M42 radiator wiring in early model former M20 car?

[Jand3rson]

Hey guys, got a few questions about wiring an M42 radiator in with my M50 swapped car, formerly an '86 325e (M20 car).

So this is the wiring that used to connect to my old radiator, and those connections were on the driver side:


These are the sensors that those wires connected to, on the old radiator:


And this is the lone temp sensor on the M42 radiator, passenger side:


So obviously that temp sensor has to come out and one of the ones from the old radiator has to take it's place, correct? And that wiring is going to have to be extended to reach the passenger side. My first question is, which one? Second, what was the other one for, and can it be discarded? Was it for the AC fan?

[MR 325]

Josh, you don't need to hook up any of that wiring for your swap.

[jrdeamicis]

If he wants to use the stock wiring for the aux fan he does.

[browntown]

I can't help, but I was under the impression all the radiator wiring was body harness side and it would hook up the same regardless of the engine sitting in front of it. no?

[Jand3rson]

Josh, you don't need to hook up any of that wiring for your swap.

Ooooooh, that's all to control the fan, isn't it? So if I'm running an aftermarket electric fan, I won't need any of that then, right?

[jrdeamicis]

Ooooooh, that's all to control the fan, isn't it? So if I'm running an aftermarket electric fan, I won't need any of that then, right?

No, but you do need to put a temp sensor somewhere to switch the fan.

[Jand3rson]

No, but you do need to put a temp sensor somewhere to switch the fan.

So is that what the one sticking out of the side of the M42 radiator is, in the last pic? If so, do I just swap the one out of the old radiator in its place, and extend the wires over to connect to it?

[jrdeamicis]

The new 3 pin connector temp switch will work fine. If I remember correctly it should be a 12V send and then one pin is HIGH and one pin is LOW. You can just wire the control from the switch to your fan relay.

[JTapper]

The new 3 pin connector temp switch will work fine. If I remember correctly it should be a 12V send and then one pin is HIGH and one pin is LOW. You can just wire the control from the switch to your fan relay.

This is correct.

I wired twin slim fans to the factory wiring. The low temp switch turns one fan on and the high turns on the second. This also made it so I can press the A/C switch and power at least one fan regardless of coolant temp. Wiring this way is super clean.

[Jand3rson]

The new 3 pin connector temp switch will work fine. If I remember correctly it should be a 12V send and then one pin is HIGH and one pin is LOW. You can just wire the control from the switch to your fan relay.

So I need to get the wiring connector that goes into that sensor? Because I don't have it.

[jrdeamicis]

If I dig deep enough in my bins and bins of wiring I am sure I can find you one.

[Jand3rson]

If I dig deep enough in my bins and bins of wiring I am sure I can find you one.

Cool, thanks! Let me know, and I'll pay you for it, if you want.

[jrdeamicis]

This is correct.

I wired twin slim fans to the factory wiring. The low temp switch turns one fan on and the high turns on the second. This also made it so I can press the A/C switch and power at least one fan regardless of coolant temp. Wiring this way is super clean.

I always like running a low temp coolant fan. Just keep it out of mind. My car deals with it self. Not me dealing with the car....

And janderson, I will work on finding it tomorrow.

[MR 325]

If you want to hook the electric fan to an OEM sensor you will need to run the wires. You'll need a different lower temp sensor for the radiator though. If it were me I'd just run a simple aftermarket fan controller.

http://www.summitracing.com/parts/FLX-31147/

Your local auto parts store will sell something similar too.

[browntown]

I'm so confused, I just went into the garage and pressed the a/c switch on my m20 that doesn't have any a/c or condensor fan anymore, and the engine still changes pitch like it is running differently. Clearly I don't understand the fan wiring and will shutup now.