Temp Switch Question

[Jim Lepage]

I'd like to know what is the purpose of each pin on that switch ? On my M50 swapped 318is only the number 1 is plugged and my aux fan doesn't start.



Thanks

-Jim

[FredK]

The auxiliary fan switch is actually two temperature switches, a low temperature and a high temperature switch, housed inside the same sensor. The way the fan switch works is when the temperature gets to 91°C, it turns on the low speed setting of the fan. When the temperature gets to 99°C, it turns the fan onto high speed. Also, when you turn on the AC switch inside the cabin, the low speed setting is turned on.

In the attached picture, you will find the pin out
1 is ground
2 is low speed
3 is high speed

Now, I have no idea why there’s only one wire on your fan switch connector. What color is the single wire that’s coming out of it?

[nando]

most likely the resistor on the low speed circuit is dead. try jumpering the connectors at the switch and see if you can get the high speed to work. alternatively one of the relays could be shot.

of course if you only have one wire it won't work, but I can't tell if that's a language barrier thing or if you have a real problem..

[Jim Lepage]

most likely the resistor on the low speed circuit is dead. try jumpering the connectors at the switch and see if you can get the high speed to work. alternatively one of the relays could be shot.

of course if you only have one wire it won't work, but I can't tell if that's a language barrier thing or if you have a real problem..

Yes my resistor is dead. When I push my AC button nothing happen. I already tested the high speed and it works. So tonight I'll check what is that wire who is alone on my temp switch.

Is there a way to make my temp switch working beside letting the system heating up ? I suppose I could remove it and test it in a bowl filled with hot water ?

[nando]

disconnect the ground wire for the low speed circuit and splice it into the ground wire on the high speed circuit.

it will now only come on at high speed. if you are using it for cooling the car (electric fan conversion) this is a good idea anyway.

[Jim Lepage]

Ok I took a look at it tonight and here's how it's plugged.



1: plugged Brown/Black wire

2: unplugged small wire

3: empty socket


Three wires come from the same place. The Brown/Black plugged at "1", a Black and a Green/Black.

I plugged a wire to my positive battery pole. If I plug it to the Black/Brown the high speed works. If I plug it to the Black nothing happens. If I plug it to the Green/Black I can ear a small click coming from the fusebox. Probably the relay at K1.

How should I plug those wires ? I only need high speed. I also forgot to say, two weeks ago I cleaned up a little bit all the old unwanted AC stuff, maybe I trashed a ground accidentaly. The high speed fan worked fine before that.

[Jim Lepage]

Anyone ?

[Jim Lepage]

I can't figure how to plug those wires.

If:

1 is ground
2 is low speed
3 is high speed

So:

Black wire goes at...
Brown/Black wire goes at...
Green/Black wire goes at...

When I turn the ignition "ON", should I have power coming to one of the three wires I talked before ?

The only way to see if my fan is working is to bring power from the battery. I think the "High Speed" relay is shot because I don't have power coming to the plug beside the driver side headlights and all my fuses are OK.

[FredK]

1 is power: Green/Black
2 is normal speed: Black, goes to normal speed relay K1
3 is high speed: Brown/Black, goes to high speed relay K6.

pin 1 should only be hot in run from unloader relay K7. I mistakenly called it ground.

So, when the temperature is between 91 and 99C, 1 is shunted to 2, and goes to normal speed relay K1 terminal 86. This has the effect of closing the relay and powering the normal speed of the fan.

Above 99C, 1 is shunted to 3, and power goes to high speed relay K6 terminal 86. This closes the relay and powers the high speed circuit of the fan. The hot side of the relay is powered through Fuse 18, which is a 30A fuse. It might have blown?

[Jim Lepage]

1 is power: Green/Black
2 is normal speed: Black, goes to normal speed relay K1
3 is high speed: Brown/Black, goes to high speed relay K6.

pin 1 should only be hot in run from unloader relay K7. I mistakenly called it ground.

So, when the temperature is between 91 and 99C, 1 is shunted to 2, and goes to normal speed relay K1 terminal 86. This has the effect of closing the relay and powering the normal speed of the fan.

Above 99C, 1 is shunted to 3, and power goes to high speed relay K6 terminal 86. This closes the relay and powers the high speed circuit of the fan. The hot side of the relay is powered through Fuse 18, which is a 30A fuse. It might have blown?

Thanks a lot for your help, it's well appreciated. Tomorrow I'll try to plug them at the right places and see if it's working.

If I want only high speed (anyway my resistor is shot and I don't want to replace it). Should I split the Brown/Black wire and plug it to 2 and 3 ?

[Jim Lepage]

One more question. What's the meaning of "hot in run" ?

Thanks !

[FredK]

If I want only high speed (anyway my resistor is shot and I don't want to replace it). Should I split the Brown/Black wire and plug it to 2 and 3 ?

Exactly. You want the switch to turn the fan on from 91-99°C and 99+°C, and the way to do this would be to hook up the brown/black wire to both terminals of the temperature switch.

One more question. What's the meaning of "hot in run" ?

Um, I wasn't thinking that clearly last night. Sorry about adding to the confusion.

Run = Key in ON position. You should see power at 1 in the ON position. When you turn the key to the START position, K7 will interrupt power to unload the electrical system during start.

[Jim Lepage]

Exactly. You want the switch to turn the fan on from 91-99°C and 99+°C, and the way to do this would be to hook up the brown/black wire to both terminals of the temperature switch.


Um, I wasn't thinking that clearly last night. Sorry about adding to the confusion.

Run = Key in ON position. You should see power at 1 in the ON position. When you turn the key to the START position, K7 will interrupt power to unload the electrical system during start.

Ok cool, now I understand well. Tonight I'll plug all the wires at the good places and see if it's work. If not I'll check my relays an fuses.

Thanks a lot for your help Fred.

[Jim Lepage]

All wires are now plugged at the right places and the fan does not work. I have power at the Green/Black wire when ignition is "ON" so I think the problem comes from the relays or the temp switch.

Is there a way to test the relays/switch or I only need to change them ?

[FredK]

Use an insulated jumper wire to bridge positions 1 to 2 and 1 to 3 on the temperature switch connector. If both speeds work, the switch is bad. If neither speed works, something is wrong with the relays or power wiring.

If you apply 12V to terminal 86 on either K1 or K6, and the fan does not turn on, you have bad relays. You may do this by powering pin 2 or pin 3, to activate relay K1 and K6, respectively.