Radiator fan not working

zoe 3619

Hi guys.
I have a 2000 fiat punto which is overheating,and it turns out the radiator fan isn't coming on.
Is there any easy way of telling whether the problem is the fan itself,or the sensor?
Thanks.

biko

Some tests you can do here
http://fiat-punto-cars.info/cooling-and-heating-systems/81-electric-cooling-fan-testing-removal-and-refitting

zoe 3619

biko wrote: »

Some tests you can do here
http://fiat-punto-cars.info/cooling-and-heating-systems/81-electric-cooling-fan-testing-removal-and-refitting

Much appreciated.will have a look at that.

martinr5232

Fan motor is ecu controlled in those but fan motors gave a lot of trouble so did headgaskets though.

zoe 3619

martinr5232 wrote: »

Fan motor is ecu controlled in those but fan motors gave a lot of trouble so did headgaskets though.

Thanks martin.
Fan seems fine,so have a sensor ordered for it.

zoe 3619

So...still having trouble here.
New sensor fitted,and the fans still not kicking in.Mechanic has checked fuses,wiring,relays and the fan itself.
Any ideas on what to try next?Or any way to rewire the fan so it just comes on with the ignition?

martinr5232

zoe 3619 wrote:

So...still having trouble here. New sensor fitted,and the fans still not kicking in.Mechanic has checked fuses,wiring,relays and the fan itself. Any ideas on what to try next?Or any way to rewire the fan so it just comes on with the ignition?

Chances are the ecu is not sending a signal or wiring is broken.

zoe 3619

Thanks so much for replying,martin.
What would the next step be,do you think?
Is there a way to reset dcu?

martinr5232

Its really impossible to know is there any management lights on the dash ??

Is the cooling system building up pressure ??
There is so many reasons for the fan not to work its impossible to say without looking at it.
Are you sure your mechanic knows what hes doing ??

zoe 3619

martinr5232 wrote: »

Its really impossible to know is there any management lights on the dash ??

Is the cooling system building up pressure ??
There is so many reasons for the fan not to work its impossible to say without looking at it.
Are you sure your mechanic knows what hes doing ??

No managements lights coming on.
System was bled today,so should be good.

zoe 3619

So..still having trouble.
I can take the wires from the coolant sensor,join them and the fan works fine.
Have replaced the sensor,and that makes no difference
Is it a bad idea to bypass the sensor and just leave the two wires joined?(fan stays on when the ignition is on)
Guessing everything would still be fused,so safe enough,but maybe the fan motor would burn out after a while?

Irish Steve

OK, we need to step back a long way here, the diagnosis of the problem appears to be fundamentally flawed. From your description, the fan system as such is not faulty

If bridging the sensor brings the fan on, you don't have an electrical issue as such, and the issue would seem to be sensor related, which should have been ruled out by fitting a new sensor, or another possible, the radiator core is in trouble, so the sensor is never reaching the change over temperature. If you have a test meter, then one option would be to connect the sensor to the meter set to the ohm range, and suspend it in water that's being heated, and at some stage before it boils, the meter reading should change to indicate that the sensor has switched. It should show open circuit (on a digital meter that's usually a 1 without any decimal points on the reading) until it reaches activation temperature, and at that point, it should show short circuit (very low or zero ) reading.

If the sensor passes the boiling water test, then there's a possibility that the radiator is partially furred up, and water hot enough to toggle the sensor is never getting to the area where the sensor is mounted, which would mean that the radiator will have to come out to be chemically cleaned, or overhauled to replace the core.

Another possibility is that the thermostat has failed, so it's never opening enough to allow hot water to circulate through the radiator, so the sensor is not bringing the fan on line, even though the engine temperature is too high.

Either of these last 2 possibles will mean that even if you bridge the sensor to get the fan running full time, the engine may still overheat, because the radiator is not being fed enough circulation to allow the water to be cooled, and keep the engine below normal operating temperature.

It looks to me like you need to go back a few steps to determine what's happening at the sensor location in the radiator, and take it from there.

zoe 3619

Thanks loads Steve.
Have been in to the mechanics so many times that I'm losing all faith.
You've given me something new to think about..was thinking it must be an electrical problem
Have a feeling the thermostat was removed before i bought it,so will check radiator.
Other than that,could it be the e.c.u?

Irish Steve

It's not the ECU, in that if you bridge the sensor, the fan works, so the issue is that even though the engine is too hot, the sensor is not getting water in that area that is hot enough to switch it on, hence my suggestion about testing the sensor.

If the sensor works, which I think it will, then the only other possibility can be that the water is not being circulated into the radiator, and the suspects in most likely order are first, the thermostat, second, the radiator core is blocked, and third, a very unlikely one, the water pump is for some reason not circulating water, and I have heard of water pumps that lose their internal fins, but don't leak, but that's very unlikely.

Has the vehicle had a water leak over a long period of time, so the radiator is being topped up regularly. If that is the case, it's possible that there's limescale blocked some of the radiator, which could be slowing down the flow through the radiator. I would be suspicious if the thermostat has been removed that there's an underlying issue somewhere else, like maybe a slight head gasket leak which meant it was constantly being topped up, so limescale.

If there was a leak, has someone put radweld into it, as that may also be an issue, too much, and the radiator could be in trouble.

Hard to diagnose remotely, the only thing that's clear from what you've been posting is that it's Not electrical or the ECU, unless you were given a bad new sensor, and the suggestion of how to test that will prove that the new sensor is good or not