Cooling Fan Speed
 

My cooling fan activates using the demist test and also when auto AC is engaged. Does this confirm that the low spped setting on the fan is working fine or could the high speed fan kick in on these tests if the low speed is not working?

This does indeed indicate the low speed is working if the fan is on constant.

If the fan cycles on and off during the demist test then that is a sign that the low speed has failed and the next speed is tripping in and out as limits are reached.

Just a note, if you fill in your car details on your about me page or include in your avatar it makes it a lot easier to help you with any problems you may be having. :)

You don't appear to have a car Dave6. Is it that of a friends car you are posting your question ??


:smilie_re:That way to your---ABOUT ME.-------------:D

Thanks for the responses. I have a 52 plate 2.5 V6 Connoisseur. By way of an update, the fan comes on with the demist test. Doesn't appear to be that fast. It also comes on with AC on auto and again doesn't appear that fast. I've had the car in diagnostic mode with no AC on and when driving on an open road the temperature is 89-93. In traffic it creeps up and the fan does not kick in and I stopped that test at 105. When I put the AC on in traffic, the temperature returns to 92 before creeping up again to 100 then going down again to 92. Not sure what is going on.

As you probably know the low speed fan should come on at 100 and go off at 96.
Need a diagnostic test on a T4 really

This makes me think that you have a 3 speed fan. When you look through the radiator grille, can you see a silver rectangular resistor with a wire at each end mounted on the fan shroud at about the two o'clock position?

At the moment I'm thinking that you might have a motor brush that is about to fail, but I need more information

Have you just bought this car Dave?

Has any work been done on the cooling system recently?

Simon

I've had the car a few months. Belts, water pump, thermostat were done a few weeks after I bought it. A new radiator was fitted about a fortnight ago. I've tested it again this evening with the AC off and the fan kicked in at 112. Looks like the low and medium speeds have failed I guess. I cannot see a resistor at 2 o'clock.

If there's no resistor then it will be a 3 speed but I refer you back to Dave's post. If you switch on demist and the fan runs constantly then low speed is working, if it cycles on and off there's a problem. How long are you running the "test" for?

I've just run the demist test for 5 minutes. It did not cycle and stayed on constantly. Of course, it could be running at high speed but I have no reference point.

That's excellent information Dave. You are spot-on with your diagnosis. How do I know? because exactly the same thing happened to my car. :D

You appear to have a 3 speed system, as I suspected, and as you've lost low and medium speeds it will be the common earth brush which has worn to its minimum length.

The most cost effective solution is to renew this motor brush. What's your level of enthusiasm for DIY repairs?

Cycling speed applies only to resistor systems which you don't have. So you can forget about that.

Simon