Stc button folds mirrors...

Resident · Post by **Resident** » 09 Jul 2020, 13:45

Hello all,
I have a strange problem with my recently acquired 2002 V70. For some reason, when I press the STC button it folds/unfolds the power mirrors. The dedicated mirror button acts the same way. However, on at least two occasions, the STC button acted the way it should, i.e. it was on, when the car was started, pressing it would disable/enable the STC system, along with corresponding message in dashboard. Which means the system is ok, well, at least when I am able to access it. I would assume the board got some humidity and is shorting somewhere, but before attempting anything I thought it would be a good idea to ask for your advice/suggestions. Thanks in advance

Post by **oragex** » 09 Jul 2020, 14:15

Hello and welcome.
You have pretty good winters in Lithuania, diabling the STC is pretty important when stuck in snow or climbing a hill. If you can find a local repair place that works with SMD components - may be a TV repair shop - may try to remove the Climate Module unit with the bottom electronic board for buttons, and bring it to them. I would guess someone spilled some coffee and it may need a cleaning or a small repair. You wlll need to keep the car battery disconnected otherwise you will get an SRS light.

Resident · Post by **Resident** » 09 Jul 2020, 14:40

Thank you. We used to have winters a decade or so ago. In recent years it is more like muddy and rainy autumn. But sure, you can never know:)
If I remember correctly, the battery should be disconnected with ignition off an reconected in position II, to avoid Srs errors?

Post by **oragex** » 09 Jul 2020, 15:20

Yes, battery off to avoid SRS light, and with key in POS II to avoid damage to the small cabin temperature sensor - rare but it happened a few times

Resident · Post by **Resident** » 09 Jul 2020, 16:02

Thanks.

Post by **jimmy57** » 09 Jul 2020, 21:17

On P2, the buttons plug into a bus strip that is part of the Climate Control Module. The switch emits a signal that is assigned to that function, the function labeled on the button. You can unplug the switch and put in in any of those positions (IIRC there are 7 positions) that the face cover has openings for and it will do the same function. I had several P2 models and I would move them around so something I used was easier to depress and something I never touched was partly obscured by gear lever. If you have an STC button folding mirrors it is either the switch is sending a wrong or garbled message or the CCM is interpreting it wrong and then sending the wrong message onto CAN low speed network.

Resident · Post by **Resident** » 09 Jul 2020, 21:48

thanks, Jimmy57, I did not know the switches were interchangeable, so it is a good idea to swap them to see what happens. I've seen somewhere that to remove the switches one has to remove the cigarette connector and the plastic behind it. Should I disconnect the battery too, or is that not important as long as the ignition is off and the CCM stays in place/connected?

Resident · Post by **Resident** » 09 Jul 2020, 23:05

I could not resist the urge to try Jimmy's suggestion. Indeed, the switches can be plugged into any active slots, and if they work - they work. Apparently the problem is in the STC switch itself. I disassembled it hoping to see some traces of spill or whatever, but found nothing. Assuming that the signal from the switch is sent via certain combination of "active pins" - I'd assume that something got detached in the switch and it is sending a wrong signal to the board, which is interpreted as a command to fold the mirrors. So I need another, functional STC switch to test the theory:)
Thanks for your comments and ideas.

Post by **oragex** » 10 Jul 2020, 04:44

To remove a switch, just gently pry out the long plastic trim around the switches, start to the sides. Personally I doubt it's a problem with switch location, because you say sometimes the STC button is acting correctly. I once removed my Valet switch and replaced it with a 4C switch (just for the looks, I don't have 4C in my car). Then one day my trunk would not unlock from the trunk release button, so I placed back the Valet switch and things got back to normal.

Post by **vtl** » 10 Jul 2020, 07:54

The button has a resistor matrix that programs its function. I've had a rear headrests folding button, which I don't have, resoldered as auxiliary lights button.

I'd open the button and see what's inside. Maybe it was flooded with Cola or something on that matter.

Sometimes CCM rejects to learn the function of a button. Rearranging them usually helps.