When driving Barth II back from N.M. we had plenty of hot water provided by the motor-aid. Since then, I can't seem to get hot water on the last three outings when arriving at a campground. I did a search to try to find an answer on site here, but the only thing I see possible is that we may not be traveling far enough for the motor-aid to heat the hot water properly? Other than winterizing the coach (I blow out all water lines), I have not touched anything that I believe would stop the motor-aid from working as it did on the trip home. Best I have been able to get so far since bringing Barth II home is "barely luke warm" water. Couple of quick questions---
1) How long do you need to run the motor before you have "hot" water?
2) Does the engine temperature need to be at 180-190 degrees for the motor-aid to work properly?
3) Is there anyway to improve the motor-aid hot water heating ability?
We do NOT have motor-aid aux. heat in this coach, so there are no extra switches. Seems the motor-aid hot water works as it did in Barth I, just heats the hot water when motoring down the road. But Barth I would heat the water "hot" on the same trips we have taken so far in Barth II. Anybody got any ideas?

I have a similar system in the Wanderlodge. The engine coolant circulates through a heat exchanger to transfer the engine heat over. Here are some thoughts to ponder.

If you don't have enough water in your hot water tank, the transfer wouldn't take place.

If you aren't at operating temp for enough time, the transfer will not be complete.

If the potable water is really cold, it will take longer to get up to the same temp as the coolant.

If you engine coolant thermostat doesn't get up to temp, it will not circulate into this system.

It is likely tied into the same line as the defroster and heater core, a good place to test for circulation of heated coolant.

There may be a switch that you just aren't aware of.

If your temp gauge on dash reads, say, 180 and you can verify heat to the heater, you might then try to test the line going to the hot water tank coolant feed to check for heat too.

I ruled out a clogged heat exchanger as you said it worked previously, but a partially gunked up heat exchanger could cause it to take a very long time to do an adequate heat exchange.

Sorry to hear your motor has aides!!

I'm not familiar with the actual routing of the lines to the heater but since you "blew out the lines to winterize" I wonder if you have an air bubble trapped in the heat exchanger? It may be the high spot in the system. You might try disconnecting the heater loop temporarily and flush it with a strong flow from hose to purge any trapped air? The flow through the engine may not be fast enough to move the air out. Just a thought.

If you get heat out of you heater, then in almost all cases you will get heat to the water heater. They normally use the same coolant lines for both and this lines are before the engine thermostat.

Check underneath to coach - there's probably at least one, possibly two, cutoff valves (intake and discharge) above the wye connector. Make sure both are fully open.

However, if the campgrounds are less than ~100 miles away, as has been mentioned, there's not enough time to fully heat the tank.

Thanks to all who replied.
Corey-Points taken. Heat exchanger? I thought that the "motor-aid" heating system is nothing more than just lines run from the engine cooling system that circle the hot water tank and the heat from these lines heat the tank therefore heating the water inside.
Steve-When blowing out the coach for the winter, I just do all the fresh water lines/fixtures. (By the way, this way of winterizing your coach has worked well for me since owning a Barth.) I do not do anything with any of the coolant lines. The only time they would be flushed is for coolant system maintenance.
Gary-I have plenty of heat/defrost up front.
Rusty-I'll check for cut off valves. My problem may be the distance I traveled. I will be using the coach for a 200 mile trip (one way) this weekend so I'll see how the hot water is upon arrival.