Date: Sat, 16 Sep 2000 15:57:25 PDT
Reply-To: Brian Sassone <bsassone@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Brian Sassone <bsassone@HOTMAIL.COM>
Subject: Refrigerator Self Discovery
Content-Type: text/plain; format=flowed
After trying repeatedly to light my 'fridge, I bit the bullet and removed
it. Here is what I found:
There is a small sealed burn chamber on the bottom left of the fridge. This
is what the "mystery tube" that can be seen under the fridge runs up to.
This is actually an access port that comes up inside-bottom of the burn
chamber and can be used to blow ash and dirt out of the chamber up through
the flu using an air compressor. Mine was so clogged, I had to rod it out
with a piece of wire. I would guess this is just a quick and dirty way to
clean the flame spreader as it is hard to see how you could blow all the
crap that I found in there out the flu (maybe with a very high pressure
compressor.)
Inside the burn chamber there is a small gas jet that allows gas to flow
through the flame spreader which is actually a small tube with slits. There
is a small sensor that detects a flame and shuts off the main gas flow to
prevent gas leaks if the pilot blows out. This is bypassed while you hold
the button in for starting. On mine, there is also a wire that runs to the
light on the cabinet panel to show that the burner is lit. There is also
the contact that supplies spark from the peizo electric starter that is
triggered when you push the air pump all the way in.
There is a window in the side of the chamber through which you can clearly
see the flame when it is lit. Unfortunately, it is in back of the 'fridge,
and the port inside left of the fridge (which is actually a small diameter
solid plexi-glass light conduit) is not directly aligned in front of the
window to allow a reliable sight into the burn chamber. I realigned mine as
close as I could, and still can not see the flame through it when lit. I
solved the problem by mounting a small mirror at an angle under the fridge.
Now I can see the flame directly (well - indirectly I guess is more
technically correct. :-)
Using a mirror allows you to judge the color of your flame more accuratey.
It should be blue indicating a strong clean burn. Mine was yellow. So, I
removed the gas jet and repeatedly soaked it in alcohol and blew it out with
air. It is too small a jet to poke with a wire without damaging it, so just
use compressed air (or blow really hard like I did. :-)
I also cleaned the flame sensor tip with a brass wire brush as it was
heavily carbonized. The sensor was apparently working, but the light was
glowing so dimly on my panel, I couldn't tell at first! I'm not sure
whether obtaining a stronger burn on cleaning the sensor, or both, helped,
but the light glows strong enough now to be seen in daylight. It is still
dimmer than the other lights on the panel, so be sure to check it closely.
When you shut the gas off, you can watch the light slowly fade as the temp
drops.
The flu vent actually has two pipes running to it. One runs from the burn
chamber along side the heat exchange portion of the cooling system (OK, so I
don't remember much of my thermo-dynamics except for pv=nrt. :-) This is
alternately heated by one of two heating elements, one for the DC and one
for the AC. The second pipe that runs to the flu vent (and is hidden from
direct view from the outside)s is the fresh air intake. When the flame is
lit, a little convection process keeps it alive.
Before it is lit, the air pump must be used to get fresh air into the burn
chamber. There is a small one-way check valve directly behind the pump,
then a steel tube that runs down through the main fresh air pipe to an
outlet right at the burn chamber. Now, the Bently manual shows a
modification to get better air flow. It involves removing the pump and
disassembling it to add a small O-ring washer to the pump shaft (presumably
to get a better seal and thus create more air flow). The mod also involves
drilling out the air hole exit from the pump to 9/64 as well as replacing
the one-way check valve and hose with a new check valve (VW part number 055
131 101) also drilled out to 9/64 and a larger diameter hose - 5/32 ID
(approx. 3/16). I called VW and found that they had 5 of those little
valves in the LA distribution hub (amazing to me) and that they were $14.95
(not so amazing). I found a similar check valve for $2.95 at my local
aquarium store. They are used to install between the air pump and fish tank
to keep water from back flowing to your pump. Anyway, it is not as large a
diameter as 9/64 and I never got to test it since I decided not to mod the
pump after I found that I could light the burner reliably without it. (I
always follow the "If it ain't broke, don't fix it" adage to a tee.)
I noted a few other things while I was "inside". First, there is a small
cooling fan that runs off a thermoswitch connected to the cooling fins on
the heat-exchanger. This runs off the battery, and is unaffected by the
switch on the front of the fridge. Although, I think the fridge relay
(behind the driver's seat) shuts off power to the fridge when the engine
isn't running (although I could be wrong since I have not confirmed this but
that is the way the schematic reads to me.) Also, to note, the thermostat
controlled by the min/max knob on the front of the fridge only works on gas
or AC.
Brian
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