I’m unfortunately at a bit of a loss. I recently picked up a 2005
Boxster S
and am sorting through some of the small issues. One mystery is the fact that neither of the door mirrors are receiving current, but the rear window defroster is. The button for the rear defroster lights up and the rear glass window gets warm, but I checked the current across the connectors for both right and left mirror—nothing. Fault codes are also being thrown for both mirrors around the heating. Since both the rear window defroster and the mirror heating elements operate off the same switch, I’m assuming there must be a junction somewhere that I can look at? Any guidance would be greatly appreciated!
Here is a wiring diagram for the 987. Probably the same as your car. looks like the rear defogger is controlled by control units, a fuse and a relay and the side mirrors are controlled by control units and a fuse for each side.
I got these off the old files section that I can't find in this new format of this forum.
Thanks for sending these along, very helpful! From what I can tell, the mirror heating is controlled by the driver and passenger door control units which then go to the Gateway module via the CAN Comfort High and CAN Comfort low circuits. I do see that the door control units are powered by two fuses each—I’ve checked all the fuses in fuse block A and they’re OK (I also think windows and power mirrors wouldn’t work at all if these were blown). So this leaves me with a few questions I guess: 1) What are the chances that there would be faults on both left and right door control units for the heated mirrors (probably
next
to none) 2) Could the problem actually be a communication between the Gateway control module and the door control units via the CAN Comfort High and Low circuits (higher % chance of this I think?) 3) Could the problem lie in the defroster switch itself in the Center console? (This would be the least expensive thing to replace).
I’m also wondering what the voltage
should
be across the connectors on the mirrors themselves. I saw somewhere that it should be 12 volts when the rear demister switch is activated but that sounds high?
This is the problem with these kind of diagrams that
Porsche
distributes. They give you just enough information to be dangerous. I looked through diagram and coulden't even find the switch. You just never know what is going on inside the Control Units. One thing that I would suggest if you haven't done it is measure the temperature of the mirror glass with a non contact thermometer and make sure it isn't warming slightly. The mirrors apparantly need less current than the relay controlled rear window. Having said that I would be in the camp that one thing is most likely wrong instead of two.
100% agreed on the diagrams—just enough there to make you dangerous! I wasn’t able to find the actual switch in the diagrams either. I actually haven’t tried using a non contact temp sensor; unfortunately I don’t have one but probably a good excuse to pick one up! I never really thought about observing the temp over a longer period when the defroster switch is on because fault codes for both mirrors are immediately thrown when the switch is activated.
Hi Stephen, I happen to have the same issue on my wife's 2012 Cayenne, were you able to find the problem?
