gregeast

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Those of you with seat heaters know that the stock configuration must have been designed by a disgruntled race engineer who was pissed about being assigned to seat heaters. "You vant heat, I giff you heat, macht schnell!".

I call them thermonuclear seat heaters, they get hot in a hurry but then get so hot that you fear a visit from Social Services...

Good news: I found a factory solution that can be retrofitted that allows for variable seat heating.

Bad news: It is embarrassingly expensive.

Here's what you need:

928 618 521 03 Heated seat controller $187.93
928 613 187 04 01c Seat heater switch $94.79

Pricing if from Sunset Porsche as of June 2012

Here's what they look like:



Procedure:

1)Sell your first born, a kidney or those old phone dials you have rotting away in the garage to fund the purchase of the switch and relay, your choice.

1a) Remove the seat. Six hex socket bolts. If I had to tell you that you shouldn't attempt this procedure.

2) Here's a picture of the area we'll be working in:


3)Here's a picture of the old vs. new relay. Old is the white one on the left. You'll notice the pins are in different locations:


4) The new switch/wiring harness has 3 sets of connectors that we need to swap for the old switch/wiring harness.Remove the bezel around the seat heater switch and trace the wires under the seat. Cuss and swear at the lack of room to work. You'll probably have to cut a few zip ties along the way.



5) Harness, Part 1. Here's a picture of the old wiring going to the connector that mates to the relay, followed by a pic of the new wiring and a diagram showing the connections on the new relay. Pop open the connector and the pins slide out/push in easily. Sorry that my diagram and the relay aren't oriented the same. Again, if you can't work this out on your own you probably shouldn't attempt this procedure.






6) Harness, Part 2. This is the big connector that goes from the car to the seat. There's a red and a brown wire from the old wiring harness, remove them and replace with the new red and brown wires from the new switch/harness.


7) Harness, Part 3. The last bit of wiring is to the seat heater pads. Here's a picture of what they look like mounted and a diagram of how it's wired. You have to remove some electrical tape around the stock installation, the wires in question come in on the top part of this picture, the grey wire you see poking out there is a jumper between the two connectors (the connectors still mounted to the plate).



8) Mount the switch in the seat and reattach the bezel.

9) Wrestle the seat back into the car. Pray your touch up paint isn't dried out. Seriously, be patient and careful.

10) Reconnect the two electrical connectors to the bottom of the seat.

11) Next time you're cold, reach down, hit the switch and then spin that dial until you find just the right temperature to make your buns nice and cozy warm.

Van

Nice write up - maybe I need that in the race car?

gregeast

Thanks Van. It's just not a race car w/o variably heated seats.

I'm pretty sure 917's had them. Or maybe that was the heat from the 1000hp motor...

V2Rocket

are you telling me there are places where it gets cold outside?

someone figure how to make air conditioned seats and youll get my attention

gregeast

Why do the San Diego TV stations employ weathermen/women?

Just make a little stand up sign for the news desk that says "Today's high will be 72" and you're good to go. We like a little more variety here at 5280 feet.

ninefiveone

Awesome writeup. Been wondering about this for years (could you just swap a switch and the relay). The wiring is kind of a hassle but isn't a dealbreaker.

Thanks!

gregeast

The wiring is really no big deal, I did the hard part, which was figuring out what wire went where. You have to love German engineering, all the connectors come apart, the wiring harness is terminated in the correct pins and it's basically just plug and play. Anyone notice the connectors to the seat pads have Mercedes logos on them?

Had to track down a late 928 wiring diagram to figure out the relay wiring. This internet deal is gonna be big!

Scott H

I hear it's all the rage over in Europe right now.

Nice write-up. The only car I've ever owned with heated seats was also the oldest and cheapest, a 1992 325is. You don't really "need" heated seats in Florida, but I loved cruising around late at night in winter with the windows down and my buns toasty warm. I even had the nice, thick OEM BMW Sheepskin seat covers to enhance the experience. That last sentence almost sounds like a condom reference.

Van

I actually put an after market heater (it just has high and low settings) in my 996.

OEMTim

Greg, I think you need to borrow my car so that you can do more DIY articles for people.....

docwyte

Yeah, but now your farts won't catch on fire!

User 52121

Cool writeup. If I ever found myself in a position to need to drive my 951 consistently enough on days when seat heaters were necessary I'd be all over this.

Thankfully my truck has heated seats from the factory.

gregeast

"Porsche issued a long overdue recall today after 100's of drivers reported UBI (Unintended Bluedart Immolation). UBI results from the combination of eating Taco Bell in mid-80's vintage Porsches with the stock seat heaters turned on. The fix involves retrofitting variable seat heating from late model 928/964/993 cars."

gregeast

Well done Van, I believe you are now well acquainted with the joys of hog ring pliers.

OEMTim

That reminds me. I need to get some hog ring pliers so I can change out the heating pad in my BMW seats.