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997 Heated Seat Retrofit Wiring

Paul_S

Monza
Joined
3 Mar 2018
Messages
236
Hi All,

I have almost completed a heated seat retrofit on my Turbo, but need some help locating a connection point or other way of managing the power supply.

The hardest bits of the retrofit have been done. I procured OEM heated seat mats, stripped the seats down and fitted them in, have wired them properly to the seat connector with OEM pins. I have earthed and wired the yellow seat plugs in the wiring loom coming out of the carpet under the seats and run the power cables to the Control Unit under the steering wheel, so the wiring for the seats part is all done. I have of course also added the climate control unit, but apart from the heated seat buttons this plays no part in the wiring as it is all controlled by the Control Unit (Onboard Computer Network Control Unit as Porsche call it) - on RHD drive this is under the steering wheel and above the relay panel.

The final piece is I need to power the seat heaters. So here is what I know:

- Seat Heating is Red/Black wire officially (1.5mm diameter), powered from Pins A2 (right) and B26 (left) of the Control Unit.
- This power supply is shared by the Washer Pump Motor (1.0mm diameter wire) in Pin B23 of the same unit, and connected at 'Terminal 30 Weld Point' somewhere in the passenger footwell
- This Weld Point then connects via a 6mm wire to Fuse F2, an 80A fuse in the Current Distributor box (itself in the passenger footwell, behind the blower motor and ducting).
- Unlike 996, heated seats are not relay controlled, instead they work directly from the control unit

My issue is I cannot locate the Weld Point (known as "SP014_SPS02" on the wiring schematic) - the diagram tells me it is located in Grid reference 7cQ which is the exact opposite location to the Control Unit which is driver side on RHD cars, so this Weld Point will be in the passenger footwell near to the firewall and 5-6 inches in from the side. I am assuming it is perhaps above the blower motor and I'll need to dig around some more removing the glovebox (again) trying to see it. Does anyone know what this Weld Point looks like? What sort of connection type it is?

My alternative options are to barry up the wiring somewhat.

1) As the seat heaters and washer pump share Fuse F2 (80A) alone, and connect at Term.30 , I could tap direct into the existing wiring for the washer pump. However, I have a concern that this is going to be an issue as the existing wire is only 1mm diameter, and I'd need to tap two 1.5mm wires into it. I am assuming this would cause an issue if I powered up the seats (especially both at the same time?) and risk overheating. Can anyone confirm this, as another online guide I read had this as the official process ??

2) I could try and find another power source - per this diagram Fuse F2 (80A) in the Current Distributor has another Red/Black Wire disappearing off to Fuse B10 (25A) which I perhaps could tap into? This makes sense to me as they ultimately share the same Maxi Fuse, but I'm confused why seat heaters would have had their own fuse in the first place so perhaps there is a reason why they have a direct 80A fused connection?

1704444775855.png

My absolute ideal option is to do it OEM and locate the Term 30 weld point in the passenger footwell - it must be above/behind the blower motor assembly and ducting but I don't know what I am actually looking for.

In exciting news, hopefully this will be the final piece of a job I really wish I hadn't started.
 
I think I have found the answer to the Weld Pint question - these are soldered joints connecting multiple wires and covered in heatshrink or similar, and typically just part of the (and hidden in) the wiring loom. Sod trying to find that.

So keeping the same question - can I tap somewhere else? Just seen that Fuse E1 and E2 control the electric seat power and are 30A for each side.
 
de mort may well know, alas he has not posted on here since May 23. He is certainly the font of all knowledge
 

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