On my 1988 C27 I changed the element this spring and I am able to produce hot water hooked up to shore power. So the 110 side of the water heater seems fine. The coolant lines, both the IN and OUT from motor to the exchanger on the tank are warm to the touch but the exchanger itself is not warm. I am able to slide the exchanger out of its sleeve in the tank to feel the temp of the exchanger. It's like the coolant stops at the point where it enters the exchanger and it is not completing the loop. The engine is operating at 160 degrees and the tank worked fine last fall. I did not open the fresh water cooling side of the engine at all. HELP.... Thanks.... SGL