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No rear window heating.
Posted: Fri Dec 02, 2011 4:25 pm
by spud350
I'm not getting a voltage at my rear window terminal. I've checked the fuse (bottom right 30A pink one and it seems fine)
Taking the fuse box and the fuse out if I measure across the terminals at the back (blue+white wires) I'm getting the 12v when I press the switch. As soon as I put the fuse back in I don't get the 12v on the wires which would suggest a blown fuse.
The fuse is fine though.
Any ideas?
Cheer Spud.
Re: No rear window heating.
Posted: Fri Dec 02, 2011 5:16 pm
by thedogsbollox
Don't know about that fuse business, maybe clean where the fuse is held. Usually problems with electrics in the tailgate are down to the wiring between the tailgate and the car body. The wires in there get broken real easy. Tis a bit of a fiddly job. There may be a fact sheet on it.
Re: No rear window heating.
Posted: Fri Dec 02, 2011 7:56 pm
by g8dhe
Depending on the year vehicle type and if you have the Digital Air Con. or not there may be more than just the switch involved.
If you have the Digital Air Con, then its always controlled by a relay on the offside bulkhead under the bonnet and that also involves another fuse and is controlled from the Control Panel.
If you have a Manual Air Control then you have a separate switch on the left of the steering wheel which controls the demister directly.
Either way the switch comes AFTER the fuse so if you where measuring the voltage at the fuse, it should always be +12 volts provided the Ignition is on.
I wonder if you were measuring current ? If you took the fuse out and placed the meter across the two fuse connections then your not in the right location to be measuring the voltage, you were really attempting to measure current and that would be controlled by the switch, in which case what you saw is correct.
The best place to measure the voltage is intially on the back window where the connector makes contact to the metal pattern, put the Red lead on the connector and the Black lead to earth with the meter on the 20 Volt range.
Re: No rear window heating.
Posted: Fri Dec 02, 2011 11:29 pm
by spud350
It does have digi air con but that's off. I've measured at the terminal at the back window but there is nothing.(unless I can't get a good earth.). The next step was to see if it was getting power at the fuse box.
I measured at the back of the pink fuse at the bottom right which I thought was the rear window. There are blue/white wires going to it and it reads nothing until I press the rear switch, then it measures 12v. Thinking about it I may not have been measuring correctly what I thought I was, but it actually gives the reading I needed. However you saying the switch comes after the fuse has thrown me.
I'll have to trace the wire from the fuse box to the rear window and check for continuity. Strange that it goes from blue/white to black/red though. Can someone confirm this before I start pulling it apart?
Cheers Spud.
Re: No rear window heating.
Posted: Sat Dec 03, 2011 12:22 am
by g8dhe

As you have the Digital Air Con, then the switch operates the relay, which connects the power from the 30 Amp fuse to the heater. The colour codes can be seen by clicking the little

symbol at the bottom of the page.
Re: No rear window heating.
Posted: Sat Dec 03, 2011 1:13 pm
by spud350
Checked all relevant fuses and can hear the relay clicking over but after 10 mins standing outside called it a day. Flippin' freezin'.
Just gonna check the wiring at the gaiter next as I can't fathom that wiring diagram. It looks like the wire should be blk/yellow but mine is black/red.
Re: No rear window heating.
Posted: Sat Dec 03, 2011 3:16 pm
by dave_aber
I tapped into that line for a pair of heated screenwash nozzles, Bk/Yel on mine. You are on the middle relay of the 3?