[butcht2000]

981 with Sport Seat Plus 18-ways. Heated not cooled. There are plenty of threads on this with no real answers. Passenger seat heat not working. Daughter dripped coffee in the button but the AC Controller is fine, tried a new one and same. They problem occurred when It was intermittent. I kept pushing it because it worked some times, I think I over did it and burned the temp control. That where my problem lies, WHERE IS THE THERMISTOR? The wiring diagram appears to show it in the seat heater element (see circle in pic) but it’s not. I bought a new element and it’s not in it element or the harness. Here is what had been checked:

-AC control, fine
-plugged in new element, button turns on then off (same)
-looked in the plugs in the seat and at the seat module and no thermistors (or temp control) anywhere

I’m sure a thermistor is the problem but where is it? I have exhausted every PDF online, PIWIS 3 wiring diagrams, fault finding. I can’t find the info. DOES Anyone know?

 

[foodbiker]

Here's my thought process, @butcht2000 --

1) First, I do believe that the thermistor (aka, NTC) is inside the seat somewhere. Where exactly, I have never found out where Porsche puts them -- and I've researched this topic extensively. You're admittedly in rarified atmosphere here.

2) To quickly rule your issue out, I would consider swapping the driver's and the passenger seat and see what happens. This will quickly help you determine where the fault is at. (Will it destroy your seat? Probably not...but YMMV per any risk involved.) That's what I'd do next.

3) I've learned that the engine has to be running in order to heat the seat (at least in a 987). Just because your AC works on your Climacontrol doesn't mean the heated seats will work -- especially if it is only working intermittently.

4) If your daughter spilled coffee on the switch, dollars to donuts it's the switch (have you disassembled it and cleaned it?) or near the switch. I believe that thermistors are pretty durable and I see no reason to believe that repeated on/off cycles would destroy it.

5) Finally, your absolute best bet before tearing into the seat... is to have a dealer check your codes with a PIWIS and test the connections first...and potentially do a reset. Especially as the 981 seats are visually very tidy, I wouldn't rip mine open unless I absolutely had to -- and completely ruled everything out first -- as they may not look 100% once you put them back together.

Cheering you on in your journey on this and I hope all this helps.


PS - A gentle suggestion to avoid using so many "CAPS" in your title -- especially in a request for help that's not genuinely urgent (like being stranded on the side of the road with your 981, etc.). I know you're frustrated and electrical chasing can cause a few grey hairs - as it certainly has in my case -- but your title really comes across as shouting. Maybe consider editing your title? Hope that makes sense and no offense intended. Cheers and thanks.

 

[deilenberger]

PS - A gentle suggestion to avoid using so many "CAPS" in your title -- especially in a request for help that's not genuinely urgent (like being stranded on the side of the road with your 981, etc.). I know you're frustrated and electrical chasing can cause a few grey hairs - as it certainly has in my case -- but your title really comes across as shouting. Maybe consider editing your title? Hope that makes sense and no offense intended. Cheers and thanks.

+1 - if you can't edit it - let me know and I'll edit it for you. Thanks for your cooperation!

 

[butcht2000]

Here's my thought process, @butcht2000 --

1) First, I do believe that the thermistor (aka, NTC) is inside the seat somewhere. Where exactly, I have never found out where Porsche puts them -- and I've researched this topic extensively. You're admittedly in rarified atmosphere here.

2) To quickly rule your issue out, I would consider swapping the driver's and the passenger seat and see what happens. This will quickly help you determine where the fault is at. (Will it destroy your seat? Probably not...but YMMV per any risk involved.) That's what I'd do next.

3) I've learned that the engine has to be running in order to heat the seat (at least in a 987). Just because your AC works on your Climacontrol doesn't mean the heated seats will work -- especially if it is only working intermittently.

4) If your daughter spilled coffee on the switch, dollars to donuts it's the switch (have you disassembled it and cleaned it?) or near the switch. I believe that thermistors are pretty durable and I see no reason to believe that repeated on/off cycles would destroy it.

5) Finally, your absolute best bet before tearing into the seat... is to have a dealer check your codes with a PIWIS and test the connections first...and potentially do a reset. Especially as the 981 seats are visually very tidy, I wouldn't rip mine open unless I absolutely had to -- and completely ruled everything out first -- as they may not look 100% once you put them back together.

Cheering you on in your journey on this and I hope all this helps.


PS - A gentle suggestion to avoid using so many "CAPS" in your title -- especially in a request for help that's not genuinely urgent (like being stranded on the side of the road with your 981, etc.). I know you're frustrated and electrical chasing can cause a few grey hairs - as it certainly has in my case -- but your title really comes across as shouting. Maybe consider editing your title? Hope that makes sense and no offense intended. Cheers and thanks.

1.Mind numbing there is no info.

2.Good idea, at lest I could rule out anything not in the seat.

3.Yep, engine running.

4.Cleaned the inside and out like new before trying a new ac control.

5.Checked with a PIWIS 3, fault code is short to B+, guided fault is all things I had already checked.

CAPS noted, Sorry first post and I am at my wits end now lol. Thank so much for your reply!

 

[schwinn]

Based on the schematic, the implication is that the thermistor may be within the heated pad in the seat? The easiest thing may be to simply follow those wires and see where they go? I admit, I'm not familiar with where these connectors are, or how easy of a job that would be...

 

[foodbiker]

So yes -- there's a short in there as indicated per the PIWIS. However, if I remember correctly... "B+" is high amperage power that goes to the seat heater...not the controller? You'd have to look.

This being said...You've checked your fuses, right? Silly question, but all my years of wrenching -- this has tripped me up at least once. Keep in mind that the actual power to the seat and the power to the climacontrol would be different -- many more amps to the seat. Basically, it's incredibly likely that it's a relay situation here.

Again, I'd try the seat position swaps first and see what happens. Figure out if it's the seat or in the internal wiring. If it's the latter, you'll have some wire chasing to do.

Finally - again before you do any major digging -- only if you have easy access to the PIWIS again -- maybe do a quick "handover" procedure just to be on the safe side as it might blow out any bugaboos...YMMV.

 

[butcht2000]

Based on the schematic, the implication is that the thermistor may be within the heated pad in the seat? The easiest thing may be to simply follow those wires and see where they go? I admit, I'm not familiar with where these connectors are, or how easy of a job that would be...

That was my thought also but I purchased the element pad and followed the wiring and do see the NTC where it “should” be. I also plugged in the element connectors in place of the original and the light still comes on and goes off. That’s why I don’t thinks the problem is in the seat.

 

[butcht2000]

So yes -- there's a short in there as indicated per the PIWIS. However, if I remember correctly... "B+" is high amperage power that goes to the seat heater...not the controller? You'd have to look.

This being said...You've checked your fuses, right? Silly question, but all my years of wrenching -- this has tripped me up at least once. Keep in mind that the actual power to the seat and the power to the climacontrol would be different -- many more amps to the seat. Basically, it's incredibly likely that it's a relay situation here.

Again, I'd try the seat position swaps first and see what happens. Figure out if it's the seat or in the internal wiring. If it's the latter, you'll have some wire chasing to do.

Finally - again before you do any major digging -- only if you have easy access to the PIWIS again -- maybe do a quick "handover" procedure just to be on the safe side as it might blow out any bugaboos...YMMV.

Yeah I checked the fuses and they are fine. I thought maybe a relay also but I can’t find any relay that had to do with the seat heaters. It also doesn’t have a relay in line any where on the wiring diagram. Just the resistor showing where the seat element is. I have the PIWIS 3 and thought about the handover procedure but didn’t think that would work because the drivers seat works fine. I also recoded the control models already with Ko luck, I didn’t do handover because I didn’t want to reset the PCM but I may still try it. My next try is going to be the seat swap. That will tell me for sure if the issue is on the seat.

 

[schwinn]

I don't know if this helps, but there is some info about seat heaters here: Boxster - Seat Heater Connections and Pathways

I'm also not clear on what you're showing in the pictures. I see two connectors, on with what appears to have 3 wires (the black one) and the other has two (blue). These appear to be off the heating element in the picture? Doesn't that mean that one of those cables might lead to the NTC? I apologize for the dumb question... and not following what's being shown!

 

[butcht2000]

I don't know if this helps, but there is some info about seat heaters here: Boxster - Seat Heater Connections and Pathways

I'm also not clear on what you're showing in the pictures. I see two connectors, on with what appears to have 3 wires (the black one) and the other has two (blue). These appear to be off the heating element in the picture? Doesn't that mean that one of those cables might lead to the NTC? I apologize for the dumb question... and not following what's being shown!

Yeah I’ve read everything pretty much the internet has to say about seat heaters (conversions, mods, repairs, anything that comes up about a seat heater, I’ve read it lol). The pics are of a new seat heater element, I bought it thinking there was an ntc in it and the cause of the heat not working. I can see through every portion of the element pad with a flashlight and there is no NTC. I also plugged the new element pad in place of the one in the seat and it did not fix the problem.

 

[jjrichar]

981 with Sport Seat Plus 18-ways. Heated not cooled. There are plenty of threads on this with no real answers.

Some information that might be helpful below.

Thermistor is in the center seat cushion. ie under your bum. Where I don't exactly know but I expect in the center somewhere. The wiring diagram tells you this is where it is. The 'cushion' is the seat. The 'backrest' is the vertical bit of the seat. Both the cushion and backrest have three separate heated components, center and two bolsters. This is what is shown on wiring diagram.

On wiring diagram, plugs marked X533 and X534 are the individual plugs hidden below the seat. There are numerous of these that go to the different components.

The plug marked X170 is one the plugs that lives inside the big yellow master plug housing under each seat. When you disassemble this big yellow plug there are three separate plugs inside that fit together like a tetris game. X170 is the largest of these. See images below for all of this.

To test the thermistor I would unbolt seat, move forward, then tilt back to get access to the big yellow plug. Disassemble and then test the resistance at pins 1 & 2. I get about 880 k ohm at 20C. Test both seats for comparison. Warm with a hair dryer to test change. If this is all OK then I'd be testing continuity back to the a/c controller.

Video below of how to get access to below seat also below.

 

[butcht2000]

Thank you for your reply and for explains how to test, the pics below is actual the center seat heater element, it sticks on top of the seat cushion on a 981. I purchased it believing that the thermistor was there as the diagram shows but unless it’s much smaller than what I am thinking there isn’t one in it (I used flash lights and pulled the adhesive apart looking to one), I unbolted the seat and disconnected the two heater element harnesses and plugged this one in line but it did not fix it. Bottom still flashes and turns off.

 

[deilenberger]

The thermistor is likely to be quite small. A simple thermistor is typically made up of two wires of dissimilar metal welded together and then packaged in a small dipped-epoxy type housing. It changes resistance in response to temperature (temperature sensitive resistor = thermistor).

The point being - don't necessarily expect the thermistor to be something big that stands out. Follow the wires and you'll find it, or find where the wires disappear to place the thermistor behind the heating element.

 

[jjrichar]

Thank you for your reply and for explains how to test, the pics below is actual the center seat heater element, it sticks on top of the seat cushion on a 981. I purchased it believing that the thermistor was there as the diagram shows but unless it’s much smaller than what I am thinking there isn’t one in it (I used flash lights and pulled the adhesive apart looking to one), I unbolted the seat and disconnected the two heater element harnesses and plugged this one in line but it did not fix it. Bottom still flashes and turns off.

This is frustrating. I had a seat completely stripped to the metal frame with padding, covers, and everything else removed/disassembled less than a week ago. I put it all back together again only a few days ago. Would have been very useful to have the thing apart to check some stuff.

I agree with Don above. I would expect the thermistor to be very small. For example the thermistor in the transmission to detect temperature is about 2mm long. It does seem strange that it can't be easily seen on a fresh uninstalled pad. The two sets of wires show

I'd just be testing the wires. Not just those for the thermistor but the circuits for all the heating elements. I understand the errors point to the thermistor, but from my experience what PIWIS says and means can get a little confused at times. If these seem to be OK and identical to the other seat I can only assume the problem is upstream of the seat.

So I just went and got the seat out of a shipping container and pulled a few things apart to take a look. I'm confused by the pad in your images. The seat I have has only a single wrapped wire strand (contains 4 wires) coming from the cushion pads that goes to a single large black plug like you have. But it doesn't have the blue plug like you. The blue plugs are found within the seat when you pull it apart as these join the different pad sections. When I removed the leather from the cushion it has a single wrapped wire strand going to the center rear portion of the pad like yours, but it doesn't split into two.

The single black plug I have is what I would expect from the wiring diagram and is X534. This has the four wires that are coloured and pinned correctly as per the wiring diagram. The wire colours downstream of this plug (ie that go to the heating pads) are different, but the pinout in the female portion of the black plug is the same so it's pretty simple to test the thermistor in the pad as well as the heating circuit.

Another video that might help. This is disassembly of the 2 way sports plug seat but the cushion is the same setup. Shows the single wire strand coming from the center rear of the cushion. I didn't separate the leather and cushion in this video, but it shows the wiring. Starts at the correct time

 

[butcht2000]

Update- I swapped the seats and can now confirm there is nothing wrong with either seat. Both seats heat and the button lights up if connected to the drivers side. It was backbreaking because the 18-ways are super heavy, but I am really happy that I don't have to take apart the seat (they are CXX option full leather Sport Seat Plus seats, backs, airbag covers, full soft leather). While exciting now I have no clue where to look lol. I have no idea what could have shorted if it wasn't in the AC Controller, seat module, or seat heaters. Thanks for everyones help and input, truly appreciated. Maybe at some point someone will come across this thread and know something else to check.

 

[deilenberger]

@butcht2000 - You mentioned using a PIWIS for some of the diagnostics. I am not familiar with the troubleshooting tools on a PIWIS, but I have to assume it has tools similar to the diagnostics tools I am familiar with - Foxwell NT530, Durametric, iCarScan.. all of these tools are "interactive" - they can tell the modules in the car to perform some actions. And they can also read the "state" of controls - like switches open/closed, plus values from sensors.

Where I'd start -
- Looking at the seat controller:
-- Check the + voltages to the seat controller (any terminal 15 or terminal 30. Engine running, HVAC turned on.)
-- See if there is the option to activate a device (like switching a seat heater on) - if so - do it using the diagnostics tool and see what happens.
--- if there is no heat produced when activated as above - look for a tool that will show the "state" of the switches as seen by the module. IE - if the seat heater switch is pressed does the module KNOW that it's pressed?
-- Going back up a level - read the resistance of the thermistor (temperature sensors) for both left and right seats, or if the tool reports in degrees - read the degrees of each sensor.

Then get back to us with that info.. maybe we can isolate it a bit better. We'll probably need the "Climatronic" module wiring diagram - to know what the connections are and where we should tell you to look... (I don't have a 981, hence no 981 heating diagram..)

 

[jjrichar]

Update- I swapped the seats and can now confirm there is nothing wrong with either seat. Both seats heat and the button lights up if connected to the drivers side. It was backbreaking because the 18-ways are super heavy, but I am really happy that I don't have to take apart the seat (they are CXX option full leather Sport Seat Plus seats, backs, airbag covers, full soft leather). While exciting now I have no clue where to look lol. I have no idea what could have shorted if it wasn't in the AC Controller, seat module, or seat heaters. Thanks for everyones help and input, truly appreciated. Maybe at some point someone will come across this thread and know something else to check.

I'd be checking continuity of wires between the big yellow plug under the seat and the a/c controller. Also check that none are shorted to ground.