Date:         Sun, 22 Mar 2009 08:13:54 -0400
Reply-To:     email99 <email99@BELLSOUTH.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         email99 <email99@BELLSOUTH.NET>
Subject:      Improving the performance of the Vanagon air conditioning fan and
              saving the switch
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Poor air distribution is a significant problem with the rear mounted
Vanagon air conditioning systems.  After the thermostat/evaporator
fan/condenser magnetic clutch switch on my '86 Westfalia failed a second
time I decided to add some load handling relays in the rear to handle
the high amp fan load that this switch was trying to handle.  I measured
the voltage available at the fan in the evaporator housing and found
something like 9.5 volts, significantly less than the battery 13.4
volts.  This voltage drop was the result of a weak switch and long,
under sized wires and resulted in decreased fan performance.  To correct
this I added a 12 gauge wire (with an inline fuse) from the Distribution
box in the engine compartment to a rack of four standard load reduction
relays located in air conditioning housing to control the power to the
AC fan motor.  I also ran a 12 gauge ground wire from the fan motor to
the chassis ground near by.  These relays were controlled by the three
wires from the dash air condition fan switch.  Why did I use FOUR relays
for only THREE speeds?  I found that after running the fan on high speed
the high speed relay would overheat and stick on.  Rather than buy a
high capacity relay I just wired an available second relay in parallel
to the sticking relay to help carry the load and fix the sticking
problem.  The fan motor now operates much closer to its rated 12 volts
on all three speeds although I don't remember exactly what I measured.

While I was doing this I also wired in a load reduction relay to carry
the current to the compressor magnetic clutch.  This might actually be
redundant but I did it anyway since this would definitely supply full
voltage to the clutch.

The result of this small wiring exercise is that the low fan speed is
now equivalent to the old medium speed and the high fan speed is much
more powerful than before, easily forcing air all the way to the front
seats.  I very seldom find any use for high as it blows on my neck while
I'm driving.

This very simple modification that significantly increases the
performance of the air conditioning system of the Vanagon and also
insures that the very expensive Westfalia AC fan/thermostat switch (P/N
175 272 327, ~$246 from a list vendor) will last a long, long time
without burning out.

A year before I did this relay modification I installed a second AC
evaporator in the dash and a couple of years ago I added a second
condenser under the bottom of the bus behind the gas tank.  Each of
these were significant in improving the AC performance to a level that
currently entirely adequate and comfortable.  If I were doing this over
again I would definitely start with the relay modification first because
this prevents the self destruction of the fan switch and improves the
standard Vanagon air conditioning system from a very poor performer to
an OK performer.  The relay modification is also the cheapest of the three.

I've written about these modifications on both the Vanagon list and the
SubaruVanagon Yahoo list.

I hope this helps someone.

Ed