David......Your new and welcome.....to start, you need to tell us what kind of RV you have, Make, Model, Engine, Year etc.
Second, how do you know it's not working. You can't test them while stationary. Most don't operate below 15 mph. What does your transmission say is happening? Does the coach downshift and does your trans window go to 2nd gear or 4th gear.
Don & Mary
2014 Newmar Dutch Star - All Electric - 450 ISL
2016 GMC Canyon 4WD Crew Cab