I'm not sure why RV folks still spend so much time and money on a system designed to solve a problem that is about as uncomplicated as plugging in a hair dryer. That is exactly what I've been doing for over a decade of winters now.
I was looking for that chinese GSM switch - do you have a link and where you get the cell service for it?
I looked all over my engine for where I could put the heater strip. The bottom is no good - it is where the air comes in? I found this spot on the back right corner; it isn't totally flat, but I think the heaters are flexible when glued on?
The pics posted above must have been on a slightly different 390 casing; mine isn't totally flat where the previous example was all flat here.
I thought one of the vendors would have an install pick of the right/best place but can't find a 390 heater strip pic that looks like what I have.
Is that a 390-A? On the RV14 it is a 390-C. My 390-C doesn't have that long flat spot - there is a bend there of about 30 degrees in the middle of the area. I talked to Reiff and they confirmed; said that my best bet was to just use the cylinder heater and get the oil warmer that way.