Hot water
OK...let's break this down to elements:
1. No water flow of any temperature from any hot water faucet.
2. Full flow from all cold water faucets.
I'm not sure how the valving is set up on your rig, but I'd want to make sure that you have water going IN to your water heater. If you don't, and it's an electric one, you may end up replacing a burned out element.
3. With a bare hand, feel the pipes attached to the heater. One of them should feel cool to the touch (water inlet pipe) and the other should be warm/hot to the touch (water outlet pipe).
If the inlet pipe is cool, but the outlet pipe is NOT warm (assuming that you have power to the heater, and the element is not yet burned out), the blockage is most probably inside the heater itself, assuming that water is flowing INTO the heater. You can open the drain on the heater to confirm that water is going in.
If the outlet pipe is warm/hot, you are heating water, and it is TRYING to go to the faucets.
If this is the case, you will simply have to trace from that point to the hot water faucet located nearest the heater. Sometimes this will be the "auxiliary shower" located on the outside of the coach. If there is no water flow at that hot faucet, the blockage is between the heater and that point.
About the only situation I can think of that wouldn't be covered by these scenarios would be if you had a separate water pump for the hot and cold sides, and that pump was out.
I've never seen that, and in this case, you would still have water flow from both hot and cold sides when you are hooked up to a pressurized external water supply.
Bob