Quote Originally Posted by shahzadlateef View Post
Thanks all. I will get sensors changed out and see if that resolves it before buying the test apparatus. I figure that the test apparatus may not catch sensor issues as it completely bypassed the Webasto controller.

Pulled out three sensors and ordered new ones. I know it is not the overheat fuse because it had been shorted. I have included pictures below. There is no inspection detailed enough that will catch something like this. The sensor is $30, so I don’t know why someone will bypass this important feature.

Will let everyone know of the outcome.

Regards, Shahzad Lateef
2003 Marathon H3-45, DS
This is the test box I use. It doesn't bypass the Webasto controller it goes in it's place and allows you to control the system right there at the unit. There is a light that will tell you if your thermostats are bad.

https://www.suremarineservice.com/He.../5011070A.html