Demister problem
 

So my car (2012 S60) in for service today, left him with a couple of investigative jobs including "the rear demister seems a little slow."

Turns out it's just not working - with the weather recently not having been that cold the cabin heater seems to have been clearing things on it's own slowly.

They didn't spend too long chasing it down today. The garage tell me there's power to the demister so, any thoughts on a likely issue?

When I get a chance I'm going to trace the demister lines for a break and try that conductive paint if I find anything.

Thanks in advance!

Seems unlikely that all of the lines will have gone at the same time so I would concentrate you search on the input and output connections.

Also check the earth connection, power is no good without a good earth.

Thanks whyman. I went to look at it today and there is actually some damage to one of the lines, but that won't explain it's not working as a unit. I'm guessing I have to remove the headliner to get at the electrical connections, has anyone done this?

Did some exploration in the boot area this morning, the fuse certainly seems ok and the fuse box also. I wasn't able to trace the connection from there to the rear window though, either via nearside or offside. Doesn't help when the weather is cold and raining, and there's no obvious way to remove the trim in the cabin - i'm thinking of the parcel shelf and the trim around the C-pillar. Don't want to damage that.

The connection to the tailgate harness is in the boot just beside the fuses. Find the two thickest wires and that's them! The tailgate is synthetic so the earth is part of the harness above the small removable panel behind the main headlining. Check if you can to see if you've a broken wire in the rubber hinge section between the body and tailgate. Check both push on connectors as well. Lower left and right corners.

Thanks xc70virgin - Found the wires alright, just couldn't find or trace them to where they meet the window to see if the tab connection there was ok. IT looks in the S60 as though that connection is hidden behind a trim panel.

What do you mean when you say the tailgate is synthetic?

Sorry to bump this but I'm anxious that anyone with an S60 who can help might see the thread! At this stage I'm looking for help with exploration of the actual tab connection to the heated screen, i.e. with removal of the parcel shelf and/or c-pillar trim.

Any help gratefully received. Thanks all.

On the XC60 the tailgate is not metal. Some type of GRP, glorified plastic.

Put a Multimeter between a known good ground, and the terminals on the desisted.

On a working demister one side will be 12v and the other side 0v or close to it.

Failure modes:
12v and 0v present but no demistt: suspect broken tracks on window. Repair tracks or replace glass.

12v on both terminals: ground wire broken, or bad ground. Check flex loom, the break is normally in the flex part.

0v on both: 12v wire broken, or fuse blown, or relay not working. Check fuse box, relay, power leaving fuse box. Check for break in flex part of loom.

That covers pretty much everything that can happen.

Thanks Swiss, appreciate your advice!

I might try that before I rip the trip off. Though I found a series of pictures that shows a torx screw hidden behind the "airbag" tag on the trim plastic - remove that and it should come off easy enough to check the tabs.