Seat heater - randomly turns on - 986 Forum - The Community for Porsche Boxster & Cayman Owners

elav · 07-03-2021, 05:38 PM

Hello! The heater in the driver's seat has been randomly turning on - has been making me think these summer days are warmer than they actually are. I have swapped the driver's and passenger's seat heater switches and the problem remains - so I can rule out the switch in the center console.

I haven't been able to find an electrical diagram for the heated seats - anyone have one or can point me to the correctly place in the Bentley manual? Seeing as this randomly turns on from an off state, I'm guessing it is either a short between the switch and the relay or the relay is misbehaving. I've read about the heating element shorting out but I can't see how that would turn itself on - assuming there is a relay for this. I'd really like to fix this vs. simply disconnect it so any help is appreciated.

KevinH1990 · 07-03-2021, 06:48 PM

I suggest you that you also swap the relays located under the seats. Here’s information on finding and accessing the relays: https://rennlist.com/forums/996-forum/959628-heated-seat-relay-location.html
Check post #15 of the thread.

elav · 07-04-2021, 01:39 PM

Thanks - sinks that the relay is $200 from our host. I'll swap the relays and if that fixes the problem, maybe the passenger won't have a heated seat!

KevinH1990 · 07-04-2021, 06:40 PM

https://www.youtube.com/watch?v=aCgbTXLpZTU&list=PL8ogZBhXvNybZNzcxzpT72z6e-uZqA-SI&index=5

Check this video series for information on using generic relays instead of the Porsche relays. The series creator (TTGator is his forum name) posts on this site. Although he was adapting 987 heated seats to work in a 986, his technique can likely be used to repair your seats if the problem turns out to be the relay.

Stl-986 · 07-05-2021, 02:11 AM

It wont work, at least not 100%. I know, I came up with the relay wiring. You would lose the low setting.

Now, if it is the relay and you want to replace it cheaper then the factory one let me know. I designed a circuit board setup using standard 30 amp relays that is much cleaner then the one from Help Me DIY.

elav · 07-05-2021, 01:37 PM

Quote:

Originally Posted by Stl-986

It wont work, at least not 100%. I know, I came up with the relay wiring. You would lose the low setting.

Now, if it is the relay and you want to replace it cheaper then the factory one let me know. I designed a circuit board setup using standard 30 amp relays that is much cleaner then the one from Help Me DIY.

Thanks - unfortunately I won't get to this today but I'll do some debugging and let you know if I require your set up. Great info on this board!

Stl-986 · 07-05-2021, 01:47 PM

Just keep in mind the factory will give you High & Low temps but my solution only gives you High. This is cause there is actually a circuit board in the actual switch and I didn't spend the time (or want to) to figure out the tracing.

Now, if your relay in one seat is bad let me know. I would be interested in it. Maybe I can design something cheap to replace it.

elav · 07-11-2021, 04:26 PM

Quote:

Originally Posted by Stl-986

Just keep in mind the factory will give you High & Low temps but my solution only gives you High. This is cause there is actually a circuit board in the actual switch and I didn't spend the time (or want to) to figure out the tracing.

Now, if your relay in one seat is bad let me know. I would be interested in it. Maybe I can design something cheap to replace it.

Switching relays seemed like a lot of work so I simply removed the relay, cleaned up the contacts and pins on the board, reassembled and put it back. For those that are looking to remove this relay, it is held in with a plastic rivet that you have to push the center pin through the rivet to remove. I took the car out for a brief drive and the seat heater was behaving itself - but time will tell. I was expecting a mechanical relay when I opened it up and was surprised to find the following...

Stl-986 · 07-11-2021, 05:03 PM

That makes a great deal of sense. Was wondering how they did it. Also makes sense now given the price of the relays.

if it happens again, find an old school circuit board repair guy in your area. I bet one of the surface mount capacitors/diodes is bad and needing to be replaced. Should be quick work for someone.