I am replacing the radiator fan high speed relay on my '08 T&C 3.3L. Why is it an expensive solid state relay, rather than a simple and cheap and reliable contact relay? I don't have a service manual, is the fan speed varied with a PWM type of control? I thought it is just low speed (contract relay) or high speed (solid state relay) radiator fan. There is something odd about the high speed fan control though, because one side is wired to the washer relay control.

 

It's duty cycled. Runs fan from 99% speed down to 30% speed. That's why it's solid state. It's all about energy savings. The fans run only at the speed the engine needs to save gas. A simple contact relay would limit the PCM to a single speed per relay. And by putting the duty cycle function into the relay, they take a load off the PCM. PCM just sends a digital signal requesting a certain fan speed and the relay takes care of the duty cycle.

 

Thanks for the reply, that explains why Chrysler used an expensive part.

Any idea why the washer relay affects the radiator fan high speed circuit, or it's just some weirdness in the circuit naming. One side of the high speed relay control is named "HI SPEED CTRL", but the other side of the control is named "WASHER RLY CTRL".

 

The exported version of the minivan has headlamp washers and that wire is tied together between both relays