[ChrisN]

I'm making progress with getting the GTI engine into the Sierra.

I've found one plug on the GTI harness, located near the thermostat housing, that I can't identify. As shown in the pic, it's a similar plug to the other water temp sensors at the thermostat housing (for the ECU, Lg/B and Bl/W) but the plug is grey and the wiring is Bl/Y and W/Bl.

I've studied a few copies of the wiring diagram for the GTI and so far I can't find out what this one is supposed to be connected to. The GTI harness was supplied with the motor.

It's not the ISC solenoid or the canister purge - I have identified those by plug and wire colours.

Any ideas?




Thanks!

Chris

[Gwagensteve]

These are huge and possibly unhelpful guesses, but temp sender for the ecu, or, if that's in place, second temp sender for the a/c, or temp sender for the fans, which are typically not ecu controlled this long ago.

[ChrisN]

Thanks Steve - all good possibles. I have the ECU sensor in place. Probably one of the others you suggest.

I understand the brown sensor (pic below) is the fan, and is a simple switch, so I'll run separate wiring for a fused 12v positive supply (ignition on) to that to trigger a relay to power the thermo fan.

The last one worrying me is the single spade terminal sensor on the right of the brown, which I think is for the dash cluster temp gauge. I'm hoping that is just a simple wire to the gauge as I haven't been able to track down the right wire in the Sierra loom.



PS - anyone got a spare oxygen sensor for the GTI? Or a good source for one?

And buggar - I've just realized I haven't put the thermostat or the gasket into the thermostat housing outlet.

[Gwagensteve]

Yep, just plug the sierra water temp wire onto the single spade plug.

[UBZ]

if that is your engine in the photo , you have a mk2 or mk3 GTI engine .
are you sure you we're looking at the right wiring diagram?

my guess would be an idle up circuit for The AC pump or Power steering pump .