Date:         Tue, 27 Jun 2006 11:08:02 -0400
Reply-To:     Roger Sisler <rogersisler2000@YAHOO.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Roger Sisler <rogersisler2000@YAHOO.COM>
Subject:      Re: Dometic question. (yes did search archives.... ;^)

A couple of months ago , someone posted that the inside dometic tempature
rose a few degrees just before the frig kicked in for cooling. I think this
is the added heat from the burner on high. Because of this ,I suggest a
aluminum flashing material between the cooling fins and the rear of the
dometic. Like a heat shield on a muffler.Just a small break in air space is
all that is needed(thats all your gonna get).

Also a sheet of fiberglass insulation on top of the frig.

Sounds like removel and a regooping of the aluminum evaperator may help
you. It just wiggles off. Be careful of the thermistat probe that is behind
the plate.

Radio shack has a thermal heat sink compound in a tube that will work(1
tube).When the plate is reattached, be careful that the plate is not
pressed on directly over the left end of the balck  pipe. This end cap is
of a larger diameter than the rest to the pipe, and it will cause the plate
to not seat properly.However, this end (where ice is made) is  also the
coldest part of the black pipe. Place the plate as close to the end cap as
possiable.About 1/4 inch away from the end.Capture as much"cold' as
possiable.

The heat inside the frig is conducted into the aluminum fins and back to
the black pipe. The actual place where the metal to metal contact of the
balck pipe and aluminum plate is made , is about  1/2 inch wide, and 9
inches long.It is the aluminum extrusion flang.  90 percent of the heat
removed from the inside of the frig , goes through this small area.The
remaining heat is conducted through any extra surface area on the black
pipe that is not covered by the plate flang.This is why proper contact of
the two pieces is critical.The origional green mastic can dry and crack.
Any air gaps that result, reduce this contact area.Air gaps,no mater how
small,result in air to metal heat transfer.It  is 1/25 as efficent as metal
to metal or water to metal, heat transfer.When your talking about 4.5
sq.inches of surface area, any bubbles are too  many bubbles.

 Look at the automatic transmission cooler in the radiator of an american
car .It is puney. This is because of the efficent heat transfer of water to
metal,and fluid to fluid. The radiater that this cooler is mounted in uses
air to metal, and needs to be as large as it is. Another water to metal
device is the oil cooler on the vanagon diesel or 2.1. Dont underestimate
it.

The contact area of the two components , in the frig, may(dont know for
sure) actually be increased by adding a fillet of a thermal compound of
some kind on each side of the 1/2 inch area.Perhaps a heat sink mastic of
some kind. I wasnt successful in finding a good material last winter.What I
tried, drooped and smeared. Perhaps a layer of some material can be added
on the bottom edge,with the frig installed by using your finger to apply
it.


Also, the door sealing needs to be checked ,some way.

When you burp it, tap the pipes with a  rubber hammer every few hours or so.

Type in "manometer" in yahoo, and find instructions for making and using a
manometer($2). Check our regulater pressure.

The brass orifice will almost oxidise closed in 25 years.Rubbing alcohol
will not not not remove this oxidation, and you are wasitng your time with
it. I borrowed a tiny bit of battery acid and diluted it 4 to one. I
attached a rubber hose to the orifice and let it drip through. With the
manometer, I compared it with a new brass orifice. It matched in the
ammount of time it took a collum of water to rise 11 inches.Previously,
with a alcohol bath, I got no change.The collum of water took much longer
to rise to 11 inches.Now,you can rinse it in alcohol when the acid has done
its thing. A ruby orifice in late vanagons is different, and may not clog
as easily. Rubbing alcohol mahy help it. Ruby orifice,$80.


Dont toss your dometic or trash it verbally till you do these maintianance
proceedures.Toss it my way if you need to vent. It will work better. It is
rare that a ammonia circut actually gets clogged. Many blame the bad
dometic  preformance on this.