Fan clutch comming on even when the a/c is off.

[TRedwine]

(2003 dodge 3500 six speed manual trans. )The fan clutch will come on even when the a/c is off ,defrost off. Engine will be cold , not at operating temp yet. I replaced the fan clutch a few months ago and this problem has been showing up since then. The reason I changed the fan clutch was because the a/c would not cool when stopped. I did clean the radiator in the front of the engine. Does anyone have any suggestion.

 

[Grayhackle]

My fan comes on all winter. It will do it at random times even when the engine is cold. Many times when I am pulling my trailer hard up the canyon the darn thing will not come on until the temp gauge gets up in the upper range. Many years ago the dealer explained why the thing operated that way but now memory is not serving me right and I can't remember. Maybe someone will explain the operation of the stupid fan clutch to both of us! I will be watching this thread. Anyway, I wouldn't worry about it!!

 

[Joseph Donnelly]

An electrically operated fan clutch (2003-up) may come on as you described; mine does for just a short time when starting out with a cold engine. You probably had DTC P0483 with the old clutch, which you could see on the odometer cluster by cycling the key on-off-on-off-on.

 

[nikwave]

my truck does the opposite,it doesnt want to come on. going uphill it goes to about 215. on flat roads it stays at 190. the fan does spin but never fully egages,or 80-90% like it should. i did change the fan clutch for a new one and still the same. what is the maximum safe temp. for the engine?

 

[Bob4x4]

my truck does the opposite,it doesnt want to come on. going uphill it goes to about 215. on flat roads it stays at 190. the fan does spin but never fully egages,or 80-90% like it should. i did change the fan clutch for a new one and still the same. what is the maximum safe temp. for the engine?

There is a flash yhat may help you. see tsb 18-022-07

 

[nikwave]

There is a flash yhat may help you. see tsb 18-022-07

i changed the ecm not long ago,i would thought it came with all the updated flashes. tomorrow i go by the ex-dealership an see if they can read the ecm and see if that flash is already there or not. thanks Bob.

 

[nikwave]

i changed the ecm not long ago,i would thought it came with all the updated flashes. tomorrow i go by the ex-dealership an see if they can read the ecm and see if that flash is already there or not. thanks Bob.

the exdealership want to charge me $180 to reflash the computer.

 

[TRedwine]

Ok, I have been reading and found that the fan is controlled by the ecm. The fan will come on in the morning sometimes for example today going to work it came on as soon as I cranked the truck and went off after about a 1/4 mile of driving. yesterday going to work it did not come on at all going to work. This was with the a/c off . If I drive around town the fan will come on sometimes and the engine is no where near max temp, also with the a/c off. Do I have a bad fan or a bad ecm or maybe a bad temp sensor that is sending a incorrect temp signal to the fan circuit . Is there a way to test without special tools.
Any help would be greatly welcome.

 

[nikwave]

Ok, I have been reading and found that the fan is controlled by the ecm. The fan will come on in the morning sometimes for example today going to work it came on as soon as I cranked the truck and went off after about a 1/4 mile of driving. yesterday going to work it did not come on at all going to work. This was with the a/c off . If I drive around town the fan will come on sometimes and the engine is no where near max temp, also with the a/c off. Do I have a bad fan or a bad ecm or maybe a bad temp sensor that is sending a incorrect temp signal to the fan circuit . Is there a way to test without special tools.

Any help would be greatly welcome.

mine doesnt come on ,but the fan is still good,i did this test and it engaged correctly. but my truck gets to 215 degrees going uphill,and i wish the fan would kick in sooner.



The first test is to check the gray/pink wire for power with the key on. If you have power, take a jumper wire and ground the brown and orange wire with the connector still attached. Then start the engine and run it at 2000 rpm and see if the fan speed ramps up to full speed after say 5 minutes. You should hear and see it speed up.