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Refrigerator Madness

Refrigerator Madness
From: Derek Drew
Year(s):  all with Dometic Fridge
Model/Type:  Vanagon Westfalia
Bentley Page(s):  76.24 Fridge R&R
Symptom(s):  Fridge goes out, Fridge not cold


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 think 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 past 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.
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Service

The Unhelpful VW Dealerships
If your refrigerator isn't working right don't expect a VW dealership to be able to fix it. Many VW dealers hate the refrigerator and don't understand a thing about it.

The Unknowledgeable Dometic Repair Facilities
The official place to go for service is an independent service shop for RVs and motor homes which Dometic designates as an official repair facility. This means that they are supposed to have an adequate supply of spare parts and expertise to fix your refrigerator in case it needs repair. Unfortunately, this is usually not the case. The reason is that these repair facilities simply don't see many VW Vanagons and rarely stock parts for the particular model that VW uses, the Dometic model RM 182B. The mechanics are familiar with the many other models of Dometic refrigerator, however, and so they have a fighting chance of being able to fix yours. Also, if spare parts are needed, they can easily order them from Dometic.
It will help these dealers, when you bring in your refrigerator, if you bring along the spare parts list and repair manual included with this package and leave it there until the repair is complete. (You may also want to photocopy for the mechanics 1) the instructions for how to remove and install the refrigerator from the giant $80 Vanagon official VW repair manual published by Bentley and 2) Volkswagen's RM 182B Air Supply Modification bulletin.) The facility is unlikely to have the repair manual and almost certainly won't have the list of spare parts--both of which will often be needed to properly repair your unit. The mechanic, if you can try to see him, will usually tell you sheepishly that he hasn't repaired too many VW refrigerators before (which often means he's never seen one). He will usually appreciate all the information you can give him.

There is an official Dometic instruction program that the mechanics working for its repair facilities can take to learn how to better repair its line of RV refrigerators. Unfortunately, this program gives the mechanics scant, if any, information on repairing the VW Vanagon refrigerator. One reason for the Vanagon refrigerator's orphan status within Dometic may be due to the fact it is manufactured in Luxembourg, of all places, and is considered an oddball item not made in the USA.

Another reason the mechanics aren't that familiar with the unit is that not that many come in for service. This is partly because there weren't all that many VW campers sold in the US. It is also because many camper owners don't understand their refrigerators very well. When the refrigerator fails to function right, they arn't sure why and give up on the unit rather than try to get it fixed. It is also because RV type refrigerators such as the Vanagon's lack a compressor to go bad so they don't break down all that often.

The Hard-To-Reach Dometic Repair Facilities
Aside from the fact that the mechanics have scant expertise in repairing the Vanagon refrigerator there is another bedeviling fact. Basically, aside from the expense, repairing your refrigerator at a Dometic facility involves hours and hours of inconvenience. This is because there are far fewer official Dometic repair shops than there are official VW dealerships and the nearest one is often hours away from where you live. Since the shop probably doesn't stock the parts you may need, you'll usually have to leave your vehicle, drive hours back to your place, and then complete another round trip to see if their repair turned out OK. (Often it isn't.).
To find an official Dometic repair facility locate a shop listed in Dometic's list of official RV repair shops. Make sure to use a current list since these seen to change from year to year--not a good sign but a fact. To get a current list call Dometic on the phone and ask that they send you one.

Given the hassles involved, you can also try your luck looking for RV and motor home repair shops in the yellow pages. Many of these will express a willingness to work on a Dometic refrigerator even though they are not designated as an official repair facility by Dometic. The quality of their work is in even more doubt than an official facility, however, so its up to you.

E-Z Self Service
Many of the things that can be done with your refrigerator are fairly simple to do. Looking at the huge time investment involved to drive all the way to an official repair facility, I decided it would actually save me time to do some of the work myself. For example, I found I could remove and install the refrigerator myself; after I had done it once, I could perform both removal and installation in a total time of about an hour and a half. This way, I could drop the refrigerator off for repair at the facility without having to leave my Camper there. This meant I was not deprived of the use of my Vanagon and also that I didn't need two cars to get to the repair shop.
Doing repairs yourself also makes sense because, typically, a mechanic doesn't have an edge in experience over you in repairing the unit since he sees so few of them.

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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


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