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Old 12-17-2012, 10:26 PM   #2988
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Joined: Feb 2005
Location: Edge of the Wasatch
Oddometer: 1,333
Originally Posted by crankshaft View Post
Not sure if you guys have covered the rad fan switch or not but I made some discoveries today and thought I would share. The switch on my XCW failed after the first week, so I called the dealer and was told I was SOL but I could get a new one for $54 As fate would have it, my 390 Berg switch was also bad and they happen to be the same. An 84 BMW 318i switch will work and they're offered in 91c and 99c but nobody local has them....of course.

I decided to paw through a friends parts bin at a rally shop and see what I could come up with but found nothing that would work. We decided to chuck the switch into the lathe and pop the cap off and have a look inside. The reason why the switch failed was burned out terminals, the bi-metal disc and popper was fine. My theory is that the switch isn't rugged enough to pass the current for the fan and burns out prematurely. I think the solution is to add a simple relay to the circuit and run a pair of leeds to the fan from the battery directly, with a fuse of course.

The cars that use this style of fan switch all have a relay, so it's obvious to me that it's a start. Probably better for the fan also, since it's not pulling so much amperage through the fan switch. Anyway, there it is
The switch on my '12 EXC failed as well but at more like 3000 miles. I, too, looked into the relay idea as well as another source.

BTW - The dealer price should be closer to $25 as is shown in the fische ...


And, most auto switches were priced similarly so no cost savings.

I noticed that my '07 990 with 32,xxx miles had a similar switch but with wire vs blade connections that has never failed. So it stayed with the OEM switch as being the most simple / cheapest solution & the failure an anomaly. Also, most car fans have larger motors pulling more current hence the relay.

If it fails again soon, it will be revisited.
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