1984 electrical help

[slasky]

Does the 1984 logic module turn on the fan when the module goes into limp in mode. If it does what type of signal does it send + or -?

[Turbo_Rampage]

I'm pretty sure it sends a ground signal to the fan relay.. I know my Rampage (SC harness) runs the fan by the LM grounding out the fan relay when it gets to temp, are limp in mode. I would think the fan would come on if you unplugged the CTS, but i have never owned an 84 TD, so i dont know for sure.

http://minimopar.knizefamily.net/fault/code35-1984.html

Hope this helps

[22mopar]

for any car, when in Limp-in, the cooling fan is turned on. this is just part of the fail safe to ensure overheating doesn't occur. now on the method of turn on. there is NO signal sent to the fan!!!. the module applies a ground for the relay. this is done thru a transistor in the module.

[slasky]

I know it turns the relay on which turns the fan on. I jumped the relay and the fan turned on. It made a loud screeching noise because it probably has not been on since 1993. I sprayed some lube on the end and it is quiet for now. I hooked the relay up to power like it says on minimopar and it did not click. There were more terminals than wires going to it so I though something was wrong. I opened up the relay and the coil wires do not go to the right wires. I hook the coil wires up to the battery and it works fine. I figured it was the wrong relay so I looked it up. Sure enough 84 uses a different relay and the one in there is for 85 and up. I used a test light on the signal wire and did not get a ground or positive out of it when I put it in limp mode. Since it does not have AC I guess all that matters is that I get a ground from the fan temp switch in the radiator when it gets to the right temp.

[SwiftTech]

Check pin 18 of the red connector, dark blue with pink tracer wire, that is the signal wire from the LM to the radiator fan relay. I'm not sure if its positive or negative but it should be negative.