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How to cure a faulty heated rear window on a GTV

There is a known fault with the GTV heated rear screens, what seems happen is the timer in the rear screen relay stops working and the relay stays on and over a period of years the extra current causes the contacts in the fuse box to overheat which usually just stops the heated rear window from working but could easily cause a fire. The first thing to do is to inspect the fuse for the heated rear window which is in the fuse box under the dash, if you pull the metal tag at the back of the fuse box the fuse box will hinge forward so you can see the fuses better. If there is any signs of the fuse overheating for example bubbling or deformed plastic on the fuses or surrounding area it is time to perform my modification.

The aim of the modification is to remove most of the current from going through the fuse board and this simple modification does exactly that, what we are going to do is fit a relay in the boot to take the current and use the wire from the front of the car as a switch for the relay and then use a new wire from the battery which is handily located at the other side of the boot to provide the heavy duty current that the heated rear window needs

You do need to be able to have a contact at the fuse board for this to work. The first thing you need to do once you have establish that you have a problem is to remove the spare wheel, no really we need to get in the boot.

Next remove the carpet from the bulkhead in front of you, I say remove you just need to pull it down to access the battery compartment area, you do this by unscrewing the white nipples along the roof of the boot and popping out the little fasteners as shown in the picture.
Next you need to locate the heated rear window wire which is in the left side of the boot, once you have located it you need to cut it so both ends are as long as possible.

Next you need a relay we use part number 11130287 and to do a nice job a second hand relay base which we usually steal off a scrap car, its the base of the fan relay you need to cut the wires off so they are as long as possible, while you are there steal a fuse holder as well, again get plenty of wire you need to get one of the small relay switching wires to connect to the big wire that comes from the fuse box at the front of the car, the relay holder will simply clip into the existing relay mounting points.

Using the same diameter wire you need to connect the wire to the windscreen so it can reach the relay holder you have just fitted and connect it to one of the thick wires that come out of the relay base, it does not matter which one you choose, we put some shrink wrap on one of the wires and then solder the two wires together, then slip the shrink wrap back down and heat it up to finish the job nicely.
The other thick wire needs to go to the fuse holder and the fuse holder needs to be connected to the +ve terminal of the battery. The fuse in the fuse holder needs to be 30 amps.

Now we have two really skinny wires left, one needs to be soldered to the wire that originally fed the heated rear screen, the one that came from the fuse box the other needs to be connected to a suitable earth point, you can use the battery earth or it is a bit more professional to use a loop on a bolt through the body to earth the relay.

JP

To check if you have a problem first remove the fuse box cover.

Then locate the tab at the back of the fuse box.

Pull it towards you and the fuse box will hinge down.

Examine the fuse for the heated rear screen and if it has melted, as in this case, then you need to do this modification.

Undo the white fasteners along the top of the boot, and there are some poppers along the base of this section of carpet which need to be removed.

Remove the carper at the front of the boot.

Now you need to locate the heated rear screen wire and cut it, it is light brown with a white tracer.

If you scrounge a second hand relay holder and fuse they can be clipped onto the relays that are already in place.

On top of the +ve battery terminal there are a number of studs that can be used to attach the new power supply too.

Here is a very handy earth for the relay, it is also the MAIN EARTH for the car so make sure you tighten it up properly.

On some relays you get this handy wiring diagram, terminal 30 connects to the battery +ve via a 30 amp fuse, terminal 85 goes to the brown wire with a white tracer that comes from the fuse box that you cut earlier, terminal 86 goes to the earth that you have chosen in the boot, terminal 87 then connects to the brown wire with the white tracer that goes back up to the rear screen.

The relay you need, part number 11130287

A relay base with wires off a scrap Alfa Romeo (look round the battery or fuse box)

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