Heated rear window and mirrors not working

dj_efk

dj_efk

A2OC Donor
United-Kingdom
Ok gang - an odd one this:

I’ve suspected for a long time that my heated mirrors don’t work, in addition to the rear window which I’ve known about for a while. The light on the button comes on as it should but nothing else happens (including no drop of voltage registered at the batter via CDIS).

I’ve now confirmed it, so I checked the 30A fuse - looked fine but replaced it anyway, still no worky!

What else could the issue be? I’ve checked past threads but haven’t found the issue of BOTH rear window and mirror heating not working mentioned anywhere…
 
Check if there is 12v output for the rear heater on the aircon module, connector F pin 2 should be +.
Not sure about the mirrors (might be a canbus comm. error) as they are supplied by door controllers and get activated by aircon module through can communication.
 
I've had one before where you could push the HRW button but it wouldn't actually make a contact on the circuit board beneath it in the climate panel, because the board itself was inadequately supported due to a crumbling plastic mounting tower beneath that corner. That said, I don't think the light came on the button when I had that issue. The advice above sounds like an excellent place to start tracing the problem, that should either rule out the climate panel or locate the cause within it.
 
Ok -2 outside this morning and so I had the chance to conclusively prove both the window and mirrors to be out of actuon, despite the light on the button working normally.

How do I remove the climate unit to check the wiring?
 
dj_efk said:
Ok -2 outside this morning and so I had the chance to conclusively prove both the window and mirrors to be out of actuon, despite the light on the button working normally.

How do I remove the climate unit to check the wiring?
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First as I understand it the heated mirrors are activated when the rear screen heater is turned on, so both connected in some way so no surprise both fail together.

To get the climate out you can come at it from above or below.

Either remove radio, release keys to ease out, unhook connectors and remove radio to allow fingers on back of climate to encourage it to pop out.
Or open ashtray, put hands into cubby and make fists and pull cubby out and then fingers on back of climate to pop out. Cubby can be very tight if it has not been out before, I am not strong enough and prefer the radio route, the climate may be reluctant too.

Take care not to scratch or break anything!

Andy

Edit. The above is for single din radio.
 
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Checkout Rear Window Heater Relay, J9.
Mac.

Screenshot 2023-01-17 16.04.28.png
 
dj_efk said:
Is that under the bonnet on a second fuse board or are all those relays hidden above the fuse panel, as it appears from that diagram?
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Sorry I don't know where that relay panel is. Just worked through the schematic to give you a pointer.
I'm sure someone will tell us any minute.
Mac.
 
Yes, above the fuse panel but the trim has to come off. I wrote a from the 'top of my head' How To Remove, I could try and find if interested, there is another somewhere else I remember reading.

Andy
 
Andrew said:
Yes, above the fuse panel but the trim has to come off. I wrote a from the 'top of my head' How To Remove, I could try and find if interested, there is another somewhere else I remember reading.

Andy
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Please Andy - it might be useful if my investigation into the climate unit draws a blank.
 
The only thing the above instructions forgets to mention is the need to unhook the service flap release handle....
 
I haven't checked the relay yet but driving last night I did a scan via CDIS and got a fault for the heated rear window being open circuit - I take it this means a break in the circuit which is either the switch or relay (however I see that the relay doesn't operate the mirrors too - but does operate a bunch of other things which are all working fine - so unlikely to be that I think) - or else a break in the wiring itself.

Any further thoughts appreciated, I will look to pull the climate control out ASAP to check the switch and wiring there.
 
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dj_efk said:
I haven't checked the relay yet but driving last night I did a scan via CDIS and got a fault for the heated rear window being open circuit - I take it this means a break in the circuit which is either the switch or relay (however I see that the relay doesn't operate the mirrors too - but does operate a bunch of other things which are all working fine - so unlikely to be that I think) - or else a break in the wiring itself.

Any further thoughts appreciated, I will look to pull the climate control out ASAP to check the switch and wiring there.
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I was looking for the heated mirror supply, but didn't find it. If it isn't via the J9 relay, how is it switched?
Mac.
 
dj_efk said:
I haven't checked the relay yet but driving last night I did a scan via CDIS and got a fault for the heated rear window being open circuit - I take it this means a break in the circuit which is either the switch or relay (however I see that the relay doesn't operate the mirrors too - but does operate a bunch of other things which are all working fine - so unlikely to be that I think) - or else a break in the wiring itself.

Any further thoughts appreciated, I will look to pull the climate control out ASAP to check the switch and wiring there.
Click to expand...
You check the circuit by looking for 12 volts at the rear screen heater.
No 12 volts, probably relay or switch. If 12 volts, then the element is dead. Might save gaining access to the relay.
Mac.
 
Could be an earth issue rather than power. The wires have been known to break as they pass from the car body roof line into the hatch. I can not remember which side the heated rear window wiring passes through.
 
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