[QUOTE=Juiceb0x1968;3105294 But the sensor i'm not so sure about. I read it is behind the alternator, so I hope I will find it. Just to be clear....when I find it, I unplug it and take the end coming from the wiring harness and put a paperclip across it? If the fan stops, then the sensor is buggered? Is that right? Also, I just switch relays, and if the one I replace it with stops the fan, then that means the relay is bad? Finally, how do I test a thermostat? Or should I just replace it regardless.

Also, there is coolant in the system. That questionable mechanic filled it up, and there has been no coolant leaking anywhere, so I assume that means the system is tight. I was also talking about the fan right behind the radiator. It constantly runs, and then every couple of minutes, some pulley right behind it will wind up for a few seconds and then stop again. I havent checked the steering or transmission fluid, but I will. The fan inside the cabin blows strong....just cool air though. All the fan speeds work, but I havent checked to see what happens when I change the where the air comes out from...but I will.[/QUOTE]

Just because you don't see it leaking doesn't mean it's not leaking, or that there's still coolant in the system.

Thermostat can't be checked.

Temp sensor is behind the alternator, yes. May or may not be a PITA to get to. I can hardly see it on my 3.9.

Are you talking about the electric fan attached to the radiator, or the clutch fan that is attached to the water pump/engine? We're all assuming you mean the electric, as the mechanical is always spinning.

Also, that pulley you hear engaging is the AC pulley, if it's the top right one with a couple of silver aluminum pipes going to it. Your AC is on, which would cause the electric fan to be on, and the system to blow cold air.

 

To add to what Magnet posted, your a/c will run when in defrost (and so will the fan).

 

OK. I will check the colant again. This may sound stupid, but what is the best way to check? Just take the radiator cap off when its cold and look? Do I let it warm up and then take cap off while its running? If you check the over flow bottle and it has coolant in it, does that mean the coolant level is fine? Also, if the A/C is on, but the A/C is not selected in the cabin, what would cause that, and how do I fix it? And just to be clear, the fan I am talking about is the electrical radiator fan that is right behind the radiator with a shroud around it. Thanks again everybody.

 

Turn the HVAC controls to "off." The a/c (and the fan) should not be running unless the engine is very hot.

Checking the coolant in the overflow tank is the proper method. The level varies as the engine warms up/cools down. As it cools it draws antifreeze into the cooling system to maintain the level.

Check for a radiator fan relay. It may have failed, welded shut, so that it's running all the time.

 

but if the fan relay welded shut (which I have seen happen, especially on a high amp draw like the fan), it wouldn't be cycling the AC compressor. Now, if the A/C system relay welded shut.....?

also, right/wrong/indifferent, my way of checking coolant level is just removing the cap when cold. It will push coolant out when hot, so as long as it's full when cold, it should be full when hot. Our trucks are unique in having mostly tankless radiators and having the cap on the hose.

 

Juiceb0x1968

Get the free service manual and the Dakota Owners Manual here on this forum

https://dodgeforum.com/forum/2nd-gen-dakota/70233-2000-factory-service-manual-pfd-download.html

Get some reading in Pal

 

Thanks Dakaz. That will help a lot. Plan on digging in more starting Friday. Appreciate everyone's help so far.