Date:         Mon, 21 Nov 1994 10:33:11 -0500
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         DerekDrew@aol.com
Subject:      Refrig. Operation Manual Part1

Refrigerator Madness
copyright 1992 by Derek Drew

This file may be reporduced and redistributed for any non-commercial purpose.


Here, in no particular order, is what you need to know about your VW Vanagon 
Refrigerator so you can use it properly and get the most out of it.
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Basic Theory And Operation

Efficiency Of The Three Modes

I have tested several Vanagon Camper RM 182 B refrigerators under controlled 
conditions in all three of its modes: propane gas, 110 volt electric, and 12
volt electric. 
Under controlled conditions, all three modes produce nearly the same degree
of cooling. 
This came as a suprise to me, since long experience suggested that best
results were 
achieved with 110 volts, next in line was LP Gas, and worst of all was 12
volts. In a 
moment I'll try to explain the puzzling results.

But first, it is important to understand a queer thing about how the
refrigerator works. 
Basically, the refrigerator produces cold inside when you apply heat at the
back. The 
heat can either be a flame (which you get from LP Gas operation) or from one
of two 
electric heater elements (one which works on 110 volts and one which works on
12 
Volts). 

Once heat is applied to the back of the refrigerator the most important thing
to 
remember is that nothing happens for 20 minutes. Then, after the 20 minutes,
the 
cooling power rushes in to the little fins inside the refrigerator and cold
is produced. 
Within a very short time the fins are as cold as they are going to be.

12 Volt Operation

The forgoing will help to explain some of the reason why it appears that 12
volt electric 
power doesn't work very well. You must understand that the 12 volt electric
power is set 
up by Volkswagen to work only when the alternator is producing 12 volt
current, 
something that only happens when engine is running. Because nobody lets their
engine 
run for very long without shutting it off--for example to get gas, food, or a
snack--the 
refrigerator on the 12 volt setting is always being shut off and then turned
back on. This 
upsets the cooling cycles and unless you are on a very long trip with steady
driving, no 
significant cooling will be achieved.

If you are trying to make the 12 volt power work anyway, there is a trick
that you can do 
to allow the 12 volt operation to work even when the engine is off. You would
enable this 
mode, for example, when you were planning to make short stops on a long trip
and you 
wanted to keep the refrigerator on all the time. Of course, you have to watch
out and not 
allow the refrigerator to run too long in this mode, however, since the
refrigerator draws 
eight amps, enough to kill your battery in a few hours. 

The simplest way to allow 12 volt operation of the refrigerator with the
engine off starts 
by finding the little black fuse box behind the driver on the wall just
behind the door. 
Take the cover off this little black box and observe that there are two
fuses. These fuses 
protect two wires going back to the refrigerator area, one of which has power
when the 
engine is running and one of which does not. You can enable to refrigerator
to run off 12 
volts with the engine off by connecting, temporarily, these two wires. 

A possible setup would accomplish this with a switch connecting the two wires
further 
down the line toward the rear of the vehicle. A simpler (jury rig) setup
would be to take 
a very light duty clamp that is electrically conductive and shaping it so
that it contacts 
the little metal pieces that hold these two fuses. I don't get recommend this
latter 
practice, however, since it is dangerous, but I point it out so you can get
the idea of 
connecting these two wires together. (Note that this clamp, in the position I
mention, 
would be electrically live and if it touched any bare piece of metal, the
result to your 
camper could be catastrophic.)

The ultimate setup to allow 12 volt operation with the engine off would
involve the 
installation of a second battery under the driver dedicated specifically to
this purpose. 
Dennis Haynes wrote an excellent technical article on his theories of how to
install a 
second battery for this purpose in an early issue of the LiMBO newsletter.
This is the 
newsletter published by the Late Model Bus Organization headquartered in the 
northeast.

I will limit my own comments here to the following points: consider using a
deep cycle 
marine style battery instead of an automotive battery since marine batteries
are not 
destroyed by being discharged. Automotive batteries do not like to be run
down and 
recharged. Do not simply connect both batteries in parallel or the weaker one
will 
constantly drain the stronger one and there will be other undesirable
effects. Do not 
allow the refrigerator to draw power from more than one battery while the
vehicle is off 
or you may not be able to start your vehicle when you need to. Do not use a
"dual battery 
isolator" to keep your two batteries separate because the VW 90 amp
alternator supplied 
with the Vanagon doesn't push enough volts to overcome with grace the voltage
drop 
that a standard dual battery isolator imposes. Instead, use very high power
relays. 

Consult me by phone or an expert if any of this material is unfamiliar to you
as it is 
hard to get good information about how to do it right. Alternatively, call
Dennis Haynes 
by phone. His approach is a little different than mine, but it has
advantages. Never 
operate your vehicle with neither battery connected or you have a good chance
of frying 
your computer brain that controls electronic ignition.

The Importance Of Temperature Measurement

No subject will bring about as much concern to the Vanagon Refrigerator owner
than 
temperature. Is the refrigerator working right? Is it cold enough? Is my food
going to 
stay cold?

Firstly, you will drive yourself crazy wondering whether the refrigerator is
really cool 
inside unless you have a way to measure the temperature in there. There are
two things 
to measure. First, by measuring the air temperature inside the refrigerator
you will 
know exactly the temperature that is reaching your food. Secondly, measuring
the 
temperature of the actual little metal cooling fins inside the unit will
basically tell you 
whether the refrigerator is on or not.

Here is an example, and it shows why it is so useful to keep tabs on both of
the two 
temperature measurements:

Let's say you see that the air temperature inside the unit is 55 degrees
(warm 
enough to spoil your food). Then let's say that the temperature of the
cooling fins 
inside the unit is 25 degrees. This state of affairs might occur if, for
example, you 
had just left the door open for awhile or you only recently started the unit.
Since 
the cooling fins is an adequate 25 degrees, you would know to just sit tight
and 
the air temperature would eventually drop. All is OK. 

But let's say the situation is reversed. You see that the air temperature is
25 
degrees and the temperature of the cooling fins is 55 degrees. This means
your 
cooling fins are not cooling! This might happen if the food was frozen (thus 
cooling the air), but the cooling fins are not cooling. Possible causes for
the 
cooling fins not cooling might be: 1) you just turned the unit on, and so you

shouldn't expect 25 degree temperatures for a half hour or so, 2) the
refrigerator 
thermostat is set too low, 3) the unit just turned itself off for some
reason, such 
as that the flame blew out. In case 3), you would have an early warning that
the 
unit had been turned off long before the food spoils.

The best way to measure the temperature is by using little thermometers with
probes 
that are attached on the ends of wires attached to the thermometer. Radio
Shack carries 
a nice little unit that is reasonably priced for this purpose. I mounted one
of these 
probes so it was just hanging in the air (not touching anything that might
make the 
reading false) and I mounted the other one with GE clear silicone glue right
on the 
cooling fins. I chose to glue this probe in the back of the fins so it was
not visible from 
someone looking in to the frige. I also applied silicone-based "heat sink
compound" 
between the probe and the cooling fin to ensure maximum thermal transfer of
the cold 
from the fin to the probe.

I mounted both of these thermometers next and to the left of the driver's
head on the 
wall with contact cement so that the driver could quickly see if something
was wrong 
with the refrigerator and what its condition was. I routed the probe wires
through the 
back of the refrigerator so there were no messy wires running out the
refrigerator door 
but this is by no means necessary.

The Sad Truth About Temperatures

The two thermometers taught me a lot about the efficiency of the
refrigerator. It taught 
me that there was no problem in getting the temperature of the cooling fins
down to 
around 17 degrees or so, an excellent temperature. But on a hot day, the air 
temperature inside the refrigerator, especially with lots of food packed in,
was barely 
adequate--high enough so milk would quickly spoil. Basically, I discovered
that the 
Dometic 182 B refrigerator doesn't really work as intended despite adequate 
temperature of the cooling fins.

The Golden Path To Refrigerator Happiness

The obvious answer was that air currents were needed inside the unit to cause
air to 
flow off the cooling fins down and over the food. I located a suitable 12
volt fan at Radio 
Shack that draws so little power you can leave it on all day and I installed
it over the 
cooling fins, firing air down passed them and onto the food. 
Ever since then my air temperature and food temperatures have been below 40
degrees 
even in the hottest weather. Hooray!

The easiest way to obtain a good little air circulation fan is to obtain a
battery operated 
refrigerator fan such as are sold at RV and Motor home stores. If the store
doesn't have 
the fan in stock, check their catalogs as they can certainly order one. The
Camping 
World catalog (Bowling Green, Kentucky and elsewhere) also has this fan (I
think), as 
do some marinas.

If you can't find a fan made for RVs, find anything that will create air
turbulence inside 
the refrigerator. 

The importance of adding an air turbulence fan to the inside of your
refrigerator is 
probably one of the most important tips inside this entire article for you to

follow. 

The ultimate setup has the fan mounted directly over the fins. If you decide
to use the 
vehicle's 12 volt current and buy a Radio Shack fan like I did, be sure and
buy the very 
small 12 volt fan instead of buying the larger 12 volt fans that Radio Shack
stocks. The 
fan I am talking about is about the size of a matchbook.
I put a switch on my fan so I can turn it on only when I am keeping food
inside the 
refrigerator.

Adding A Rear Fan

The last ultimate setup for creating a colder refrigerator has to do with
methods to 
exhaust heat away from the fins in the outside (rear) of the refrigerator.
You can't see 
these fins when the refrigerator is inside the vehicle but proper operation
of the 
refrigerator requires that these fins be able to dissipate sufficient heat.
The heat that 
comes off these fins travels up behind the stove/sink area and passes by the
left side 
window of the van. 

A thermostat is set on these fins so when the temperature of the fins reaches
around 125 
F degrees or so a little fan comes on to push air passed them. A few things
can go wrong 
here. 

Firstly, the thermostat can loose contact with the metal fins on which it
sits and 
therefore it never heats up to 125 F and therefore, the little fan in the
back never comes 
on. Just to make sure there is a good thermal bond between the refrigerator
fins and 
this thermostat, it is good practice, any time the refrigerator is out of the
vehicle, to 
remove this thermostat, coat the bottom with "heat sink thermal silicone heat
transfer 
compound" (a white paste available at Radio Shack), and reinstall the
thermostat with a 
thin layer of this goo between the thermostat and the fins. While you are at
it, be sure 
the mounting flanges of the thermostat correctly push the thermostat solidly
against the 
black metal fin.

The little fan pushes air upwards passed the fins, but the fan itself is
idiotically small 
and doesn't push much air. I installed an extra fan on the back of my
refrigerator next 
to the stock fan. I bought this fan at Radio Shack and selected a 12 volt
model they sell 
that is about the size of a pack of cigarettes. 

I don't this step is necessary but it significantly adds to the capacity of
my unit to shed 
heat at the back so you might want to do it too. Included with this package
should be a 
photograph showing the location I selected to mount the fan. I soldered the
electrical 
leads to this fan to the stock factory fan so it too would be controlled by
the thermostat.
Long Island's Dennis Haynes said he feels another approach would be to form
an air 
baffle that would sort of surround the fins at the back of the refrigerator.
This shield 
would force the air coming from the fans to go passed the metal fins and
provide extra 
cooling, Haynes feels. Otherwise, a lot of the air from the cooling fans just
blows around 
behind the refrigerator without doing its intended work. I haven't yet
decided whether 
this approach is for me yet.

Problems

If you're not up to performing any of the repair procedures listed below
yourself, you 
might also consider asking your favorite mechanic to do them for you. You
could 
photocopy this material to give to him.

LP Gas Flame Goes Out While Driving

The Vanagon refrigerator, when operated on LP Gas, develops a little flame
you are 
supposed to be able to see in the sight glass in the far inside left rear of
the refrigerator. 
This flame sometimes blows out while you are driving around but it is not
supposed to. 
There isn't anything unsafe about it blowing out but it turns the
refrigerator into a 
major pain because you won't notice it when the flame first blows out. Your
food has 
enough trouble staying cold when the unit is always on. Vanagon owners should
take all 
measures to fix their refrigerator if it is blowing out on the road.

The procedures to follow to fix the LP Gas flame blowing out require you to
remove the 
refrigerator from the vehicle first. Some help can be found on how to do this
by common 
sense and reading the Bentley manual mentioned above. There is also an
excellent 
Volkswagen factory video tape made for its mechanics to train them in exactly
how to do 
it. You can order this tape from me or perhaps borrow it from your local VW
dealer.

POSSIBLE CAUSE #1: Once out of the vehicle you will see that the refrigerator
has two 
round vent pipes that go from the refrigerator up to the side of the vehicle.
These pipes 
are there to bring fresh air down to where the flame is so it has oxygen and
to vent the 
hot air created by the burning to the outside of the vehicle. Dometic's
standard line as to 
why the flame might blow out while driving is that these pipes are not of
exactly the 
same length. Dometic claims that they must be the same length down to the
smallest 
measurement or it will cause unequal air pressure between the two pipes while
driving. 
Unequal air pressure, Dometic says, will result in air blowing through the
combustion 
chamber (the little box where the pipes join, and where the flame is) which
creates a 
draft in that chamber, thus blowing out the flame.

Soooo, the repair here is to cut the longer of these two pipes by a small
amount so they 
are exactly equal in length. You could probably do it with a hacksaw. 

POSSIBLE CAUSE #2: If you look the back of the refrigerator you will see the
small 
metal box at the right rear at the bottom--the combustion chamber. The lid of
this box is 
screwed on to the bottom portion with screws. In between these two halves of
the box is 
a rubber gasket (usually red) which seals air from getting in or out of the
box. 
Sometimes, this gasket can develop small leaks which allows a draft to
develop into and 
out of the box, thus blowing out the flame. Alternatively, a previous
mechanic might 
have serviced this box and decided to reassemble it without the gasket, not 
understanding its importance. The repair task here is to replace the gasket
or otherwise 
seal the edges around this little box with silicone glue or other material to
prevent any 
air leaks. Air leaks here cause the same draft effect in Possible Cause #1.

POSSIBLE CAUSE #3: Blockage in the supply of gas. Sometimes grit can get in
the tiny 
orifice that lets gas into this combustion chamber. Use alcohol and clean out
this tiny 
metal orifice.

POSSIBLE CAUSE #4: Foreign object in the vent pipes. Sometimes material can
blow 
(or crawl) into the two vent pipes and lodge in there. Cleaning this out will
restore 
proper operation. 

POSSIBLE CAUSE #5: The little metal screw that blocks off the drainage pipe
(and 
keeps air from entering or leaving it) has come off. Replace this screw. If
the screw is 
missing you will have an air leak or draft similar to the one described in
Possible Cause 
#1. This is the only repair you can do with the refrigerator still in the
vehicle. To find 
the drain pipe kneel in front of the refrigerator. At the bottom left, next
to the floor, you 
will see the small metal drainage pipe.

Unit Is Hard To Light

This can be caused by many factors but here are a few things you can try
without 
removing the unit:

1. Try wildly pumping the air supply pump at least 30 times before pressing
the 
button that supplies LP gas to the refrigerator. This will ensure there is
oxygen 
there for ignition when the refrigerator needs it. If you press the LP gas
supply 
button too soon the LP Gas can push away Oxygen that you need for ignition to

occur.

2. Try alternatively pushing the air supply pump/ignite plunger (far left) in
all the 
way over and over again as you press the gas supply button. Each time the 
plunger goes all the way in you can hear a noise as it sends a spark into the

combustion chamber. Who knows, one of the sparks might light.

3. Try breathing or pushing air into the little metal drainage tube that
comes 
underneath the refrigerator to its front left bottom. Alternatively, try
sucking air 
out of this metal tube, into your mouth, and then push the air from your
mouth 
without inhaling any of it. (You will usually notice smoke was in there,
which was 
preventing ignition.) This tube is capped by a little screw on metal plug on
the end 
of a tiny chain, which you unscrew. Blowing air into this little tube may
disturb 
debris in the combustion chamber which is impeding proper operation. It will
also 
cause Oxygen to enter the chamber to make combustion work better. When you're

done, screw the little cap back on this little pipe to avoid problems with
water 
draining onto the floor, or the flame blowing out while you drive.
     
I once saw an RV dealer get a stubborn refrigerator started by blowing
compressed 
air into this hole from an air compressor hose ordinarily used for inflating
car 
tires. There was a lot of pressure, but the mechanic at the dealership felt
this 
much pressure was needed to blow cobwebs, etc., apart that may have been in
the 
combustion chamber. 

In practice, I have found that when my refrigerator is reluctant to light, it
is 
usually because of insufficient oxygen in the combustion chamber, and blowing

almost any amount of air up this little pipe will cause the unit to light
properly. 
This is probably the most useful, and least known, tricks to getting the 
refrigerator lit. Remember it! I keep a little rubber tube under my
refrigerator 
where I don't notice it. Then, when I need to blow air up this little
drainage tube, 
or draw the stale smoky air out of it, I connect the rubber tube onto the
metal tube 
that comes from the frige and I blow air into the rubber or suck air out of
it.

4. Another cause of poor lighting is poor operation of the air supply pump on
the 
refrigerator itself. VW's special bulletin on the air supply modification is
a 
procedure you are supposed to be able to perform (or have performed for you)
in 
order for this pump to work better. I rate the "Air Supply Modification" as 
something you would do if you were desperate, or especially if the unit was
still 
under warranty. Its always easier to perform step #3 immediately above,
which, 
conceptually, accomplishes the same thing as the Air Supply Modification.

5. If the unit won't light it could be that the LP gas tank wasn't properly
"purged" 
after having first been put into service. Before an LP gas tank is used for
the first 
time it is supposed to be properly purged to remove impurities but nobody
knows 
to do this with VWs so there could still be contaminants in the tank impeding

proper operation of the refrigerator. Any well equipped large RV rapier
facility 
which deals with propane will have the proper stuff to purge your propane
tank.

General Problems

Cleaning The Combustion Chamber

Note that over time the combustion chamber in the RM 182B accumulates debris
and 
soot that must be periodically cleaned out. Instructions for how to do this
are in the 
manual. The refrigerator must be removed from the vehicle for the vehicle to
perform 
this service. Sometimes, cleaning the combustion chamber can be avoided by
blowing 
compressed air into the drain pipe as described above.

Permanent Damage

It is always possible that the refrigerator has been damaged beyond repair by
being 
operated in an off level condition. That is, if you park your vehicle on a
hill and then let 
the refrigerator run, it will ruin it--not immediately, but over time. I have
never seen 
this actually happen, but it is a theoretical reality.

The Gas Valve

Some have wondered whether there is anything special to know about the gas
valve 
located at the propane tank. The bottom line on this is that it will not wear
out with use 
so don't worry about that. But it will be harmed if you try to tighten it too
much. 
Tighten it so it is snug and no more.

This ends part 1 of 2 parts of this article.

This file may be reproduced and redistributed for any noncommercial purpose.
All other rights reserved. Derek Drew, 487 Columbus Ave. #3R, New York, NY
10024. 

derekdrew@aol.com