[bearsville]

The fan on my 1999 3.3L Grand Caravan is running after I shut the engine off. I have never had any of my Caravans, K-car, or Pacifica do this. I am about to disconnect a fuse or battery. The service manual points to a number of things for me to look at but right now I am just trying to determine if it is ever going to shut off. Does the 1999 caravan have any normal operating condition where it should do this?

 

[poorboy_616]

Chances are it's the fan controller. Somebody here can reveal more about than I can. My experience lies more the second generation Minivans....

 

[valiant67]

The only way the fan will run on is bad relay. Fan is always off when ignition is off unless the relay failed.

 

[John Wood]

You'll find that fan relay located on the body frame next to the radiator bottom on the driver's side. It is an electronic relay and a bit expensive. If the mounting screws are rusted or the relay is loose from its mounting, it will overheat and eventually fail. The frame where it mounts acts as a heat sink. There is a TSB for this issue. The TSB calls for replacing the relay with a later version and the use of slightly larger stainless steel hex head machine screws to mount the relay.

 

[Bob Lincoln]

The relay fails in a closed mode due to the contacts welding shut inside. This is due to back emf, the inductive voltage from the fan motor winding discharging back into the contacts upon the relay attempting to open. The improved relay probably has an internal diode to block this, the same as the diode built into the A/C compressor clutch connectors. It's funny that they used a diode on the A/C, but not on the fan.

When this gets stuck, you can either unplug the load side of the relay, or unplug the fan motor. Doing the latter, then plugging it back in again, ensures that you can still use the cooling fan. If you plug the welded relay back in, the fan will start again.

 

[ImperialCrown]

This is a 'solid state' relay. No mechanical contacts to stick closed.

 

[bearsville]

Thanks everyone....I took out the fuse to stop the fans last night. When I put it back in this morning the fans started up again. I have a cup of coffee, my serice manual open, and will pull that relay out today. Looks like I might have to wait until Tuesday to get parts unless the guys and NAPA have to work on Labor Day. I just hope it is not the Power Control Module....one of the possibilities the service manual suggests.

 

[Bob Lincoln]

This is a 'solid state' relay. No mechanical contacts to stick closed.

Then it has suffered electrical 'latchup' from the inductive kickback. Same solution, needs a diode to block the energy.

 

[Frank G]

Then it has suffered electrical 'latchup' from the inductive kickback. Same solution, needs a diode to block the energy.

Bob, I respectfully disagree. John Wood's post explains this problem very well, IMO. I believe that relay was engineered with a fail mode as "Always On". I'd rather hear the fans run than hear the engine seize.

 

[Frank G]

Thanks everyone....I took out the fuse to stop the fans last night. When I put it back in this morning the fans started up again. I have a cup of coffee, my serice manual open, and will pull that relay out today. Looks like I might have to wait until Tuesday to get parts unless the guys and NAPA have to work on Labor Day. I just hope it is not the Power Control Module....one of the possibilities the service manual suggests.

You should be able to check if it is the PCM by seeing if the fan relay is getting a trigger voltage with the van off, fuse in place and the fan running...or just pull the plug from the relay under the same conditions and check for voltage at the appropriate pin on the harness end of the plug. That way you won't have the fans running when you do the test.

 

[bearsville]

I replaced the relay just now and that resolved the problem. The new relay came with thermal paste and instructed me to mount it on bare metal. I got out the dremel tool and took care of that. I do not know why but the car had a very difficult time starting after I got everything back together. After a very long and hard start, and some rough running, it smoothed out. I cleard the code and after a full warm up and testing with the AC on it seemed to be cycling properly.

thanks again for all the input. I can't believe I have not been on the forum since 2004! Now to resolve the leaky transmission hoses and then on to the noisy front end on the Pacifica.

 

[jamescurtis]

My relay was mounted under the left headlight. I had to remove the headlight to find it. No information about it in AllData. When I bought the new relay from Chrysler there was a single sheet of instructions explaining where it was located and which screws to use with it. No thermal paste though. It did point out the need to keep the sheet metal around the screw holes flat so a good contact was made between relay and frame.

Apparently the location was changed to help solve the overheating issue. In Canada, at least.

 

[vwdsl]

So, is there no condition under which the fans should run with the switch off? Most other cars I own, the fans will run whether the ignition switch is on or off if the coolant temp is too high. My 2000 Grand Voyager, seems like they will only run with the ign sw "on".

 

[ImperialCrown]

Back in the '80's, the radiator fan used to run to cool the engine compartment for a few minutes after shutdown. Many people never had a car that did that before and were concerned about it running the battery down, etc. Omni/Horizon and K-car comes to mind.
I think with the beginning of EFI and having no more vapor lock or fuel-boiling-out-of-the-carburetor issues, the need for engine compartment cooldown dropped off. I don't think that any Chrysler product does this any more.

 

[John Wood]

Your last sentence is correct. When the ignition is off, the fans should stop. I'm not sure about the newest models, but Chrysler did have a system back in the 80's (2.2 carbed FWD cars) that had a thermal switch that kept power to the fans until the radiator cooled to a certain point. There were a lot of failures of that switch and I remember working on a few cars that had the thermal switch completely removed.

Regarding other car manufacturers, I too have witnessed several vehicles with the fans still running for a few minutes after the owner removed the keys and walked away.

 

[Bob Lincoln]

It must have been early 1980s cars, and maybe only with carburetors. My 84 Daytona Turbo Z only runs the fan with ignition on. The underhood decal on the radiator, and the owner's manual both mention this.

 

[John Wood]

Only carb cars and as IC stated, it was there to help reduce vapor lock (boiling fuel) in the fuel lines and carburettor float bowl.

 

[valiant67]

So, is there no condition under which the fans should run with the switch off? Most other cars I own, the fans will run whether the ignition switch is on or off if the coolant temp is too high. My 2000 Grand Voyager, seems like they will only run with the ign sw "on".

The vast majority of Chrysler products shut the fan off with the ignition off. I've never had one that behaved differently.

 

[chuzz]

That same thing happened to my 99 GC a couple of weeks ago. My son and daughter went to Walmart and when they got home, they were freaking out about it. I pulled the fuse first and waited a couple of minutes and then stuck it back in and they came back on, so I pulled the realy and swapped it with the one for the cigaretter lighter since I'm a non-smoker and don't use it anyway. That did the trick, but I did have to clear the code that popped up about the low cooling fan speed. Easy, peasy!