themselves off. Or if they did, it was after a very long period of time. I also can’t remember whether the fans run in conjunction with the heat, but either way is fine with us.

Basically, if this was your project, and you were determined to use the XF seats and make the heating elements functional, how would you go about doing it? How much do we need to pay attention to the amount of time we let the elements run?

​​​​​​​Jess

Hi Jess, heated seats don’t take that much current. Surprisingly little actually. what do you mean by fans though?

I was under the impression the fan that drives the air through the seat when they’re selected to heat, or especially cool, came from a fan onboard the seat itself, not drawing from the main HVAC system. I may be incorrect about that, of course.

Jess

Sorry, I‘ve missed that the seats are cooled due to focusing only on your final questions, those would need more amps if it’s done that way.
You cannot overheat the heating elements but for the fans I would run a more substantial wire, preferably from the main fuse block or battery with inline fuse to have a neat job.