Your problem is likely not the heater, the problem is likely the
thermostat for the engine. To put it simply, your bad thermostat is
allowing too much hot coolant to flow to the main radiator and then not
enough heat is left for the heater. Replace your bad thermostat and your
heater will work properly again.

Mark

Andy Highland wrote:

> I've been using my van (1990 Westfalia) in sub 40 F temperatures for
> the first time. When I'm at freeway speeds, the heater is blowing
> cold air. When I close the floor vents, (3rd lever pushed to the
> right) the air gets a little warmer, but not by much. Basically, the
> heat coming out is totally inadequate, but only when going fast in
> cold weather. In more moderate temps, or when I'm on city streets it
> seems OK. So is my front heater broken, or is this how other people's
> vans work? I find it hard to believe that people up north could live
> with such a pathetic heater.
>
> Thanks,
> andy
>