A few years ago I had an 83 1/2 which had the same problem. We had
some cold winters here in the early 90's and I used a very old
fashioned solution - cut out a piece of cardboard that covered about
half (the lower half if I remember correctly) of the front grille
area and left it there as long as the cold spell lasted.  The van
heated up just fine. Overheating light did not come on, no ill effect
on the engine that I know of.

Steve in Chicago

> Date:    Wed, 29 Nov 2006 12:06:00 -0900
> From:    Mark Tuovinen <mst@AK.NET>
> Subject: Re: Front heater: low heat at highway speed
>
> I sympathize with you on this issue, only it has been sub zero here
> lately.  My 87 Syncro GL has been less than generous with the heat
> making for a cold ride to work and even colder one home.  As Mark
> Drillock has already suggested start with replacing the thermostat
> and see how that helps.  I am going to do mine this weekend now
> that is has warmed up to 15F.  Someone recently posted about
> building a partition behind the front seats and using ducting to
> get heat from the rear heater to the front.  I half considered this
> but thought that the kids might complain if I took their heat away.:>)
>
> Mark in AK
>
> ----- Original Message -----
> From: Andy Highland <andy@420.AM>
> Date: Tuesday, November 28, 2006 11:55 pm
> Subject: Front heater: low heat at highway speed
> To: vanagon@GERRY.VANAGON.COM
>
>
>> 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
>>
>>
>
>