Chrysler Repair: 94 Caravan: radiator fan keeps running after shutoff, square boxes, radiator fan

Question
Oh wise one...........thank you for responding!
My engine is a size 3.3L
There is a black plastic box sitting on the fender above the battery.


Answer
Hi Bridget,
Inside the box there are three relays (of a total of 9, these are the black small square boxes that switch power on and off when told to do so) that are involved in sending electric power to the fan motor. The motor has 2 speeds, so there is a relay for low speed and for high speed operation, and additionally there is a relay for "grounding" the high speed relay circuit. One of those three relays is probably defective in that it fails to open the switch when the ignition is turned off. The internal contacts inside the relay box are probably fused together due to overheating.
What I would do is reconnect the battery so that the fan starts again (if for some reason it has spontaneously disconnected, e.g. the relay switch has opened after it cooled down, then you will need to wait until it does this 'trick' again to solve it) and the try removing the relays one at a time. Simply pull them straight up out of their sockets. Start with the rad fan lo relay. If that stops the fan then that is the bad relay. If that doesn't stop it, then pull the rad fan hi and the rad fan gnd relays which should stop it. But you need then to figure out if it is the gnd or the hi that is the bad one. Try using the rad fan lo relay (which you know is good if when you pulled it it didn't stop the fan) and try using it with each of the other relays in the hi and the gnd sockets. One or the other of those two relay will then reveal itself as the bad relay. Before you start substititing however do check to make sure that the three relays all have the same part number, so as to be interchangeable. If you think you have identified which relay is causing the fan to continue to run you can either replace it or perhaps open the relay and pry gently on the switch points to open them and then file them clean so they won't stick together.
That is my initial suggestion. In thery there could be a short circuit or malfunction of the computer that controls the relays, but in all likelihood one of the three relays is bad. The location of the relays will either be shown on the lid of the box or labelled on the circuit board into which they are plugged.
Let me know how this works out. Thanks for the compliment, which I hope I have met.
Roland