Did I get a bad fan switch?

[Ricky G]

I have a 98 Z3 2.8 I was in city traffic and notice my temps starting to climb. I stopped let it cool down. Moving down the interstate temps were steady at 12 o'clock on the gauge. I replaced the fan switch and the fan still doesn't come on. I bled the air and filled the reservoir.
LOW SPEED fan comes on with switch on and A/C on
LOW SPEED fan comes on when using a jumper
HIGH SPEED fan comes on when when using a jumper
so low and high speeds on fan work
I pulled the relays checking for corrosion they looked good but cleaned anyways.
With any one of the relays removed (high speed, low speed or AC compressor) the low speed fan would not work with the AC turned on.
Once all relays plugged in low speed fan works with AC on
Does this mean my relays are all good?
Am I missing something or did I get a bad switch?

[rf900rkw]

You are most likely missing something. The fan switch doesn't care a bit about engine temp.

[Truckeeskibum]

I can't find the link, but I remember a couple of discussion threads about a brown wire leading to the fan or a temperature sensor that was incorrectly wired at the factory.

Your symptoms might be related to that.

[RedRedZ]

Post 6, Randy mentions it

https://www.bimmerforums.com/forum/showthread.php?2207733-Z3-2-8-electric-fan-failure

[saneesh8]

The mechanical fan works fine? Not slipping right?

My car have a sensor screwed to the radiator. This one also controls the high / low speed of the fan. Long time back, to test it, i used a candle or some heat source to heat it and it set the fan running at high speed. I rarely see it running at high speed. Even with AC on at Texas weather.

Low speed fan, on with AC On, it should go on. Also controlled by the DME. High speed, i think AC pressure also turns it on other than the sensor on radiator.

[ProductUser]

There's so much information on how the aux fan works on this site.

A little search...

https://www.bimmerforums.com/forum/s...aux-engine-fan

[DaleSwift]

Depending on the test light you have, the yellow/green will test as 12V+ when "ECTS" is off, [coolant below 194F] if tested at the switch or at the relay and as a ground when "ECTS" is on, [assuming it works].


With that said, the problem with a test light is it can supply the low current ground the relay needs to energize, [turn it on], which in turn will, [should] turn on the rad fan.


Grounding the yellow/green at the "ECTS" is a good way to test the rest of the rad fan circuit, turn ign. switch on then ground the yellow/green, rad fan should turn on, no matter what the engine temp.


I would use a stock "ECTS" although 180 degrees F would probably also be OK, the stock switch is "around" 194 F. My car have a sensor screwed to the radiator. This one also controls the high / low speed of the fan.

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nissan kicks price

[BimmerBreaker]

I would suspect a bleeding issue or a thermostat issue or something personally