Rear window demister fuse blown

Philip624 · 19 November 2018 at 9:11PM

I have a Citroen Picasso and the fuse has blown on the rear windscreen demister heater, tried replacing fuse but it blew straight away. No sign of damage on the lines on the window so I presume wiring must be at fault. Is this an expensive job to fix?

Car_54 · 19 November 2018 at 10:05PM

I suspect cheap to fix, but possibly expensive to diagnose.

Try a Citroen forum - it may be a common fault.

Nilrem · 20 November 2018 at 2:15PM

Car_54 wrote: »

I suspect cheap to fix, but possibly expensive to diagnose.

Try a Citroen forum - it may be a common fault.

Aye if it's a short somewhere in the wiring it's probably pennies to fix, but potentially very time consuming, or difficult to locate.

As you say there may be a common location for the fault that is known about, at a wild guess the first place I would look would be the wiring as it goes from the body of the car to the boot, as that's an area where the wiring will be getting bent/pulled on a regular basis whilst also exposed to the elements to some degree (so highest wear area, and water ingress).
But an owners forum might know of somewhere specific to that model where a cable is likely to wear due to vibration (IE a point where it passes through a bulkhead or over a bolt and rubs).

The only issue is that a visual inspection will be a little difficult unless you can get the plastic sheaving off.

System · 20 November 2018 at 3:57PM

Do not be tempted to replace the fuse with a higher rated one. During my time as an auto electrician I saw a car the AA towed in which wouldn't run. The car kept blowing a fuse so the owner just kept putting in higher and higher rated ones eventually using a bolt. Over time eventually the whole front to rear wiring loom melted and took out a fair chunk of the loom behind the dash as well. The cause? He fitted a high level brake light and took the supply from it from the drivers side rear light cluster. Not a problem with doing that but when he put the light cluster back in he put a screw straight through the middle of the twin core wire supplying the high level brake light and therefore blowing the fuse every time he used the brakes.

End result, car was a write off due to the cost of replacing the entire wiring loom.

AdrianC · 20 November 2018 at 4:24PM

Tarambor wrote: »

Do not be tempted to replace the fuse with a higher rated one. During my time as an auto electrician I saw a car the AA towed in which wouldn't run. The car kept blowing a fuse so the owner just kept putting in higher and higher rated ones eventually using a bolt.

Philip624 · 21 November 2018 at 9:20AM

Thanks all it’s a 13 year old car so don’t really want to spend on it if possible I have seen a few suggestions online for reducing the delisting of windows including devices like dehumidifiers night try one of those to get by on.

Rear window demister fuse blown

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