When in need of a hard-to-find heater control cable, I recommend Ray's....he made up an exact duplicate of what I needed & shipped fast for less than $20.00....

http://www.rayeveritt.com/HeaterCables/HeaterCables.html

I have also experianced the same exact problems with dash heat and distribution of the central heat.
Looks like I will have to break into the dash to fix that problem.
On my unit, I have the basement central A/
C which was replaced with an upgrade unit somewhere down the line. When the A/C is running there is very ample air flow thru all vents in the floor (indicating no baffle problems). But when the central heat is on, it performs just as described by Don in Niagara --- just limited flow in the bath and back bedroom --- very little up front, and it uses the same vents as the A/C. I couldn't find any access panels under the coach.
Since I rarely use the coach in really cold weather, I have not persued the problem. But it is strange that my unit seems to have the exact same heating problems as yours.

I'm in the midst of repairing this issue; after getting the roof A/C fixed. on my way home, I noticed hot air out of the dash A/C vents, even though the heat control lever was at minimum.

I found the outer casing had pulled out of its terminal at the dash. J-B Weld cured that, but I still get hot air.

Reflecting back on the operation, the heat control had been stiff, and a couple of times I had to fight it. I suspect the valve bound up, and I broke the butterfly free from the shaft. I'll investigate when I get home (I'm currently in an RV park in Gulfport, MS, awaiting the passage of nasty weather tomorrow).

kevin, make sure the valve is turned on. Mine is next to the pump. sky

Kevin: Has the new booster pump improved your heating system? My schematics show a Red wire with the number 45 as providing power but no mention of a switch. I wonder if it is controlled by the Aux Heat dash switch? My switch for that only has two wires and it seems you would want it on to heat the hot water while in motion.