92 Dodge Caravan Cooling Fans will not turn on

[bamaboy_1966]

I have a 92 Dodge Caravan, the cooling fans will not turn on. I have jumped wired both fans and they will run. I have replaced the relays and the temp sensor and they still do not turn on. Any ideas

[mcmalloy]

there should be a seperate sensor for the cooling fans, or you might have a broken wire

[RIP]

Your PCM may not be applying the ground to the cooling fan relay coil.

[bamaboy_1966]

I am thinking it is the the engine controller (ecm). I checked the engine codes and it said their is a short in circuit 27. which is the fan relay. so I checked the 60 way connector on the (ecm) pin 31 and their was power. so I am thinking the (ecm) needs to be replaced.

[RIP]

ECM is a generic code for any computer that controls the engine. They're called PCMs on Chryslers. Same same.

Just make sure there's not a wiring problem lurking in the weeds. When you said you changed "the relays" that was the cooling fan relay correct?

[bamaboy_1966]

Yes I replaced the radiator fan relay and the a/c fan relay. When you jump wire both fans and they do come on. When you put the relays back in their is no power going to either fan. When I checked the engine controller(next to the battery) at pin 31 which is the fan relay their was power. Manual says to replace the engine controller if their is power. I have checked the ground wires all of those is fine. I have checked the fusible links, they are also fine. but if their is something I am missing??? I am certainly up for more ideas before I spend some money on something I may or may not need.

[RIP]

I don't have your manual but I'd say power at pin 31 confirms the circuit from the ignition switch through the relay to the PCM is good correct?
I'm not sure there's a safe way to check to see if the PCM itself sets the ground. Sounds like you have checked all you can. Now comes that decision to spend big bucks on a part when you're not 100% sure it will fix it. I've been there and feel your pain. Unfortunately, it can come to that. I'd recommend you first check local junkyards to get the lowest possible price. I would expect less than $100. Then comes Ebay at around $100 -$150. Then the internet sites at around $250. Your dealer, if they can even get one for a 92 would be in the neighborhood of$300 -$500. A dealer PCM would have the latest updates.

I've read once or twice about people jerry rigging a switch to bypass the PCM. Don't recall how but it may be an option.

Just to make sure, the fans aren't coming on either by engine temperature or with the A/C switch correct?

[bamaboy_1966]

Yes, I really dont know what else to do but replace the computer and go from their...I appreciate your help. I will let you know if it worked or not.

[bamaboy_1966]

Originally Posted by RIP

I don't have your manual but I'd say power at pin 31 confirms the circuit from the ignition switch through the relay to the PCM is good correct?
I'm not sure there's a safe way to check to see if the PCM itself sets the ground. Sounds like you have checked all you can. Now comes that decision to spend big bucks on a part when you're not 100% sure it will fix it. I've been there and feel your pain. Unfortunately, it can come to that. I'd recommend you first check local junkyards to get the lowest possible price. I would expect less than $100. Then comes Ebay at around $100 -$150. Then the internet sites at around $250. Your dealer, if they can even get one for a 92 would be in the neighborhood of$300 -$500. A dealer PCM would have the latest updates.

I've read once or twice about people jerry rigging a switch to bypass the PCM. Don't recall how but it may be an option.

Just to make sure, the fans aren't coming on either by engine temperature or with the A/C switch correct?

Well I replaced the Engine control module...did not do a dam thing. the only thing it did was to get the radiator cooling fan relay to click. although the ac fan relay would not click. how can you tell if the engine control module is applying the ground. I am about to loose my mind...lol

[RIP]

Uh boy. You probably already have but if you think everything has been checked the only thing to do is start over. I'm away from my sources right now so can't help beyond that.

[jpb53]

Where did you jump the fan to get it to run?

[BlackDawg]

I have had problems with my '91 Caravan and finally did get it working after replacing the coolant sensor, this was a two connector sensor located near the thermostat. When the engine reaches the proper temp (about the midway point on the gauge). This tells the PCM to ground the wire going to the relay coil turning on the relay. Having the 12volts on this relay with just the ignition on is normal, you need to get the ground from the PCM to complete the path, and this will only be there when the engine reaches the proper temp. If this is not happening, then you may have a broken wire somewhere between the coolent sensor and the PCM or from the PCM to the relay. An alternative way to solve the problem would be to hook up a manuel switch to do the same thing as the PCM is doing, except you would have to watch the temp gauge to flip the switch on when the temp is midway.
The A/C relay should come on shortly after turning on the A/C, if this is not happening then the problem is most likely a broken wire, I suspect from the PCM to the relay.

[bamaboy_1966]

The relay connector.

[bamaboy_1966]

That just it when I turn on the A/C that fine does not come either. jump both cooling fans and they will come on. though the freon is low in the a/c which might cause the A/C fan to not come on. so I am going to put some in it and see if thats it. also I did check the coolant sensor never could get it to go up to 7k-13k so I also am going to replace that. I let you know what I find out. I appreciate your help.