Re: Rear Heat Exchanger 1972 Squareback

[Jim Adney <jadney@vwtype3.org>]

Forwarded to the type 3 list: 

On 17 Aug 2007 at 7:59, Mike Perholtz wrote:

> I am new to restoring VW aircooled, and have been focusing on the heating
> system for the last several weeks.  I recently came across a post at
> type3.org where you talked about the rear heat exchanger.  My question is,
> what does the rear heat exchanger do?  It seems apparent that the front heat
> exchangers deliver heat to the cabin, but the schematics from the owners manual
> almost infer that the rear heat exchange filters engine heat so that fresh
> (unheated air) can be delivered to the cabin?  Just a guess, but any
> clarification is GREATLY appreciated.

All 4 of the heat exchangers heat air for the cabin. The fresh air is pumped 
first into the rear exchangers and then into the front exchangers. The air 
picks up some heat from each one, but the rear ones are smaller so the heat 
contribution from them is also smaller. You can think of the rear exchangers as 
preheaters.

Left side heated air and right side heated air don't mix until they enter the 
cabin (on the left and right sides, respectively.)

It may be instructive to examine your engine closely, after studying the 
manual, to follow the air flow path. The air originally comes out of the fan 
housing thru 180 deg bent ducts on each side. From there you can follow it thru 
the heat exchangers.


-- 
Jim Adney
jadney@vwtype3.org
Madison, WI USA

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
List info at http://www.vwtype3.org/list | mailto:gregm@vwtype3.org
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~