[77newell]

The booster pump and solenoid valve are operating fine My coach is set so both open when the heat lever is at about 50% or above. Below 50% there is no hot water flow at all to the front heater core. All the fans are working. I'm just wondering why, independent of vehicle speed, the temperature of the air coming out of the vents, with the lever full to the right for heat, rises when engine is at idle and lowers after a delay when the engine speed rises. I'm guessing, and just guessing, that the engine pump and the booster pump are fighting each other with the booster pump winning when the engine pump is at idle engine speed and the engine pump cancels out the booster pressure when the engine is revved. This could explain the pattern of symptoms I'm seeing and is why I asked for the location of the valve on the engine to which the inlet of the pump is connected. It would helpful to know where both ends of the dash heating circuit are attached to the engine but the return line will not be as obvious as the line connected to the booster pump inlet which is why I only asked for that one.

If it turns out the booster is implemented incorrectly it would not be a first for my coach. The backflow preventer on my hose bib in the water compartment was backwards so it prevented any water from flowing. The plumbing in our coaches is incredibly complicated and mistakes are not entirely unexpected.