Date:         Fri, 24 Mar 2006 15:59:31 -0500
Reply-To:     Roger Sisler <rogersisler2000@YAHOO.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Roger Sisler <rogersisler2000@YAHOO.COM>
Subject:      Re: yet another fridge question (ok you experts)...

I havent been able to find your origional post. Blockage in the ammonia
circut is rare.  I recently read a book on this ,and the author says that
he has seen it maybe once in his time as a mechanic.Check to see that the
110V and 12V heat cartridges are seated properly in their steel tubes.Each
cartrige has a screw on the bottom of its steel tube, that holds the
element in proper position.You can see these screws  just above the burner
box. The largest percentage of heat transfer from the element is by
conduction.However, the heat that is radiated is also necessary,in addition
to the conducted heat,or the refrigeration wont happen. This means that the
element must be pressed right up tight against the main ammonia holding
tube ,just above the burner,with the set screw. This does not mean that the
top of the heat element is also pressed tight against the ammonia tube. I
wedged a piece of metal in the top,to help push the element up tight.It
only takes a minute air gap to destroy metal to metal conduction. Air to
metal is 1/25 as efficient in heat transfer, as metal to metal , or water
to metal(the automatic transmision cooler inside your radiater is liquid to
metal, so it  dosent need to be large to cool ok).The oil cooler on late
vanagons or vanagon  automatic transmission coolers are exampels of this
liquid to metal conduction principal.Small ,arnt they? Dont underestimate
what they do.

If the refrigerator is working ok on propane,it should work ok on 110V,and
vice versa.The galvanized insulation shield that is around the lower heater
pipe,is ez to remove.Just sqeeze it and it will unsnap.Dont damage the
fiberglass insulation,cause replacement insulation will smell bad.Real
bad.The refrigeration effect will not work without this
insulation,either.By removing ,or just loosening up on the shield, you can
inspect the tops of the electrical  heat elements.Total removal of the
insulation should be done by removeing the stainless steel screws inside
the burner box, and spreading the tubes apart.That insulation tears easy.

Poor refrigeration can also be caused by an improperly installed evaperator
plate(ice cube tray holder).This plate also uses the conduction principal
of heat removal for the majority of heat transfer(90%). Most of the heat
enters a space of 1/2 inch by about 9 inches ,where the plate clips onto
the black steel refrigerant pipe , at the rear of the frig.The end of this
black pipe has a cap on its upper end that is a bit larger in diameter than
the rest of the pipe.If the evaperation plate is clipped over this cap,it
will cause an air gap between the plate and pipe for the entire length of
the plate. Little conduction will occur.Air to air heat transfer will
occur,and this is 1/25 as efficient as conduction. Old dry ,and crusty
mastic, that is between the plate and pipe(for good contact),can cause a
percentage of this 4.5 sq. inches of conduction area to be reduced.

The black pipe is about 9.5 inches long , and the plate is about 9 inches
long where they make contact. To get the very best heat transfer, place the
plate as near the end cap,to the left, as  possiable ,without actually
placing the plate over the cap. You have about 1/2 inch of space to play
with. This makes a difference, as the coolest part,by far, of the black
pipe,is to the left(by the ice cube trays). The idea is to mount the plate
to the coolest 9 inches of black pipe , possiable.


A clean orifice is most importiant.Injecting rubbing alcohol through it
wont work on a 20 year old orifice. The issue is oxidation. This hole is so
small , that it can oxidize closed. I used a week solution of battery acid.
I pushed on a rubber hose ,to one side of the orifice and added a bit of
acid, with an eyedropper. I let it drip its way though. Nice and clean now.
Got rid of the oxidation. I rinsed with alcohol,lots or it. I tested the
results with a manometer. I did a before and after test. Then I got a brand
new orifice and tested it for the amount of time it took to reach 11 inches
of water column. The old oxidized orifice took about 3 more seconds to
reach 11 inches , than the cleaned or new orifice. The cleaned orifice
matched the new orifice.This old orifice was first cleaned with rubbing
alcohol without any improvement at all. From this, I can say that maybe the
cleaned orifice will reoxidize faster since the acid etched the hole and
made  a much larger, potential surface area(microscopic ?), for new
oxidation? I know alcohol is a waste of time, so maybe a new orifice is the
only long term solution to a restricted orifice.

Dont forget to check the ignitor where it bends 90 degrees and enters the
burner box. the cable can crack and a spark will jump from this crack to
the box,instead of from the electrode to the burner.Like a bad spark plug
wire on an engine. You can hear the  spark leak out of the wire and ground
to the engine block.Snap---it sounds. At night ,you can see this occur.

Lastly, I cleaned the vent out with a test tube brush and something that
will remove the rust.Maybe marine clean,or that other por-15 product.I did
this to get the waste heat out as efficently as possiable. That rust causes
drag of the exhaust. The first 5 inches of the lower vent is where the
greatest proportion of heat transfetr takes place. After that ,the heat is
a liability(hot interior of van).Maybe that por 15 paint for exhaust
manifolds will keep the rust from returning.