Radiator Temp. Sensor

[BonnschE30]

I have an 87 ETA that was previously an auto that had a tranny cooler built into the radiator, and now I'm using an M42 radiator with my swap. I have 2 pigtails for radiator temp sensor that plugged in on my driver's side, one was upper and one lower. The new radiator has the sensor on the passenger's side, so I'm just wondering a couple things...

a) what effect does this sensor have on the cooling system?
b) which of my previous pigtails should I lengthen and connect to the new temp sensor?

PS I know the gauge reads from the sensor on the head, and I have the e30 part swapped in and everything reads accurate.

Thanks guys!

[nando]

it's a thermoswitch, it powers the aux fan (or any electric fan you want to wire it to) with high/low speeds. the stock E30 switch temp threshold is 90/99c, the E36 M42 switch is 80/88c.

[BonnschE30]

I see, thanks for the info and the quickness. So it really doesn't need to be hooked up, but actually it does if I want to keep things a bit cooler when temps rise.

I'm running a m20 mechanical fan and no thermostat right now (somehow ended up with a 92 degree), and I'm breaching 3/4 when out on the road. I'm just trying to work the bugs out of the car, its not a a driver for anyone worried.

I noticed it is a 3-wire switch on the m42 radiator and one of my pigtails on the e30 is 3-wire, the other is 2. Should I just add wire and splice it in?

[Fusion]

Hook it up for sure.
Best cooling results come from buying an 80°c Tstat and 80/88 switch like nando wrote, plus most of us have deleted the viscous (on motor) fan and added a good strong pusher/puller fan in front of the radiator. 99% of higher temp issues are caused by a badly bled system.
Search here, you'll find tons of info on the setups.

[BonnschE30]

Hook it up for sure.
99% of higher temp issues are caused by a badly bled system.

Totally agree, I suppose I will try to splice it into the 3-wire tail from the e30 side as it is a 3-wire switch.

I've bled my system about 4 separate times while diagnosing thermostat problems and thought I was thorough during each of them, but I guess I will get to give it another go when I put an 80 degree part in.

I've searched here and e30tech a ton on cooling issues, and I'm still pretty sure there at least a bit of air in my system. This seems to be a frequent problem, I've tried alot of different ways and will continue to do so until I find an adequate solution.

[BonnschE30]

So I'm not sure how to hook these wires up to the new switch...

The wiring on the e36 switch is brown, green/black, black/grey

E30 had 2 swithches, the wiring for the 3 wire is green/black, green/black, black/brown. 2-wire switch is green/black, black

Any ideas what I should do here? Try to splice all of the E30 wires into the new E36 plug?

[Adrian_Visser]

it's a thermoswitch, it powers the aux fan (or any electric fan you want to wire it to) with high/low speeds. the stock E30 switch temp threshold is 90/99c, the E36 M42 switch is 80/88c.

There are two thermoswitches for the e36 M42. One is the same as the e30.

The 80/88 threshold is part number 61-31-8-361-787-M85

I made the mistake and I have a $60 switch that I don't need. Fucking stealership around here I can't believe it was $60.

[BonnschE30]

good to know, i will see if I can get a PN from my switch to verify if I have the correct one.

still confused as ever about wiring the new pigtail up, damn the auto for having 2 wiring configurations...