Thor Tuscany - water is hot everywhere but the shower!

I'm betting on debris in the water line in the shower. Calcium deposits.

Your cold water is mixing with the hot water at the valve (retired contractor), or your temperature limit was set incorrectly. If your valve has a temperature limit was set incorrectly, you can Google the manufactures installation instructions and set it where you want. If the cold water is mixing with the hot water....you have to trace down where that is taking place.

Sounds like you have the water heater bypassed for winterizing. Check you winter bypass valves.

I have a 2018 Tuscany 42GX. Thor has been good at honoring warranty claims by independent RV repair facilities for me. I had a mobile tech come out to fix a leak on my shower mixing valve last spring. Thor reimbursed me 100%.

Take it back to the dealer.

This is one of those problems that we would like to know how it was fixed because there are more and more tankless systems being supplied with new rigs and some conversions.
I have a bias against them for RV use unless hooked up to the campground sewer system and even then I think they are not good for RV's (propane and water use, etc.) But that's just me.
If you like yours I'm happy for you.

Tankless water heaters require a certain minimum flow rate to turn on and stay on. Try opening the hot water in the bathroom sink about a quarter of the way, and with that flowing turn on the shower.
If it is hot and stays that way you may want a higher flow showerhead.

First question: Is it still under warranty? If yes, let them fix it, otherwise you might compromise the warranty. If no, then google is your friend. You tube videos on mixing valves. Not a real difficult job, depending on your skill set.....Dennis

DFord wrote:
I have no idea what kind of mixing valve you have on your shower but I'd suspect some debris in the line leading to the how water side. The easiest way I know of to make sure would be to drain the pressure on your system and remove the valve for inspection. Once the valve is removed, you could put a plug in the cold water line and a hose on the hot water side and pressurize the system and see what kind of flow is available to the shower. If you get a full stream with plenty of pressure, the problem is in the mixing valve and it would need to be backflushed, disassembled for inspection or replaced.

I agree it is very likely a mixing valve problem. Not only could it be debris in the lines it could also be the valve itself has a defective anti- scald component. Nothing special about RV plumbing, so any plumber should be able to fix the issue if you aren't comfortable doing it.

Sometimes the external shower causes hot water issues, but that usually affects the hot water in the entire coach and not just the shower. But still I would make sure the outside shower is not at fault.

Turn the outside shower on for hot and see if you get hot water there. Then make sure to turn off both the hot and cold knobs. As a bonus you can also use a Phillips head screwdriver and switch the knobs to the correct sides while you are out there.

Use flat piece of metal (little flat blade screwdriver, a butter knife, a nail file etc) to pop the center caps out of the shower knobs. Then use the Phillips screwdriver to remove the center screw and pull the knobs off and swap them.