Running aux fan only...what temperature switch to use?

[MacBudd541]

I have the AC removed from my car but pushing the button bumps the idle up. i push it sometimes when im warming the car up, or bumping the tunes.

[bmwpower]

Ok...here's the diagram. I'm thinking if I cut the line marked, the ECU will not know of the switch being pressed and therefore will not up the idle.

[clavinZERO]

That's bizarre, because my 90 325is with broken A/C system DOES NOT idle bump when I hit the A/C button. When the system WAS intact, the idle DID bump.

[bmwpower]

That's bizarre, because my 90 325is with broken A/C system DOES NOT idle bump when I hit the A/C button. When the system WAS intact, the idle DID bump.

Any idea what is "broken"?

[hoyabmw]

My '90 autox car has no A/C, no mechanical fan, aftermarket electric fan wired into the A/C switch. It bumps the idle when I turn it on, but that's it. No other effects. Don't worry about that.

[Kerrath]

There are a lot of different ECUs for i engines. If some people bump and some people don't bump, isn't it plausible that some of the ECUs trigger an increase in engine rpm and some don't? Just a thought. If I were you, I'd grab a couple different ones or borrow and try them on your engine.

[clavinZERO]

Any idea what is "broken"?

one of my lines blew, so the compressor never engages when I hit the button, but the aux fan does come on with NO idle bump. convenient for now since I am running no mechanical fan.

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Regarding the lower 80/88 aux fan switch, you want:

80/88 degree (from E36 and/or M42 motor apparently, same connector as late model E30): 61 31 8 361 787

[clavinZERO]

EDIT: tested my A/C button today and it does in fact bump my idle even though the compressor is not being engaged... I wonder why I never noticed this before and thought that it did not do that anymore.

So forget what I said earlier about no idle bump, but that part number is for the aux fan switch is still good :P

[pedal2metal]

Just take two of the 3 wires (can't remember what colors-check you wiring diagram) from the temp switch and and scotch-lock 2 seperate wires and run them to a switch. This effectively acts like the temp switch when it activates the fan relay and doesn't bump the idle. I have mine setup to activate the high speed fan relay. You can then turn the fan on whenever you want without affecting the idle and you can turn the fan on manually if the temp switch fails.

[clavinZERO]

just take two of the 3 wires (can't remember what colors-check you wiring diagram) from the temp switch and and scotch-lock 2 seperate wires and run them to a switch. This effectively acts like the temp switch when it activates the fan relay and doesn't bump the idle. I have mine setup to activate the high speed fan relay. You can then turn the fan on whenever you want without affecting the idle and you can turn the fan on manually if the temp switch fails.

+1

[Skafrog]

The only worry I have about doing that is the side effects of having the A/C switch on....idle bump and whatever else goes along electronically with having the A/C on.

Unless I just somehow rewire the switch to only turn the fan on and remove the link to the ECU for the idle bump...I need to look at the diagram again...

Who the hell cares about an idle bump? The fan should be off when you are running, and on when you are in the pits.

[1990m3]

EDIT: tested my A/C button today and it does in fact bump my idle even though the compressor is not being engaged... I wonder why I never noticed this before and thought that it did not do that anymore.

So forget what I said earlier about no idle bump, but that part number is for the aux fan switch is still good :P

electric fan draws a lot of power, it power bumps the idle to increase output from the alternator. Mine does it too...