Here's something I posted last year.  Gee... sure would be nice if someone
added some of these things to the vanagon web page....

>From: "Brian Sassone" <bsassone@hotmail.com>
>To: bsassone@hotmail.com
>Subject: Refrigerator Self Discovery
>Date: Sat, 16 Sep 2000 15:57:52 PDT
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>16 Sep 2000 22:57:52 GMT
>
>
>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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