Norcold Refrigerator Model 643 Troubleshooting

Old RV fridges are often bad. (I believe yours is 1964) Repair parts are unavailable. We used to be able to replace the "coils" or cooling unit, but I haven't seen any available recently.

It sounds to me that your cooling unit may be failing. The freezer gets cold, but the fridge portion is not cold enough. Did you measure the temperature in the fridge bottom half? It should read 40* or less.

If it works on electric, you may have to use shore power for now. I don't think your fridge is going to last. Sorry.

You're on the right track.  Take apart the LP side and clean anything you can disassemble without damage.  For example, be careful moving any "very small" aluminum or copper lines.  Do not open the coolant side, or the Thermocouple to the thermostat.  The pressure of LP going into the unit is very low, less than 1 psi.  It takes almost nothing to plug up an LP line.  For some reason the oily LP surface and the LP smell attracts very small spiders, and they build their webs in the lines and gas jets.  Sometimes it takes more than a shot of air to clean the jets out.  If you manually clean the jet (s) just make sure you do not enlarge the jet hole size.  My guess, is that the flame size adjustment you found is so that the flame can be adjusted to burn cleanly at different altitudes.  Good hunting.

John Palmer

Hi,

I can't answer the bolded part of your initial post.  Maybe someone else can.

Is the camper level?

I am glad running the fridge with electricity showed positive results. Your logic to start simple in diagnosing makes sense. I think with any deductions in problem solving, the test variables need to be the same. I think that's what Vikx is getting at. Initial test was during a hot and humid day when the gas was running, then second test was during the night with electricity and (I assume) outside temps were cooler. Third test should be with gas running at night and then compare with earlier gas test. Test 4 would be with electricity running during the day. This assumes temperature and humidity are consistent.

Not sure of your location. I have been in places during the summer when it's 100 degrees outside and then cools to a nice comfy (sarcasm implied) 94 degrees - Lake Havasu, Az. So, night time temps don't always change widely, LOL.  

I was trying to get a fridge in a 1985 Starcraft pop up working a while back. First test was on a very hot day at @90 degrees and it barely cooled. Then ran it later when temps were cooler and the fridge cooled significantly better.

Cheers,

Rod

Two different thoughts.

I believe your refrigerator is what is called a heat exchanger (no compressor, or freon).  It uses the ambient temperature, and when the flame heats up the ammonia it expands as it passes an expansion valve and the quick drop in pressure results in the cooling effect.  On "a perfect unit", it might cool something like 40 to 50 degrees below the ambient temperature.  So in 70-degree weather it will keep your popsicles frozen.  But, in 90-degree weather you're going to have a hard time keeping your Cereal Milk fresh.  As they get old, the ammonia cakes up and does not cool as well as when it was newer.  If you see anything that looks like yellow powder, or any kind of smell, it has a leak and is dead.  If the flame is a nice blue, not yellow, and the coils are hot (as they should be) I would not think the thermostat is the issue.  If it was freezing your milk, then the thermostat might be the cause.  But in your case,   it is not cooling.

Thought #2, I work on 1940's GM Frigidaire Refrigerators for my early Spartans.  I use a company called Antique Appliances located in Georgia for my reproduction door seals.  I believe I have seen them advertise generic refrigerator thermostats that can be adapted to various makes of refrigerators.  My only question would be if these are only for electric compressor type refrigerators, and not heat exchangers powered by propane flame.  At worse it would be worth a look see.

You're not the first guy that has been challenged by tying to make an old RV refrigerator come back to life.  Several of my friends have purchased small modern refrigerators and adapted the old vintage style door and handle to the new refrigerator.  Going that route gives you a 110v working refrigerator, and the vintage looks.  But it's not a good choice if you're a dry camper without an abundant 110v power source.

John Palmer

 Peter, a great "one more thought".  Thank You for adding the reminder.

All refrigeration works by absorbing the heat inside and transferring it to the outside.  Your car, your house, your vintage refrigerator are all the same principal.  It makes no difference if it's an Absorbtion type or a freon compressor type.  It's the outside air flow that dissipates the collected "inside" heat.  Having good ventilation is paramount to the operation.  Since heat rises, you want to have a clear intake "air flow" path at the bottom, and a clear "air flow" exit path at the top for the heated air to escape.  If the heated air can escape to the outside of the trailer all the better. 

The reason the original instructions stated the LP type refrigerators had to be "leveled" is so the heating flame would be aimed straight up the heating coil flue for maximum coolant heating effect and efficiency.  This is just as important as the proper ventilation, and I'm not sure we have bantered that point around yet.

I like your term Absorption Refrigerators, that is exactly what they are, and a better description than my term Heat Exchangers.

John Palmer