Heated rear window not working

[MikeS100]

Hi all,

The heated rear window has stopped working in my V70. The light in the button comes on and the mirrors demist ok but it's not clearing any of the rear screen. Rear wiper and 3rd brake light are working fine so I don't think it's the wiring. Any ideas?

Thanks,

Mike

[V70Zig]

First guess.......fuse maybe, not sure which one though.
Just because the others are working.....don't dismiss the wiring...they don't all break in one go........

[MikeS100]

I assumed the whole circuit would be on one fuse so if the mirrors are working it must be ok? I haven't got an owners manual for the V70 so if someone could check if it is all on one fuse or not I would be grateful. Could be a nice easy fix if it does have it's own fuse.

[volvo again]

Think it's more likely to be the wiring especially where it goes into the tailgate near the hinges...Found this post from a few years ago...

...first disconnect the the electrical connections to the screen and check for continuity--ohms scale--Next check the voltage on the disconnected wires.I would say it should be 12v. Be aware that sometimes wires in the harness can break where they flex at the hinges. One of the wires is shown as a full earth in the Haynes V70 manual.

[MikeS100]

Thanks. I'll have a look at the wires at the weekend and see if I can find any damage

[ITSv40]

It is a ten minute test for current at the screen when switched on. If the heaters in the mirrors are working the fuse is ok. If current is not at the screen a broken wire in the loom by the hinge is the most obvious culprit. If the current is to the screen then the heated screen is damaged in some way. My guess is a broken wire.

[SwedishBus]

The wires can break at the lefthand (as you look from the rear of the car) tailgate hinge, both along the hinge itself, and where the harness flexes inside the car above the roof lining.

It's the work of a few minutes to drop the headlining hard plastic trims down to inspect the nearside hinge and harness - as if you were changing the tailgate support strut, but just on the passenger side.

You will need to unclip the rear load area lamp and unplug it, then unscrew 2x fixings in the rear centre plastic trim around it (under 2x small circular covers that can be pry'd out), then 1x screw near the lefthand coat-hook. Prise out the speaker cover first, pull the white plastic trim out about halfway along the lefthand cantrail at the roof trim, then unclip the whole lot out of the car.

The electrical harness and its multiplug are perfectly accessible at this stage, so you should be able to do a good inspection and measurement on it all. It's worth unplugging and pulling the tailgate harness past the hinge and outside the car, then pull the sleeving back to inspect each wire. Almost certainly one or more will be broken.......

[MikeS100]

Thanks for such a detailed write up, that will come in really handy. I'm hoping to get a chance to look at it at the weekend

[SwedishBus]

It sounds worse than it actually is, to access this part of the harness!

Of my two cars, it's the one that has had the most owners and fiddling-about that has failed the harness. The high-mileage, one owner from new (before me) TDI is perfect compared to the 2.5petrol.

It's worth getting some heat-shrink sleeving in-hand before you fix any breaks. The best way to fix this area of the harness is to cut back close to the tailgate and the interior harness multiplug, and solder in a new length of cable for each wire affected. What seems to fail fastest is where any garage has previously "fixed" a fault in this area with crimp-connector sleeves on the cables. This is a dead-loss, and the wires just seem to fall out after a year or two......

The big black cable is the main earth, but it sounds like your problem is the HRW feed, which, if memory serves me at-all, is likely to be a 33Amp yellow with a red tracer wire. The big wires fail first, because they are less flexible and more likely to get scragged each time the hinge closes through the rear body aperture.

[MikeS100]

Thanks SwedishBus. I've got plenty of heat shrink so that won't be a problem. We've owned it since 2008 so I don't think it's been repaired before. The boot gets opened a lot so I shouldn't really be that surprised if the wire has broken. It's been our main family car for the last 11 years and 130k miles (now on 207k), last weekend we bought an XC90 and then the next trip out in the V70 there's a problem! It's like it knows it's retired and it can relax with some issues now! 😂