Hi all, I am in the process of converting my GL to injected. I also have the 6 dial dash out of the donor GLT. I have fitted the complete GLT engine bay loom, which included the ex temp sender just behind the bumper.
I have now fitted the 6 dial dash, with my original speedo fitted into it.
The ex temp gauge was , with the ignition off, was sitting on the lowest temp, ie -40. When i turned the ignition on I expected it to show the approx temp in my garage, but it stayed on -40.
Any suggestions?

I need to figure this out too, are the wires in the internal loom going to the dash?

I have half worked it out, the internal loom does not have all the wiring you need. Terminals 6 and 12 on the rh dash connector
Go to wires that end near the steering column, they both have female spade terminals on them, these are the wires that
go to the sender, well in a mk3 with VDO panel anyway. I will be having another look this weekend.

OK, been back on it today. this is what i found with my car, which is a GL with a GLT motor and using the GLT engine loom.
The GL dash loom has two female spade connectors sitting unused, one brown one and one white with black tracer ( the wiring diagram shows this one as black). The temp sender wires in the GLT engine loom which are black and brown, the black wire went to the closest connector block to the heater, it was in the lower centre terminal. Inside the car that connector was not used, so I ran a wire from there to the white/black spade terminal i mentioned earlier, which is connected to terminal 12 of the rh dash connector.
The brown wire ran to the centre connector block,looking from the front, to the rh side 2nd from the bottom. This on the inside of the car had a large white with blue wire on it. I looked at the original GL engine loom and that connection was not used on the GL, ie nothing connected to that large white/blue wire, so i cut the brown wire out of the connector box, joined another peice of brown wire to it, ran it thru the speedo cable hole and connected it to the browm spade terminal that connects to terminal 6 of the rh dash connector. looking at the dash connector I noticed that the brass strip on terminal 12 was flat, so i bent it out a bit, plugged it all back turned the key on and I had a working ambient temp gauge

Note this is the way it worked in my car, which is a 1986 GL, the donor car was a 1987 GLT. Both cars had VDO instruments.