964 Heated Seat

[1990C4S]

Mine doesn't work.

Anyone got a circuit drawing or suggestions?


Maybe element has failed?

[1990C4S]

Found it online. Still open to suggestions for normal modes of failure.

[Paul K]

FWIW, when the heated seat in my Range Rover went bad, it was due to cracked wires from seat flex. They pulled off the leather and put a new element sheet in- worked fine then.

Good luck!

Paul.

[1990C4S]

Same as my Volvo. Hoping it is not that. Not a fun job.

[lucittm]

Why does it seem like complaining that my seat heater doesn't work is like complaining that the Beluga caviar is not cold enough?

Anyway, mine don't work either. I changed out one of the Delaying Relays, P/N 928-618-521-02, and it made no difference.

Here is an interesting note. If I am driving along and I HOLD the seat heater momentary switch in the on (up) position, my seat heaters will come on. I tried to control the temperature, but I think this method bypasses the temperature control. Try this and see if you get the same results.

I have not yet been able to obtain a schematic for the Delaying Relay so I cannot troubleshoot the circuit. I may have to reach out to PCNA for some help.

I have already deduced from a visual inspection of the circuit that it uses a variable level of voltage signal through the "temperature" resistor from the +12V "on" switch to power up the circuit for a set temperature and a ground signal to turn the circuit off. Also there is a tempFET to control the temperature of the seat heater elements by controlling the "on" time of the circuit. That is about all I know.

If all else fails, I may put in a manual switch to override the temperature controlled switch with an LED power on light in the dash.

Anybody else having this problem?

Thanks,
Mark

[1990C4S]

Originally Posted by lucittm

Why does it seem like complaining that my seat heater doesn't work is like complaining that the Beluga caviar is not cold enough?

Mark

Depends where you live. Southern US? Yes, you are big time suck. Canada? It isn't a necessity. But it's close.

I will take a look Monday and see what I find. The circuit seems a bit overkill. Very un-Porsche like.

[1990C4S]

Gutted my seat:



To find this broken connector:



The arrow below shows the delaying relay. The box is the connector to the four heating elements in series. To check the elements unplug it and measure the resistance. It should be a few ohms.



I am pretty sure it will work when I re-install it.

[lucittm]

Please let us know if this fixed your seat heaters...

Thanks,
Mark

[1990C4S]

Originally Posted by lucittm

Please let us know if this fixed your seat heaters...

Thanks,
Mark

WIWIT (while I was in there) I found the windshield (I assume that's the source) is leaking into the drivers foot-well area. This will take a few days for investigation, rust remediation, and likely windshield remove and re-install....

[1990C4S]

Big idea popped into my head today. Added an LED to indicate that heat is on. Pics tomorrow....

On the 964 board I feel like I'm tweeting. I am talking but no one is listening.

Opposite of the 911 forum...

[lucittm]

We are all listening but we don't have much to offer. The 964 forum is a bit more sedate. I was thinking about an LED also. I can't believe Porsche did not think of/include that.

Can you also tell us where you tapped into the circuit to light the LED?

Thanks,
Mark

[1990C4S]

Originally Posted by lucittm

We are all listening but we don't have much to offer.

Thanks,
Mark

That doesn't stop people on the 911 board.

I just spliced in to the point where 12 VDC is supplied to the four elements in series (it is hard to see but the grey wire wraps around and goes in tot he connector):



And then mounted a 3/16" red LED in the empty round filler....



So if the LED is on and you don't have heat, the heater element circuit is open somewhere. If you can't get the LED on, the problem is in the supply side. You can also monitor the cycling of the heater, the LED goes on and off as the relay cycles the output.

Final instal pic tomorrow....

[1990C4S]

Drum-roll..........................



The LED is in the centre of the filler panel on right hand side.

A little anti-climactic I guess.

[1990C4S]

I can confirm I have heat in the drivers seat now. And an LED that tells me the 'duty cycle' of the relay.

The only problem is I can't see the LED when I am driving, I have to open the door to see it.

[lucittm]

Mine still don't work after swapping out the seat heat delaying relay. I may have a bad switch. Funny thing is that don't work on either side. . .

Like I said above, the driver's seat will heat up if I hold the switch in.

Mark

[1990C4S]

Originally Posted by lucittm

I may have a bad switch.
Mark

I think so. Is the passenger the same way? Hold the switch and you get heat?

[lucittm]

I'll have to figure out how to sit in the passenger seat while holding the switch and driving at the same time. Oh, that is a scary thought.

Mark

[1990C4S]

Perhaps doing it while parked and idling might be a better idea?