Another very big reason for low heat is leaks.  IF the system is not holding
pressure, sutch as a bad cap., the output of the heater will be low.

Mark Drillock wrote:

> 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
>>
>
>