Hot water issue

Thank you everyone. Old-Biscuit, I was thinking something in order of this troubleshooting method,your idea of using the PRV in this manner is a great idea. Thanks

great tip!

How many valves on backside of water heater?
1, 2 or 3

3 valve systems (cold inlet/bottom valve, hot outlet/top valve and bypass valve/connects cold/hot water lines.
They typically do not have any check valves.

1 and 2 valve system do have check valves.
Typically the check valve is in hot outlet....inside nipple that is screwed into tank (hot outlet line is then connected to that nipple)

The check valves are cheap plastic plunger/spring/o-ring assembly. The fail and block flow out of water heater.

Sometimes a check valve can be used on cold inlet nipple.

So........
With heater turned off turn off water supply.
Then flip open the Pressure Relief Valve (outside compartment)
CAUTION: WATER CAN BE VERY HOT AND UNDER PRESSURE

With the PRV OPEN turn on water supply
Does water flow out of PRV under pressure?
IF so..cold inlet is OK (allowing water into tank) and problem is with hot outlet
IF water flow doesn't increase.....then cold inlet is problem

Moved from General RV'ing forum.

Check valve installation will vary by coach manufacturer.
Only way to tell is to look in the back of the water heater. Sometimes that doesn't work.
Have you flushed the tank out?