When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I started with HelpMeDIY's videos for the seat heaters but then researched a bit and found the relays were cheap enough on ebay (I think Specialized German has them for around $40 or so each) that it wasnt worth the hassle to daisy chain multiple relays when I could just use the OEM part.
Creating the wiring harnesses for the switches was probably the hardest part. I have a bunch of pics so I'll post that up later with some basic guidance. The most time-consuming part was finding wiring terminals that matched the OEM plugs (so I could keep everything pretty and avoid splicing into existing wiring) and by far the most time-consuming element was just understanding the wiring diagrams.
As I said in my last post, I am working on the assumption that the air pump in my driver’s seat is defective. The used replacement pump arrived today. Because I need to replace the leather on the bolster the upholsterer will be install the pump when he repairs the leather on the seat. I should know by the end of next week whether the pump replacement is the the solution to my non-operational lumbar supports and side bolsters.
I will begin to work on the seat belt receptacle and the seat heater on the passenger seat while I’m waiting for the driver seat repair. I have one of the seat heater relays left over from another project. Instead of fashioning a wiring harness from generic components, I contacted DC Automotive to see what used OEM parts would cost. They are selling the relays for $40 and I was pleasantly surprised to find that the wiring harness was $16.69. With shipping, everything I need for the seat heaters (2 harnesses and 1 relay) is about $88. This may be slightly more expensive than the generic option, but I think I will save time and have a more reliable system using OEM components. I note that in the Help Me DIY video that he was only able to use one heat setting. I am wondering whether the 997/987 seat heaters draw more current than the 996/986 heaters. I hope that’s not an additional challenge.
Last edited by KevinH2000; 03-01-2024 at 01:00 AM.
I am loving mine. They bolt right in to a 996, and presumably to a 986 too. They look great. I like the feel of them. I bought mine from a wreck with a blown thorax airbag on one of them and got a heck of a deal.
For documentation - As I said in my last post, I was waiting on the gateway module form a 981 to connect to my seats to see if I could figure something out as to why my 18-way modules were effectively locked up. I got the gateway module and connected it to the seat via the can hi-lo wires, and the seats started working! For some reason I was not able to connect to the gateway module via a scanner, but it turns out that I didn't need to. I have been told by Porsche master techs on other forums that the seats do not need CAN to function. Unsurprisingly, they seem to be correct. But if the modules can get into a mode where they need to see that CAN just one time to wake up? And after that, they're good? Something to do with the accident that blew the one thorax bag. I don't know. Very happy that my seats work though! To be clear, I only had to introduce the gateway module once on the bench. I do not have the 981 gateway connected to the seats in the car. Heck the module might have just needed to see the 2.5v or whatever (don't quote me) across the can lo and hi lines.
Getting the heating and cooling to work was another whole thing. The heaters just want a PWM +12V like you'd expect. The ventilation wants a PWM signal where the high is when the output is pulled to ground. I bought a little module from AliExpress with heat and cool, and a nice little ****, and for ventilation it wanted to output PWM where high was +12V, and also the PWM duty cycles were way off. I had to make my own little Arduino deal to get ventilation to work. Duty cycle for low, med, high, are pretty close to 100%, so I couldn't just invert the 12V to ground. That would have been too easy.
Could you please elaborate on what the ventilation requires for PWM parameters and what you mean by "The ventilation wants a PWM signal where the high is when the output is pulled to ground"? Would you be willing to share your Arduino files? I've got an arduino and PWM modules I'm planning to use for both the heating and cooling.
I am now at a point where I am planning to move forward with my installation without the lumbar and side bolsters working in my driver's seat. (These functions are operational on the passenger seat.)
As noted in one of my earlier posts, my seats have slightly different wiring than the set that PreppyR6 adapted to his car. Specifically:
1. Where his driver seats had a Blue/Brown wire, my seats had a Blue/White wire. The wiring diagram I posted earlier shows the Blue/Brown wire. In the wiring diagram, it is attached to one of the terminals on the pump motor. I'm assuming that it is a ground.
2. I have additional Brown and Red wires that according to the wiring diagram should provide power and ground to the seat bolster system.
When I wired the seats identically to the configuration PreppyR6 used, with the exception of substituting the Blue/White wire for the Blue/Brown wire, I hear a clicking noise (presumably the valve block), but the pump motor doesn't run.
I have tried the following changes from PreppR6's wiring to see what would happen:
1, I swapped the Green/White wire for the Blue/Brown wire (Blue/White in my car.) I can hear the clicking noise, but the pump motor doesn't run.
2. In one of his "work in progress posts," PreppyR6 said that he, "Disconnected the valve blocks wire (bk/ye in the diagram) and power returned to the entire CU. However, now my issue is that when I connect the lumbar pump motor wires (gn/bk and bu/bn) it's always switched on. So, need to do more testing on it." Based on this, I disconnected the Black/Yellow wire to see whether my motor would switch on. Unfortunately, the pump motor did not run.
To rule out the possibility that my pump was defective, I had a shop replace my pump with a used one that I bought online. This did not lead to a change. Of course, the replacement pump could be defective. I have verified that the switch and the 986/996 seat controller operate the lumbar in my 986 seats.
If anyone has additional suggestions for making the lumbar and side bolster functions operational, I will appreciate it. I don't want to settle for less than 100% operation, but I am at the point where I want to move forward. My current mindset is that if someone suggests a process in the future, even if it is several months from now, I can apply the fix at a later date.
Here's a photo of the harness I made to adapt the 997 seat to work in the 986. The harness takes power and ground from the car and integrates the 986 seat belt connector and the relay for the seat heaters.
Unfortunately, I have been unable to solve the problem with the lumbar and side bolsters in the driver's seat. (Everything works on the passenger seat.) I'm continuing to focus on the air pump in the seat. Based on my crude test, the pump that was originally in the seat is defective. I'm concerned that the used pump I installed as a replacement may also be defective. The best price I could find for a new pump is $400, and I'm not sure I want to spend that much money if I'm not 100 percent sure that will fix the problem.
Overall, I'm pleased with the results, but I would like to rectify the remaining shortfall. I remain open to comments and suggestions.
03-01-2024 | 12:48 AM
