Where is h2o heater pump switch?

[ttomas]

I want to add some auxiliary heaters to the engine water lines. eventually I will put in the webesto but for now I am just installing the water lines, thermostats and heat exchangers. I took out all but the defroster from the original system. I can not figure how to turn on the booster pump.  Where is the switch?    and does anyone have any suggestions of any kind. Thanks again. Tomas                                                                          Also I would like to again thank this board for all of your help. I can not say enough good things about you guys.

[ttomas]

I forgot to mention that I am building an MC9

[RJ]

Thomas -

No separate switch for the booster pump - it's controlled by the OEM HVAC thermostats, IIRC.  When the "Heat On" lamp on the dash lights, the booster pump runs.

You need the electrical schematic for your coach to trace the wiring properly.

FWIW & HTH. . .

[Tony LEE]

MC8 had no booster pump so presumably this was an enhancement on the later MC9

[gumpy]

My 9 didn't have one, either, but I've found the heat light on the dash is controlled by the sensor in the tunnel (front bay) and the relay in the front electrical compartment that's tied in with the temp reostat and is supposed to control the temp in the coach.

[RJ]

OOOOPS!!!!

Sorry, troops, had a little too much Pepsi.   

Was thinkin' GMC, not MCI. . .

[Tony LEE]

There are also manual gate valves in the engine compartment - one near the starter motor and one up high.
The original control valve - operated as described by gumpy, is located behind the curved panel in the front bay and I think it is normally open and must be powered up to close.