SEAT Toledo W reg. cooling fan

I noticed the other day that the radiator cooling fan keeps speeding up and slowing down when the car is in idle at the end of a journey before I switch off the engine. It seems to start doing this when the engine reaches running temperature. It appears to be putting a large strain on the electrics as the headlights become noticeably dimmer when the fan speeds up. It stops when I switch off. Even if I allow the car to rest for about 15 - 20 minutes to allow the engine to cool before starting it again, the fan starts to do the same thing. The only time I have ever noticed this fan in the past was when it kicked in for a minute or so after switching off the engine in the summer when it was very hot.

Reply to
Bren
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have you checked the coolant level?

Reply to
Mrcheerful

You might want to check the battery. The fan should not cause the lights to dim.

Reply to
Shawn Wilson

The coolant level is well above the minimum mark on the overflow tank. The oil was a bit low so I topped it up. It has not made any difference.

It seems to be doing it now when the temperature is only about 70 degrees. The normal running temperature for this engine is 90 degrees.

I phoned the local SEAT Dealer and spoke to one of their mechanics. They also suggested checking the various levels. Help. I'm baffled!

Reply to
Bren

I assume that the fan is not just coming on because of the air conditioning being on? If not There are several possibilities. Fan running erratically is often a symptom that accompanies a blown head gasket, but if the water level is staying constant then that is unlikely. If the fan is coming on at below normal running temperature then it is likely that the sender is giving a 'wrong' signal, this may be because the sender has gone doolally, OR the sender is OK but (and I have seen this occasionally) the radiator is to some degree blocked, possibly with silt built up around the sender. Have a good look too at the actual radiator condition, if loads of fins are missing then this could cause it too.

Reply to
Mrcheerful

The AC is not on.

I don't think the head gasket is blown. I had a good look around the engine compartment this afternoon and everything appears normal.

Apart from this problem with the fan, the car seems to be running normally.

There is only 55K miles on the car and the radiator looks to be in pristine condition (from the outside). I doubt if the radiator is blocked as I have had the car serviced regularly and the coolant fluid levels are correctly balanced.

Are you talking about the coolant temperature sender and, if so, where is this on the car?

Would plugging the car into one of those diagnostic computers at the dealers show where the fault was?

Reply to
Bren

I do not have any data as to whether the fan is switched by the engine coolant sensor (and then by the ecu) or whether it has its own dedicated switch. If it has a dedicated switch then it is likely to be in the radiator and would have two or more wires to it. I doubt whether a diagnostic would tell you anything new.

Reply to
Mrcheerful

Stick a thermometer on the radiator & see if the fans cutting in at the right temperature. The guage is normally less reliable than the fan thermostat.

Reply to
Duncan Wood

It will on high!

Reply to
Duncan Wood

It would, or should, tell you what the ECU is reading as engine coolant temperature. It may not be the same information that's used for the coolant gauge...

Reply to
DervMan

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