Cooling Fan Not Working

[longwkty]

Hi All,

Just a little problem I have with the cooling fan.

It does not cut in when it should so the car could overheat. I have replaced the sensor twice to no avail, I have checked the fan with a direct feed and checked the operation of the relay.

It looks like the sensor is not sending the right signal to the relay and in turn to the fan. Yet the temperature gauge is reading fine.

I read in another post that this could be a faulty ECU, if so how easy is it to replace this?

Regards

longwkty

[t-spiritpete]

Hi mate, it sounds like you have done all the right things to fault find it, as far as replacing the ecu well that could be very expensive. When you say the gauge is working ok do you mean it reads high and the fan doesn't cut in or it just stays in the normal range?

I know it's not the perfect answer but if all fails finding the fault why not put a feed to the fan through to a switch inside the car then if you really get towards overheating you can switch it on manually.

Regards Pete.

[longwkty]

Hi Pete,

Thanks for the reply. The gauge works fine reads temp great runs about half way and goes up when in traffic, cools down when driving normally.

When I first got the car it had a problem where the temp gauge would go up and down, checked the thermostat which had been mangled to stay open so fitted a new one which solved the up and down temp I also checked the diagnostics getting code 22 faulty temp switch so fitted the second sensor and reset the code but still getting the same problem.

I even bumbed in to the previous owner at a supermarket, he approached me as he saw the car (had it for 10years) and he told me that was why he got rid.

I can fit a switch, I just worry about hassle if I sell the car on.

Cheers

longwkty

Kev

[alan333]

It looks like the sensor is not sending the right signal to the relay and in turn to the fan. Yet the temperature gauge is reading fine.

If there's a relay have you checked it, and the power supply to/from it?

How the system works... An engine creates way too much heat and needs cooled down, so coolant is pumped around the engine and absorbs this heat. But the coolant also gets too hot, so it flows to the radiator to be cooled. The radiator cools it by the "ram effect" of the car moving forward, and if there's no ram effect (cos you're stuck in traffic on a hot day) it uses the fan instead. The system then takes "cool" coolant back in from the other "side" of the radiator, and the process is continually repeated. The thermostat decides whether to "send" coolant to the radiator, or to only send it around the engine and heater (like during warm up).

The temp gauge sensor needs to be on the "engine" side to alert "you" if the engine is running too hot, and the fan sensor needs to be on the radiator side so "it" knows whether to kick in the fan or not as necessary. Therefore your temp gauge should read normal, unless either the thermostat or the radiator aren't doing their jobs. Obviously if the radiator isn't doing it's job, it could be a fault in the fan.

Apologies if you already know all this, I'm just trying to be helpful.

[longwkty]

Hi,

Thanks for the reply, i have cheched the relay and all is fine and it runs normally aas you describe. I have put in 2 new sensors but nothing has changed.

Kev

[alan333]

What type of sensor is it? If it's a simple two-wire set-up or a one-wire going to earth, then does the fan kick in when you short it out?

[gazza1286]

The fan should run if you disconnect the wiring on the temperature sensor attached to the radiator. If not then the fan motor could be at fault. As suggested connect the fan wiring directly to the Battery to determine the fault. An auto electrician should be able to sort this out in a few minutes.

[longwkty]

Hi

My car doesn't have a sensor on the Radiator, the only sensor is next to the thermostat housing, I have had power to the fan and it runs no problem.

Thanks

Kev

[longwkty]

The sensor has 2 wires connected to it via a clip on plug.

Cheers

Kev

[gazza1286]

That sensor will have a 'live' side which is fed when the ignition is on. The other wire will only become live when the sensor trips as the coolant begins to overheat. This other wire then becomes the live feed to the fan. Therefore there must be some break in this part of the loom.

Use a circuit tester to identify the live feed to this sensor. Then rig up a new feed from the switched wire on the sensor to the live side of the fan motor. If this works then you will probably need to install a new permanent feed to the fan.

BTW have you have checked the fan relay?

It's worth a try.

[longwkty]

Hi

Thanks for the reply will try and get back

Kev