Great info on how to check the coolant plug!
Yes, I do believe sometime around my year they switched to having the ECM do the controlling of the fan speed.
Originally Posted by CountryFit
When I worked on our system, the wires from the sensor were to the controller directly, granted our coach was 8 years older, things could have been changed on yours. What I would do if I were in your shoes, I would take the sensor out, dip it into a pot of controllable hot water and measure the resistance. You should see three distinguishable resistances in the vicinity of infinite, 2.5 ohms and 0 ohm between the two poles on the sensor when the water temp changes, if it's any good.