trying things is the way to do it. it will be obvious what is what then. i beleive michael has one set that is for the hot water heater only and the others are for the front, bed and bay heaters. on the one that has the hot water heater on it, it should likely not have a 12v valve/pump with it. on michaels, it is just a straight loop with out any controls or booster pump. since the other lines go clear to the front, it has a booster pump on it. when you turn the heat/cold lever on the dash heater/ac panel to the right just a little you will hear a slight click. that click is triggering a micrswitch that michael referred to. this was added to the panel by newell. it turns on the valve and booster pump to let coolant up front and boost it. on mine i have that pump/valve on top of the frame rail on the drivers side of the engine compartment and is in plain sight. some have that pump as a return booster instead and it is behind the dash air plenum in front bay where the genny blower is behind the panel on the rt side.
to get the heaters to get coolant flowing through them like michael said, you have to have that lever on the dash unit to the right just enough to hear that click (usually just a little), then push the heat button. it takes both to get it to activiate that pump/valve. the pump and valve are wired together so both are either on or off.
there are a bunch of "Y"'s in the coolant lies to allow coolant flow if any one of the units gets plugged. these lines congregate in one of the middle bays usually in front of the water bay in the middle.
since there are so may variations of all these things, yours may be like this or slightly different. the concept is the same, it is just where the booster pump and valve is and if there are solenoide valves on each line or or not like dave has.
i ended up tracing them all out and marking them with numbers and letters.
tom
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