The first step is to diagnose the cause of the problem. There's three circuits to consider. The first is the coolant temperature sensor for the Engine Computer. That is not the same as the sensor for the dash gauge. The CTS tells the computer the coolant temperature, then the computer turns the fan relay on at around 210 degrees. That's the second circuit. The relay turns on the high-current to the fans. That's the third circuit and the one that usually develops the problems. The fastest way to diagnose this system is to use the Chrysler DRB3 scanner to command the fan to run. That will allow you to see the actual engine temperature to be sure the sensor circuit is working, and you can take voltage measurements in the relay circuit without having to run the engine.
Some people complained that they could actually hear the fan when it turned on. It wasn't very loud but in response the engineers came up with a continuously-variable-speed relay which is another unnecessary computer module and highly prone to failure. If you're going to guess and try random parts, the relay is the best suspect. It has four wires in the plug and usually sat halfway down along the left side of the radiator. There was a service bulletin related to it to check for broken mounting bolts. If they break the relay will seriously overheat. If it's still working it will get hot enough to burn you. It has to be bolted tightly to the body to dissipate the heat.
Friday, April 26th, 2013 AT 11:21 AM