2.8 to 1.8 swap question

[Bko]

So I am finishing up my 2.8 to 1.8. I swapped a 1.8t 5spd into my Avant that had a 2.8 auto.

Everything went smoothly just looking to work out a few small things. The biggest issue I am having is radiator fan thermoswitch. The 2.8 car has a 4 wire switch and the 1.8 has a three wire. it didn't look like i could just swap it out in the radiator. the 2.8 one matches the harness in the car it almost looks like it might fit in the coolant flange int the extra spot(just thought of this).any reason this wouldn't work? does anyone have a wiring diagram or have done this before so I can see how to make it work.

[kruftindustries]

If your chassis has a 4 wire, I would say use it. I don't think the fan relay related stuff goes to the ECU though that brings me to the ECU question, that sensor being the easiest, how the hell do all the other sensors work with that swap and how did you swap the ecu and wiring? aren't there 4 knock sensors on that engine and a myriad of other differences like dual n75's and whatknot? If you have the know how to make this work, I'm impressed!

[Bko]

I took the easy route and swapped the ecu and harness from the 1.8t. I had a whole car to pull parts off, so it made it smooth. I've put 50 or so miles on it and everything seems to function. I still havent rewired the electric fan to match the cars harness. I decided to put the 4-wire temp sensor in the coolant flange so hopefully this will work.

[Mad Cow]

The fan switch goes into one of two places on the 1.8t, aeb and atw have it threaded into the side of the rad and AWM has it in the lower rad hose. It would technically work in the coolant flange, but it wouldn't work well. Fan switches need to be as close to the rad outlet as possible to work properly.