Cooling Fan on and off when not up to Temperature

[morrismen]

Hi,
My wife's V40 2003 Petrol 1.8 SE has an odd issue come about this week. She needs her car for work as a Nurse at the hospital. So I want to see if anyone knows what is causing this problem - she's worried it will break down.

Q: Why the radiator coming on and going off all the time, even when the coolant is cold?

After turning on the ignition and starting the car from cold, the rad fan starts to operate on and off intermittently about every minute, even though the temp gauge says it's still cold. As the Temp rises, the fan still continues to go on and off all the time.

I can't work this out or find any info on it in the forums. Any help appreciated to diagnose this problem.

Thanks all.

[magnuz]

Check that air con is turned off ? Fan will come on if air con is on !

[clarkey1984]

What magnuz said. And also be aware that if the heater controls are set to the windscreen position then the air con will automatically be on, and in fact you can't turn it off unless you set it to a different position other than windscreen.

[LTEcactus]

Worth noting that the SE comes with Climate Control so the AC might be on all the time anyway.

[morrismen]

Thanks for the reply all. The A/C (Climate Control it has) tends to get left on. So I checked the Climate Control On/0. It didn't have any immediate effect. However, it did take a few attempts to switch off each time as though it didn't know the 0 was actually off. Finally it all went off. The air is definitely working as cold and the Climate Control is working. Switched it off and on a few times and it was doing the same on/off on 0.

Decided on the hard reset option. Disconnected the 12V battery for 3 hours and reconnected it. The Radiator Fan now operates normally, and so does the A/C Climate control switch. So for now, it's fixed... I hope.

Thanks all.

[morrismen]

Not sure if this is related, but noticed the car 12v battery had bulged on the +ive terminal. I may be why the car was just catching on a start, but also could be a cause for the Radiator fan cutting in and out. Not sure.

[Technician]

You might want to look at the thermostat. The default for no signal from the thermostat is radiator fan on to protect from overheating so you may have an intermittant signal coming from that, hence the fan cutting in and out. Its quite a cheap part to replace and fairly easy so worth a punt.

[canis]

The thermostat is a mechanical valve device and has nothing to do with switching the fan on. It doesn't even have any wires!

Some V40s had two fans, one which came on with the aircon, as it felt it needed to, the other was for normal engine cooling. What people said about the aircon is correct, it'll start the fan as required, and yes it can work when the engine stopped. The reason i'm saying this is because if you do have two fans, then whichever one is on will give you a big clue. Either it's the aircon or it isn't. The aircon fan is on the left, the cooling fan is on the right, as seen from the drivers seat facing forwards.

[IainG]

Hi

Originally Posted by morrismen

Not sure if this is related, but noticed the car 12v battery had bulged on the +ive terminal. I may be why the car was just catching on a start, but also could be a cause for the Radiator fan cutting in and out. Not sure.

If the battery is starting to play up and you get some dips in voltage, the modules around the car can be affected.
On mine it was the radio, electric windows and one other I can't remember. They used to play up at random times.
The new battery sorted it.
Would be tempted to get the alternator and battery tested, a failing alternator can start to take out the battery.
My car is a later platform but assume some of the modules on the earlier ones can be affected by low voltage. ( especially as you say a reset sorted it)
Iain