C70 2004 (classic) Heated mirrors /rear window stopped working

StijnC70 · Post by **StijnC70** » 16 Dec 2022, 08:55

C 70 convertible 2004 (classic, soft top)
Issue: heated mirrors and rear window stopped working. Switch doesn’t show red light when pushed.
Checked fuses (14 & 29) and although they both seemed in perfect condition, exchanged them for new ones, didn’t work.
Exchanged the switch with one that I’m sure is working (from another car), no result.
Looking at the diagram from the Haynes manual (attached), I checked the wires to the switch (No. 165)). I have power on the blue/black one ( labelled BL/SB in the diagram). According to the diagram, the Y/R wire leads to the “heated rear window/ heated mirror relay” (No. 164), and I suppose this activates the power to the heating. So the only thing I can think of is that this relay must be broken.
Million-dollar question: What is the location of this relay?

Post by **abscate** » 17 Dec 2022, 03:03

If it’s the last year of the P80 chassis in your market it lives here, under dash

StijnC70 · Post by **StijnC70** » 20 Jan 2023, 03:07

So finally had the opportunity to dive in (literally). I can't see a fuse/relay box under the dash. At least not something I can easily access, which looks like the drawing (btw, @abscate, thank you!). See pictures. Should I be able to move the orange or yellow boxes?

Also what puzzles me is that, according to the diagram, the same power line (Y/R) runs to the antenna module and, from there, to the rear window. The antenna works fine (both in going up/down as in giving a good signal). How is that possible? What am I missing?

Post by **abscate** » 20 Jan 2023, 04:26

You come down on that fuse box under hood. Release four Torx T25? Screws and lift the fuse box cover and that exposes the relays. Pictures here...

Post by **misha** » 20 Jan 2023, 05:06

Remove that panel under the dash completely from the footwell and dive in more towards the firewall....it's in the relay box where alarm/immobiliser and seatbelt warning relays are.

Post by **BEJinFbk** » 20 Jan 2023, 16:53

StijnC70 wrote: 20 Jan 2023, 03:07 Also what puzzles me is that, according to the diagram, the same power line (Y/R) runs to the antenna module and, from there, to the rear window. The antenna works fine (both in going up/down as in giving a good signal). How is that possible? What am I missing?

The stock audio system uses two antennas for a feature
called Diversity Tuning. There’s the Main that you can see
and a hidden one that’s a marked on the back of the HU as
a Sub. I can’t recall where the sub is on the C, but if is’s
a coupe and not a convertible, it may be an extra trace
on the back glass. In any case, that sub antenna has a
little amplifier that needs power.

roilo · Post by **roilo** » 30 Jan 2025, 04:10

Hi.

Yes the relay is up there, in practice you have to remove the driver side foot cover, lay on the floor and reach all the way up behind the instrument panel, left to clutch pedal if you have one.

But I wanted to point out that you are reading the diagram wrongly. The Y/R wire comes _from_ the relay (actually timer) to light up the red led light on switch - it origins from the pin 87 that goes to rear window. 87b Y/R goes to mirrors.

What goes from the switch _to_ the relay to activate it for 12 minutes is BL/SB going to relay pin 85. Note that this is ground going to relay coil, on the other end of coil is current from pin 30 (fuse 14) or 15 (fuse 29). When the coil is activated, a lever connected to coil body and having current from pin 30 closes and leads pin 30 current to pins 87 and 87b.

Post by **scot850** » 30 Jan 2025, 13:46

So did you manage to get it fixed?

Neil.

StijnC70 · Post by **StijnC70** » 03 May 2026, 05:44

Hi all,
Did not manage to fix it - yet. Asked 4 different Volvo repair guys here in NL, they were not able to fix it.
Then, finally, I had the tonneau cover motor fixed this week by a specialist I found (set me back € 1300) but this guy could assure me that the fuse is indeed under the dash. So I dove in again (not getting easier growing older) and found it (picture).
Next step is figuring out how to grab & replace the fuse.

: Fuse_box_under_dash

The same guy told me that the annoying relay that keeps beeping when there's something wrong with the cario top, is located there.

Post by **abscate** » 07 May 2026, 02:53

Volvo spent a lot of money on thewiring , cabling, looms, and connectors on these cars in design. The reliability is really good . Most brands 25 years old or more will have electrical failures of all kinds due to component end of life