Rear Window Demister Fault? - Alfa Romeo Forum
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(Post Link) post #1 of 9 Old 19-11-13 Thread Starter
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Rear Window Demister Fault?


I noticed this morning that when I pressed the demister button on the dash the button light came on as normal but the window did not demist/thaw.

Any ideas as to what the fault is? Could it be a fuse?

Many thanks

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It is annoying when one day the rear window defroster (demister) works and the next not.

Try checking the easy items first. Take a look at the fuse, the location of which is likely shown in the vehicles manual. Check to see if the light comes on when the defroster switch is pushed. When you push the defroster switch you are likely to hear a click as the relay makes.

Assuming these items check out, next take a look at the tabs on the defroster. These tabs are normally located along sides of the defroster and connect the unit to the vehicle’s defrost circuit. A separated tab will stop your defroster cold. If you find a loose or hanging tab use the Frost Fighter Defroster Tab Bonding Kit to reattach the tab.

If the tabs check out as attached to the defroster then check to see if you have power at the defroster tabs. A multi-meter or 12 volt test lamp is handy here. Turn on the defroster and place the probes on each tab. You should see 12-13 volts across the tabs.

If you have power to the tabs it means that the defroster circuit is likely functioning and the fault is in the defroster. We have a good trouble shooting guide online here

Let us know what you find,


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As the light is coming on shouldn't be a fuse possible. The wiring going through the loom at the tail gate is a common fault for breaking.
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It's a fault in the loom. I had mine replaced under warranty last year.
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I thought mine had stopped working, turned out there was a layer of dirt/oil on the inside that when in darker conditions and at night with the car behinds light shining it that gave it the impression of having condensation/frost on it that would never go away
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Thanks all. Getting it checked out under warranty on Fri so will keep you posted.
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(Post Link) post #7 of 9 Old 2 Weeks Ago
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I know this was 4 years ago now, but did you find out what the cause was to your demister problem?

I am now having the same problem, checked the fuse and its fine.
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Most likely the wiring loom to the rear tailgate. These cables get stressed when the boot opens then break internally.
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I think the wiring loom stress is manifesting itself in a failed reverse light on my car
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demister , fault , rear , window

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