Auxiliary Fan & AC

[e30Squid]

I have a few questions regarding the factory Auxiliary (electric) Fan and the Air Conditioning on E30's. I have seached a few times but have not found any definitive answers.

My car is a 1990 325i and the fan clutch and water pump are less than a year old. I have noticed that my auxiliary fan does not run when I turn the AC on in my car. (this is also the time when the temp gauge will start to rise a little). Actually the electric fan will not turn on until the gauge is at the 3/4 mark on the gauge (this only happens at standstill with the AC on). Other than this my temp gauge stays around the 1/4 mark.

My Questions are:

1. Should the Aux Fan run whenever the AC is running?

2. Are there connections that I should check?

3. To me it seems that if my fan doesn't kick on till the 3/4 mark then the lower temp portion of the fan switch isn't functioning properly. Could this be a resistor problem? How do I check?

Thanks in advance for any help/advice.

[tomwas]

My 87 325is is doing the same thing, aux won't kick on til almost in the red zone, like you it happens in slow/standstill traffic.. My tech said the fan should come on when a/c is turned on but offered no resolution to me at the time... Anyone got any ideas for this prob..... Thanks, tomwas

[scottinAZ]

According to my ETM, there is a leg at S228 that goes to the aux fan to kick it on when the AC is enabled. My 87 sedan does this just fine, as it should. This feeds a diode in the Power distribution box that energizes K1 (normal speed relay). This is done independently of the normal fan switch that works off of temperature.

[Brandon12V]

if the fan works when your temp gets to the 3/4 mark, then it should work when you press the a/c button. it sounds like your resistor is done since the low-speed isn't working. when the ignition is in the 'on' position, press your a/c button. If the fan does not come on, check continuity pre- and post-resistor. If you are not getting voltage post resistor, then the resistor is bad. If you do not get power pre-resistor, you have a short somewhere on the harness or one of your fuses blew. PM bimmerteck and tell him i sent ya. He helped me out a great deal when installing my aftermarket fan. He knows his shit.

[e30Squid]

Thanks for all of the info and quick responses...

[tomwas]

if the fan works when your temp gets to the 3/4 mark, then it should work when you press the a/c button. it sounds like your resistor is done since the low-speed isn't working. when the ignition is in the 'on' position, press your a/c button. If the fan does not come on, check continuity pre- and post-resistor. If you are not getting voltage post resistor, then the resistor is bad. If you do not get power pre-resistor, you have a short somewhere on the harness or one of your fuses blew. PM bimmerteck and tell him i sent ya. He helped me out a great deal when installing my aftermarket fan. He knows his shit.

Thanks also, could you tell me where the resistor is located that you mention... tom

[scottinAZ]

Thanks also, could you tell me where the resistor is located that you mention... tom

on the fan itself. follow the wires from the connector, and you will go right to it

[KenC]

I'd also replace your thermostat if your temp is able to fluctuate between 1/4 and 3/4.

[nrubenstein]

The answer is almost certainly the resistor on the side of the fan, which is supposed to keep the fan running at slow speed. Bump the low speed fuse to the same as the high speed fuse and bypass the resistor.

[e30Squid]

The answer is almost certainly the resistor on the side of the fan, which is supposed to keep the fan running at slow speed. Bump the low speed fuse to the same as the high speed fuse and bypass the resistor.

I like the way you think....sound like a good solution till I source a replacement resistor.

[Brandon12V]

resistors are cheap. $25 man!

[tomwas]

The answer is almost certainly the resistor on the side of the fan, which is supposed to keep the fan running at slow speed. Bump the low speed fuse to the same as the high speed fuse and bypass the resistor.

This would be connecting fuse 13 to fuse 18 in the panel ?......

[e30Squid]

resistors are cheap. $25 man!

This is true, but it doesn't mean they have it in stock at your local parts store on Memorial Day.

[nrubenstein]

The a/c works better with the resistor bypassed, anyway.

[scottinAZ]

This would be connecting fuse 13 to fuse 18 in the panel ?......

no, just replace the low speed fuse with one of the same rating (30A) as the high speed fuse. Easy peasy

And yes, the AC works better at low speeds with fan on high, especially here in AZ.