haze5736
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1970 Fan Lee Liner 16'
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Post by haze5736 on Jun 23, 2024 7:29:40 GMT -8
I recently picked up a used Norcold Model 643 two-way fridge, propane and ac. I have no idea what the relative age of this unit is.
After getting it home I plugged it in to test ac operation. It seemed to cool fine. The freezer area got nice and cold.
I'm finally getting around to testing the propane operation. At first I didn't do any work to it and just lit it to see what happens. It lit up fine. Nice and easy. But I noticed it was not cooling and the cooling fins on the back were not getting warm. The flame seemed a little weak. So I did some basic cleaning. I took the vane out of the chimney and it was covered in a thick layer of soot. I got that nice and clean. I cleaned up the thermocouple and blew away the dust, soot and debris from the burner. I cleaned all the dirt and debris from the entire exterior. I put it back together and installed it in the camper to test.
When I turn the gas valve/lever on I can hear a click. I lit the burner and it stayed running very quickly. The flame looks good and strong. Nice blue color. No flickering. I turned the thermostat all the way cold. I do not hear a click when operating the thermostat knob from full warm to full cold and back. I'm not sure if that is normal. The electric side thermostat does click when operating the knob in this way. I do notice now that the cooling fins get pretty warm. I think that indicates it is working. But the fridge does not get cold. The metal in the freezer did seem like it was trying to cool and some condensation was forming. But it is not getting cold. I did this test on a hot and humid day.
Is anyone able to help me troubleshoot this?
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Post by vikx on Jun 23, 2024 10:39:03 GMT -8
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.
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haze5736
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Post by haze5736 on Jun 26, 2024 3:57:11 GMT -8
I performed a more precise experiment on the fridge yesterday. I ran it on shore power overnight with a thermometer in the fridge on the middle shelf. The temperature reading was 32F the next morning.
The cooling unit is fine and the electric heating element is working as well. The gas and electric heating elements heat up the same components. This narrows the problem down to the gas side of things. From what I've read this usually indicates that the gas flame is not strong enough. I did notice that as I adjust the gas side thermostat the size of the flame changes. So I'm guessing the thermostat works. It would seem this is not actually a thermostat and just a flame size adjustment? Possibly the reason I don't hear a click when I turn the knob. Does anyone know if this is true? Or should it also click on and off?
The last cleaning I did was just on the chimney and a blow out of the burner surface. I did not take the burner out to inspect and clean. I also did not clean or inspect the gas jet. I guess that needs to be my next step. It seems this fridge is rather simple. There are only so many things on the gas side that could cause a weak flame. It has to be either a dirt/debris problem or the gas supply is inadequate. I suppose it could be a combination of both. I did notice that the copper supply tubing has an S bend in it and it is rather sharp at one end and possibly slightly flattened. But not by much, it is barely noticeable. I don't know how sensitive these things are and if that bend is enough to cause a restriction. I'll start with the easy things first and bend a new supply line if I still have a problem.
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John Palmer
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Post by John Palmer on Jun 26, 2024 7:47:29 GMT -8
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
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Post by vikx on Jun 26, 2024 12:29:09 GMT -8
Leave the gas on overnight as you did the electric.
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Post by Teachndad on Jun 27, 2024 6:27:56 GMT -8
I turned the thermostat all the way cold. I do not hear a click when operating the thermostat knob from full warm to full cold and back. I'm not sure if that is normal. The electric side thermostat does click when operating the knob in this way. I did this test on a hot and humid day.
Is anyone able to help me troubleshoot this?
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
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haze5736
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Post by haze5736 on Jul 1, 2024 16:42:25 GMT -8
I did run a test on propane overnight. Temps were in the 50s. The metal cooling surfaces in the freezer only got slightly cool. Not cold at all. I did notice that the thermostat goes from a low flame on the defrost setting then to a high flame as soon as passing the defrost setting. The flame is strong and a good color. I initially checked it after a couple of hours and I got excited because it seemed like it was cooling. But overnight it seemed to stop cooling. There was lots of heat coming off the fins in the back. I'm really starting to suspect a bad thermostat. It seems like the thermostat is not working. It seems like it eventually overheats and stops cooling. Does anyone know how to test a thermostat? And more important, is it generally possible to find a suitable replacement when an original is not available? I know on my furnace I was able to find a suitable replacement gas valve even though the original was no longer available.
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John Palmer
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Post by John Palmer on Jul 1, 2024 20:24:41 GMT -8
I did run a test on propane overnight. Temps were in the 50s. The metal cooling surfaces in the freezer only got slightly cool. Not cold at all. I did notice that the thermostat goes from a low flame on the defrost setting then to a high flame as soon as passing the defrost setting. The flame is strong and a good color. I initially checked it after a couple of hours and I got excited because it seemed like it was cooling. But overnight it seemed to stop cooling. There was lots of heat coming off the fins in the back. I'm really starting to suspect a bad thermostat. It seems like the thermostat is not working. It seems like it eventually overheats and stops cooling. Does anyone know how to test a thermostat? And more important, is it generally possible to find a suitable replacement when an original is not available? I know on my furnace I was able to find a suitable replacement gas valve even though the original was no longer available. 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
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newin62
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Post by newin62 on Jul 2, 2024 2:08:24 GMT -8
One more thought.
Because you say there is a lot of heat coming off the fins and it was cooling at first, it sounds to me like you have a ventilation problem.
Try running the fridge with the rear ventilation covers removed or force air up through the back with a small fan. Also there should be very little clearance between the wall behind the fridge and the upper cooling fins so that all the rising air flows through the fins and not around them.
Many new absorption fridges have 12 volt fans installed that force air over the fins. Also the installation instructions are very particular about keeping minimal clearance between the rear of the enclosure and the cooling fins.
Peter
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John Palmer
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Post by John Palmer on Jul 2, 2024 6:27:40 GMT -8
One more thought. Because you say there is a lot of heat coming off the fins and it was cooling at first, it sounds to me like you have a ventilation problem. Try running the fridge with the rear ventilation covers removed or force air up through the back with a small fan. Also there should be very little clearance between the wall behind the fridge and the upper cooling fins so that all the rising air flows through the fins and not around them. Many new absorption fridges have 12 volt fans installed that force air over the fins. Also the installation instructions are very particular about keeping minimal clearance between the rear of the enclosure and the cooling fins. Peter 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
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haze5736
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Post by haze5736 on Jul 3, 2024 6:19:24 GMT -8
I appreciate the additional replies and support in trying to figure this out. One thing to keep in mind though, is that the fridge works perfect on shore power. This means the cooling unit is working properly. There are no visible refrigerant leaks. I also think it is safe to assume there is not a ventilation problem. The electric and propane heating elements heat the same thing and vent the same way. The vents to the outside are sized correctly and in the proper places. I also have aluminum flashing installed above and on the sides to make sure the air currents are moving the way they are supposed to. Since the fridge works on electric I'm certain this is an issue with the propane side of things. So, if the cooling unit is good, the flame is good, ventilation and air flow are good, what else can it be?
From what I can tell it can only be:
1) Propane delivery problem - I suppose my perception of a good flame could be wrong. I don't have a manometer to test fuel delivery with 100% accuracy. I have cleaned and re-cleaned the propane components.
2) Thermostat problem - can the thermostat be broken or stuck in a too warm position? Is the propane thermostat supposed to click at some point when it is moved through the workable range? Mine does not. The electric side does. The gas thermostat on my gas furnace does.
Is there another potential problem that I'm missing?
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John Palmer
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Post by John Palmer on Jul 3, 2024 8:50:03 GMT -8
1) I think if you have a nice blue flame, and it does not need to be a large flame, I think your LP flow is good. If the LP regulator was not working, you would not have a good flame, not much to check knowing the actual pressure in inches of water.
2) If you have a mechanical thermostat, I think you might hear a clicking sound when it cycles on/off while turning the knob. But if it's a Mercury Bulb type, I would doubt that you would hear anything.
3) I like your thought process of elimination. Thanks for reminding us that it works on electrical.
I think at this point, I would disconnect the thermostat, and use a voltage/continuity meter to test if you have any changes when you move the thermostat through its range. What exactly does the thermostat control? Does it start/stop the heating element? Does it go to a regulator to turn the flame on/off, up/down? Can you sue a jumper wire to bypass the thermostat, and does it then work? Basically, you need to eliminate all of the possibilities before you go on a wild goose chase trying to find a replacement thermostat.
The thermostat has a thermocouple bulb that senses the temperature, it's like the sender to your car's temperature gauge. It has to be clipped to something to sense the unit's temperature, maybe check the condition of the thermocouple tube and bulb end.
LOL, I think we are both running low on more things to check.
John Palmer
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