Is there any reason why my cooling fan should stay on, even from cold. Coolant OK. Not overheating. Doesn't happen if ignition key turned on, only when engine is turning. Has the fan clutch got stuck? Any suggestions?

Sounds like a sensor thing to me. Seem to remember a recent post that mentioned something similar, Crazy Eddie perhaps. Have a check with the search option.

I think it is called a "viscous" fan (not sure on the spelling!) It runs off the crankshaft, and so is always turning while the engine is running. The faster the engine is running, the faster the fan turns, and so cools it more. It's good when sat in traffic jams as your engine wont over heat, but it takes a little bit of power off the engine. Then again I could be completly wrong and mines is shagged as well

you have a problem with your engine temp sensor.

 

Do an ECU test, likely you will have an error code 21 showing up.

 

Zee you

 

Henri

I think we have to decide which fan we are talking about...

 

Is it the electrical one that's in front of the AC-condenser or the engine fan?

 

If it's the electrical one, see Henri's post.

 

If it's the engine fan then it's always turning.

The hotter it gets the stronger the viscous coupling is.

 

Maciej

Yes Maciej is too rite - there a different people talking about different things here.

 

You have one Electric fan and one Mechanical or "Viscous" fan In your engine - The Mechanical fan Sucks air thu Rad to help the coolant system this Fan should always be driven UNLESS you are at very high RPM - at this state the ECU assumes you are travelling at a Velocity at which the fan you actually hinder the flow of air due to the high flow rate on the other side. This is not a perfect solution as if you are doing 6K in first you aren't really going to fast - but it was the best nissan could do without making it really complex.

 

The Other Fan the car has (in the engine bay at least ) is the Electic fan - this only operates when the ECU feels the Normal cooling system is not operating effectively enuff to stasify the needs of the driver.

The Air con is a big factor in its operation as its major function is too aid the condensing speed of the AC hense its positioning.

 

The Electric fan should only come on as follows:

A/C off, coolant temp below 219F=off

A/C off, coolant temp above 221=on

A/C on, vehicle speed

A/C on, vehicle speed

A/C on, vehicle speed > 25mph, coolant below 219=off

A/C on, vehicle speed > 25mph, coolant above 221=on

 

 

As you can see it is both Speed and Temp controlled so check the ECU and check the Coolant Temp Sensor (yellow one at front of engine) The Fan will come on if you remove that sensor.

 

Also from the above you can probably tell the fan wont come on very often.

 

Me and Andy had a long conversation about this last night - he has the opposite problem.

 

Z ya

Nico 91TT

This happened to me the other day. I cleaned the contacts and it stopped! Try that first.

 

Simon 90tt

Thanks guys. Checked the eng temp sensor and the spring clip was missing along with half of the yellow plastic cap. Consequently the sensor was not seated properly. I've taped it up and i expect it will be ok now. Strange that the clip would crack off spontaneously like that though.