John, Be sure you have enough water in the cooling system first. If not, this may be your problem. Without enough, the heater core will not get warm, let alone hot. This may sound simple, but check this first and eliminate it as your root problem. Mark vin2602 --- In dmcnews@xxxx, deloreanss@xxxx wrote: > I am having a mysterious problem with my heater. The problem is that there is > no heat. I am speculating that it could be the hot water valve that allows > the hot water to flow into the heater core, but I do not know how to test > this theory. I don't think that it could be the heater core b/c I would think > that would be evidenced by a leak or something. The only other idea I have is > that the vacuum actuator that opens the heater flap isn't working, but I > would think that would be the least likely scenario. Does anyone have any > ideas? > > Thanks, > John Weaver > ETDOC > RED DMC #10527 > > > > [Non-text portions of this message have been removed]