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Radiator fans not kicking in

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This is driving me nuts.

Radiator fans not kicking in.

Found the relay, put new 15a fuse in. Fans run if I short out across the otter switch plug. So thought it must be the otter switch, got new one. Before fitting I plugged it in and held a lighter underneath, fans come on, go off after cooling, come back on when heat applied. Fitted it in situ, quick pull out, push new one in, top up fluid.

Fans still don't kick in, temp gets past the 90 marker then past the next marker (120 ish guestimate) and then up towards 140 at which poit I bottle it and swith her off.

Could it be an airlock, the fluid seems to be circulating, coolant pipes at front of the car are hot.

Please any advice is welcome.

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Which way round do you have the alloy coolant pipe that houses otter switch? Otter should point down otherwise air can be trapped under the switch.

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For the circuit to work you have done the correct procedure relay,fuse , otter switch.

It worked when you used a lighter, so the system checks out,  Air locks can cause the fans not to cut in.

First of all recheck the otter switch again by bridgeing the wires to confirm all still ok.

Could also be faulty temp gauge, as been known,  use an infa red temp gauage on the alloy pipe that houses the otter switch to verify actual coolant temp,  but try bleeding it first to double check.

If all ok,  Run the car up ut before doing so, remove a little coolant from the header tank, so it is half full, or put a bowl underneath to catch coolant when it overflows,  Run the car up with the coolant cap off. 

Any airlock should make its way out and the fans should cut in.  If all ok,  next day when cold top it up,  


A

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When my S1 had the original radiator without the bleed screw, I used to take the front wheels off and lower the front of the car down, supporting the car on the front cross member with axle stands. Also raised the rear up a bit. Filled the expansion take slowly, allowing any air to escape. Ran the car with the expansion cap off and watched for the thermostat to open, then added more coolant as the level dropped. Once topped off, let it run for a bit and then let it cool. With the car back sitting on it’s wheels and level, check the coolant again. It should be about half way up the expansion tank. Never had a problem with air locks using this method.

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Cheers, Gavin

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Just re-reading my post....It doesn’t really come across that the objective is to make the rear of the car higher than the front. So if the car is already up on axle stands, drop the front stands down and increase the height of the rear ones. Idea is to get the radiator at the lowest point so the air is expelled as you fill the system.

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Cheers, Gavin

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Do you 100% trust the reading on your dash temperature gauge?

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Might be a faulty gauge voltage regulator. That would cause the fuel gauge to mis-read as well, is that one working properly?

You could test the gauge by putting the sender in boiling water.

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6 hours ago, Andyww said:

Might be a faulty gauge voltage regulator. That would cause the fuel gauge to mis-read as well, is that one working properly?

You could test the gauge by putting the sender in boiling water.

Ok thanks, I'll give it a go, and yes fuel gauge is dodgy

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