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e46 cooling system problems - help!

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My e46 wagon (babara) overheated in traffic the other day and I have traced the problem back to the electric fan not coming on.

When I send 12volts to it directly it runs fine so I know the fan is good, but it is not being turned on by the car when the temp goes up.

I also have spare known working fans that work directly on 12volts, but also don't turn on when in the car.

I've checked the big 50amp fuse and its fine, and I've checked continuity on the wire from the fan power connector back to the ecu and it is good with no breaks.

I've replaced the radiator temperature sensor in the bottom rad hose with a known working one but still no luck.

The ac doesnt blow cold and I presume its related?

No codes have shown up on the dash.

Anyone have any idea what it could be - its doing my head in.

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No flow.. could be thermostat or water pump impeller. Have these items been replaced in the past ? Do you want to borrow my infra red thermo tester ?

Edited by B.M.W Ltd

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I realise you've replaced the temp switch but have you bridged the connectors on the plug to make sure you have a full circuit to the fan?

 

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I will check waterpump as I have a spare.

 

I bridged the connecters to the temp switch and fan didnt come on.

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1 hour ago, zero said:

I will check waterpump as I have a spare.

 

I bridged the connecters to the temp switch and fan didnt come on.

i sell quite a few of those electric fans the modules fail 

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Okay so I fixed it.

Thanks for everyones input and help.

Turns out it was a dead module on the fan housing.

I have four of these fans and the modules seem to be dead on three of them, so I wonder if I killed them when I sent 12v directly to them to test them. They all work from a direct 12v, but dont run when connected to the car.

Lucky the fourth one works (I didn't test that one with direct 12v) so car is driveable again.

So my next question is where do I find new modules, or can they be repaired?

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If these are like the late E39 ones, the switch isn't a switch, its a genuine temp sensor.

The ECU reads the temp, and sends a pulse width modulated signal to the module - 12V may be the wrong thing to try 😉

The fans have 12v all the time, and the module adjusts the fans speed based on the signal.

And they have been known to fail a bit 🙂

 

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If the fan came on when you jumped the temp switch/sensor how was the module dead?

 

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25 minutes ago, M3AN said:

If the fan came on when you jumped the temp switch/sensor how was the module dead?

 

It didn't come on when i jumped the sensor.

I swapped in a spare fan that had a working module.

I think on my other spare fans I must have cooked the modules by running 12v to them to test? Or they were already dead, but that seems unlikey.

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Oh, sorry my bad.

And I always use 9v to test 12v circuits since 'straight-from-battery' power is unregulated. Although most vehicle circuitry should support non-continuous 14v it's better to err on the safe side.

 

 

 

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