Got one of
THESE for both the coach and TC, work great. The RV has a little more sophisticated frige so it was easy to hook up the fan to start when the frig is turned on. The truck camper was a little more challenging, had to run the hot lead down the condensate drain to find power, it turns on by clipping it to the fins when I fire up the frig.
No relationship with the seller other than being a happy customer.