Found an empty fuse receptacle

[jimbobway47]

Still finding new things on my 2018 Forza 38W. I read in other posts how the block heater was plugged in to a switched outlet. I found it, on the electrical schematics, located in the compartment containing the shore power cable and the automatic transfer switch. While at the vehicle I found the plug and it was plugged in, which is what I wanted to verify. While looking around the compartment, whose door also covers the DEF tank, i noticed an empty fuse holder. It is on the partition between the shore power compartment and the DEF tank at the top of the partition There is a label stating '20 A' and molded instructions on how to remove the fuse. The terminals are exposed on the DEF tank side of the partition and a meter showed 13.8 volts on one terminal at 0 volts on the other. I have been unable to locate this fuse on the electrical diagrams but two of them are not accessible on the website (Error 404 - not found) and it also is not mentioned in the owners manual. I am the second owner of this RV and assume the fuse was removed by the previous owner for some reason. There is also a tethered plub that would cover the fuse holder if there was no fuse present. Can't think of anything on 12V that is not operational. Does anyone have an idea what this is for? I may have to call Winnebago or paste this thread into a service request email on the website.

[Winterbagoal]

DEF tank heater, maybe? 20A might be enough for a heating element. Why it was removed would then be the mystery. Just guessing, obviously.

[jimbobway47]

Looks like added wires rather than original Freightliner wiring. I would expect the DEF heater to be part of the chassis wiring. I will look for a fuse labeled DEF heater and also take a picture. I will try to trace the wiring also but it looked like it went into a harness. The location is close enough that it could be DEF heater though, so I will try on the Freightliner website to see if I can find it there. It is right next to the automatic transfer switch. It is also strange that there is a tethered cover for the fuse holder. Almost like it would not always be in place and when not in place you would have a dust cover.

[Winterbagoal]

Good counter points. If it's DEF related, it should be on the FL chassis wiring diagrams, unless WGO had to move the DEF tank and do some wiring reruns to supply 12V (I assume?) power to the DEF heater. Which leads me to "why is it missing"? The cover might be to protect it from weather/water/slush/snow, although how any of that would get inside the compartment doesn't make sense, either.
Again, all just wild guesses.

[jimbobway47]

Into the DTNA wiring diagrams now and there are a lot of them. Another factor is that one side of the fuse holder was hot (13.8v) with the ignition off so I think that eliminates DEF heating. I have a wire tracing tool and I will take it to RV tomorrow and also take pictures.

[jimbobway47]

More info and some pics. I am leaning towards thinking this fuse is for the optional tank heaters. I have a several cable locating tools but the one for telephone wiring did not work so I am thinking the resistance to ground must be low, drowning out the tone generator. This tool works best on wires that are not terminated. I have a second tool and it puts RF energy on the connected wiring. The wire from the fuse holder goes forward towards the waste tanks and i got a strong signal when i put the sensing wand up near the tanks. This picture shows the compartment containing the fuse holder:

This image shows the fuse holder just inside the compartment, next to the automatic transfer switch:

This image show the other side of the partition and the coil of wire with the tie wraps goes to the back of the fuse holder. The black wire goes through the wall towards the back, where the chassis battery and solenoids are located. The White wire goes into a conduit going forward towards the tanks:


Not sure while but these images may be rotated 90 degrees. My first attempt at adding pictures. If this was an option added by Winnebago it should be on some drawing or maybe an email to support will get an answer. I need the insert that holds the fuse. It does make sense that you would take this out in the summer and hence the dust cover.

[Winterbagoal]

If it's for tank heaters and you don't have/use them, that might make sense. I'd ask Winnebago.