Fan Woes(again)

[dabomb]

Hi all,i`ve posted about this problem before,but didnt get very far trying to solve it,so i`m posting it again,maybe this time somebody might be able to help.

The fan on my 04 290 only seems to come on when i rev the engine.If i keep it reving the fan stays on.Soon as i let it return to idle,the fan stops.It wont come on at all if the engine is left at idle.(boiled over a couple of times today).

What could be the problem??.My first thoughts are either the water pump(because i have to rev the engine to circulate the coolant faster to trigger the thermo),or could it be the thermo itself?,or somthing more sinister?

I could probably fix this by a process of elimination,but that can be expensive.Any help would be much appreciated

Cheers

Edited October 26, 2008 by dabomb

[outlaw dave]

You don't say what year it is, but most likely the fan module part # C039

[ishy]

04 2.9 Dave.

You can eliminate some parts by doing a few simple tests.

You can jump across the two connectors going to the temp sender/thermostat with a paper clip, the fan should be on all the time, if it works well, then the T stat is the only thing out of the system, so that probably is the culprit.

With a test light one end grounded to frame the other to the yellow power wire coming to the T stat, start the motor and see if you have a good light, pick up the idle a little and see if the light gets brighter, not too much or it will blow the bulb in the test light, a good light at idle indicates your probably ok to that point, dull to no light, check for a bad connection, you can trace the yellow wire back and test at first plug in from the motor and all connection with the test light.

Fan, could be getting hung up on the fan shroud, coolant hose, or even a zip tie, I have seen people tie wires, clutch hose, and throttle cable, to the fan shroud, and to make it look neat, push the tie connection under the mount, the fan blade can catch on this.

Also check the fan for side to side play, if the bearings are worn, it could be binding up at low revs.

The fan has nothing to do with the water pump, the water pump is circulating coolant all the time, The T stat is just an on off switch, when the coolant is hot enough, it allows power to go to the fan.

[copemech]

As Ishy said, things to ck. I seem to recall a fellow with a similar condition on a 4t recently, said the regulator fixed it as I recall, obviously shunting off too much voltage at low revs? Just a thought!

[dabomb]

Thanks for the replies.I`l do the checks.Hopefully i`l sort it this time.Cheers