Webasto

[Russ]

As new owners, we are working thru the various systems and correcting existing deficiencies etc and the Webasto has always been a problem reportedly so we are into it now but just a simple plumbing problem. The unit itself was newly installed at Prevost in Vancouver May 2017 and the system (DBW2010) works great but the coach history reveals ongoing no heat in aft heat exchanger. This does not have a preheat engine circuit oddly enough. One loop runs fwd to the very front t-ed off to the galley and returns, the other t's off that outbound run on the way fwd and feeds down to both hot water tanks and the return comes back up and to the bath/bedroom exchanger....the one in question. It's exit T's into the common return line. That heat exchanger has zero flow. Removed it, flushed out, no issues, re and re and re and burp and re and burp and sounds like a workout program,,,decided the T on the return was back pressuring the inlet coming from the hot water tanks and halting flow with equal pressure. At some cost in skin loss and twisted fingers, swapped the T for a branch type Y thinking the exit line now blending (not T'ing ) with the suction flow of the return line would pick up the imbalance. Wrong, still no flow...return from hot water tanks is hot right up to a foot away from the exchanger and when the system shuts down, the return Y branch heats up via radiation from the hot coolant, otherwise in and out are cool. Thinking of a boost pump coming up from the hot water loop? Burp hot water tank loop? Weird since it is simple flow but I am clearly seeing trees out there. We live in the woods but there is no forest in sight. Any revelations or hey stupid, on that item appreciated. No doubt others must have seen this as it is plumbed exactly as per the Marathon layout and appears original. There does not appear to be a remote circ pump that I can locate. The Webasto in-unit circ pump may be a bit shy on output to handle those loops? Cannot isolate the hot water tanks loop as a test either, as that is where the inlet flow to that last exchanger comes from. It is a pretty simple system.

There is the standard boost circ pump in the engine coolant/heating circuit to increase flow to the driver area, all fixed and working as it should but not part of the webastard system.

Russ, 92 Xl 40 Marathon