if your dash heat is somewhat lacking in output, and you have a motor aide water heater, you may have a valve that you need to close to get maximum heat out of dash system. On my ORED the valve was accessable thru a small porthole in the cabinet below the sink. Tag indicated to "close valve for max dash heat". As near as I can tell, my heater appears to be original, service records showed It had the gas valve replaced.
Yes, a common (and excellent) feature on Fortravels all across the models and years.
And you need to open this valve if you are changing your engine coolant along with having the dash heat control all the way up. I too have the original water heater, keeping an eye on it though.
Yes, when changing coolant, both motor-aid valve and dash heater valve need to open.
There may also be a additional pump that will push more heated water forward, on my U300 I have a dash switch that says aux pump. on the driver's side in the engine compartment on the frame this pump is mounted and takes water out of the block and pushes water through the system.
This is it. ^.^d
My dash heat aux pump was DOA when I bought the coach in 2012. I never really needed it in this climate here but wanted to have it working when traveling in cold country. I replaced it with a Bergstrum 12v Inlet Booster Pump Assy - Bluebird 10034148 bergstrum 12v inlet booster pump assy | eBay (https://www.ebay.com/sch/i.html?_dkr=1&iconV2Request=true&_blrs=recall_filtering&_ssn=excessinc&_sacat=184670&store_name=excessincorporated&_oac=1&_nkw=bergstrum%2012v%20inlet%20booster%20pump%20assy)
Fortunately it came with mounting bracket. I had to drill out the holes to mount it but it fit in there just like the original. Lost some coolant but replaced it. You're right Andy, it makes a big difference!.
Jerry