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Spi Aux Fan: Strange Behavior

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#1 brivinci


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Posted 06 June 2019 - 06:56 PM

I had my 94 SPi in a parade the other weekend and towards the end of the it, my car started getting REALLY hot (was a hot sunny day and where were not even going a walking pace). There was far too much noise around to hear if the aux fan was running but something tells me it wasnt. Heres why. Since the weather over on this side of the pond has started to warm up, I have been driving me Mini a lot more. I've notice the aux fan kicking on when I would not expect it to, like a really cool morning and only a few minutes into a drive...where I have been moving along steadily with no other car in sight. What really makes me wonder is that I have heard the fan kick on and off quickly. Like, come and then switch off after a few seconds. Its my understanding that these should come on at a certain temp and then switch off when it gets several degrees below that temp....so nearly impossible for that to happen in a few seconds.


So, assuming I have an issue, where should I start? The rad is the upgraded super 2-core with screw-in sensor. The aux fan does at least work. There is coolant in the rad with no leaks. I have also installed an aux temp gauge in the car that takes it temp from a sensor mounted in the Minis traditional location; in the head, under the thermostat.

#2 Aria Aradhea

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Posted 07 June 2019 - 05:22 AM

Check that the aux fan wiring is nice and tight, no frays that could cause a short. And just to make sure, check that the aux fan is running well by bridging the wites together. Check the connectors to the switch sensor as well, make sure they're not loose.

If everything's good, you probably would have to consider changing the aux fan sensor.

#3 FlyingScot


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Posted 09 June 2019 - 03:53 PM

It’s a simple set up in an SPi. Thermo switch in radiator to yellow Tyco relay on bulkhead controls it. Not through ECU or anything.

Typical problems are chafed wiring causing sporadic switching. Switch and relay and normally robust and fast on and off most likely wiring.


#4 brivinci


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Posted 10 June 2019 - 08:23 PM

That is what I thinking but always like to check with this lot to be sure;-) 


Cars (and wiring) is in really good nick. The previous 2 owners THANKFULLY did not muck about with the wiring. My guess then is either some rubbing going on and/or those two blade terminals on the switch are loose. Ive never been a fan of them down there, especially with the slightly more proud screw-in sensor vs the clip in type. 

#5 xrocketengineer


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Posted 14 June 2019 - 12:20 AM

Keep an open mind for the unexpected. Mine quit all of a sudden. So I hot wired the fan to test it and it ran fine. I checked for voltage at the fan connector and there was voltage as expected. Reconnected the fan and it did not work. I managed to measure the voltage at the fan connector with it connected and there was no voltage. So, I went to the relay and found no output to the fan. I then checked for power input to the relay with nothing when everything was connected with the fan motor load. It turned out that the purple wire fed by LF-5, somehow, had developed internal high resistance preventing the fan motor from running but if the fan motor was disconnected there was full voltage. The fix was to splice in a new piece of wire going across the bulkhead in between the terminations for the fuse and the relay connector.


Good Luck!

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