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Refrigeration Troubleshooting


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I think posting a video on how to leak check cooling units is going to make every average Joe think that they can do the job when in reality you can't unless you have the correct tools and experience.

When you work on a machine that is not cooling properly do you use something like what is in the video to find leaks or do you have an alternative method?

How do you determine whether the machine is low on refrigerant or not?

If you determine a machine is low on refrigerant do you just fill it up or do you actually look for leaks?

Assuming you can find a leak do you do any repairs onsite or do you just replace the refrigeration deck?

I noticed that they sell R134A in my local auto parts store is that the same thing that is used on vending machines or is it different?

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When I first look at a machine that is exhibiting signs of low freon I take into consideration a visual inspection, any odd odors, the history of the machine, whether the system has been tapped before, if it's an original or replacement compressor, etc.  My experience tells me that in the absence of an obvious oil leak or the odor of freon that the machine has probably lost freon over many years and that such a leak will be too small to find.  In reality, most cooling systems have good integrity so I will simply do a recharge if I know the system hasn't been recharged in the past 6 months.  My general rule of thumb is that if a system has lost it's charge (from a prior charge or recharge) in less than 6 months, the leak will be easy to find.  The longer a system runs before it is low on gas and especially if it's longer than 1 year since a charge or recharge, the harder the leak is to find. 

 

The best way to determine low freon, besides the obvious signs of a frozen evaporator or only ice on the top corner or even no cooling at all, is to install a quality gauge on the low-side line and read the pressure with the system running.  Some machines already have a Schrader valve brazed onto the low side or maybe, in a previous recharge, a line tap has been installed.  The brazed Schrader valve means the compressor has been replaced or a leak was repaired with the valve being installed at the time of the repair.  It is known that all factory units are sealed with a crimped and soldered fill tube.  The line tap means that they system has been recharged by attaching a saddle valve onto the factory crimped compressor fill tube.  If I need to check the charge on an untapped system then I install the line tap myself so that I can access the low pressure side (low side) of the system.  Seeing the pressure is too low tells me that the system is out of gas, or in some instances, this is a sign of bad valves in the compressor.  Until I begin to add gas to the compressor I don't know what's really happening.  If I find the low side pressure too high, then in the case of a sealed system that I tapped, the compressor valves are bad.  In the case of a previously tapped system it can mean that it was previously overcharged while being recharged or the valves are bad in the compressor.

 

To properly leak check a system it has to come out of the machine.  This is due to all of the potential solder joints and rubbing points that have to be checked, so I don't do this amount of work unless I deem it necessary.  I will always talk a customer into letting me recharge their system rather than pull it to check for leaks just because they want that done.  The customer is almost always money ahead doing the recharge first, then if the gas leaks out in less than 6 months, we know that there is a leak that can be found.  I can count on one hand the number of systems that leaked down again in less than 1 year after just a recharge.  When that does happen, the system is then pulled and repaired on the bench.  In this way I save my customers tons of money and machine down-time.  In the event that a leak we suspect is there cannot be found with a sniffer or visual inspection, we will then inject UV dye into the system while recharging it so that when it leaks down in the future, we will be able to search for the leak with a black light. 

 

I do no brazing on location due to the potential liability of fire.  This is why any system pulled for a leak check is worked on at the shop.  That is where all the tools and materials are for proper and permanent repair.  If a machine has an integrated cooling system that can't be removed, like the USI FF2000 frozen machine, then the entire machine has to be moved to the shop in order to perform anything more than a simple recharge.  I don't replace a system with another if I suspect a leak unless the customer demands it.  I don't keep one of every style system sitting on the shelf ready to go so instead I pull their systems for repair.  I carry on my truck, only one can of freon and it's a blend that can be used on top of R12 or R134a.  It is called R401a or is referred to by it's trade name of MP39.  This blended gas was originally designed to be used as a drop in onto existing R12 or R134a systems, however it has been found to be a very stable gas on it's own and is used in rebuilds.  When I repair or rebuild systems at the shop, I will use either MP39 for units that originally used R12 or I'll use R134a where that was the original gas or is what the compressor is designed to use.  There are different gases used for some frozen and cold food machines, but MP39 and R134a are all that we use in cold drink machines.

 

The R134a that you see in auto parts stores is, in my opinion, a ripoff and a money grab by the parts houses.  There are way too many ways to damage a cooling system or yourself if you don't know what you're doing, whether we're talking about cars or refrigeration equipment.  I'll admit that when I was young and stupid and needed to recharge my R12 car air conditioner, I would just purchase a can of R12 and dump the whole thing in (there were no included gauges back then).  However, knowing what I know now, that can damage a system just as much as fix it and will usually mask a problem such as a leak that is far more prevalent in cars than in vending machines.  Furthermore, it would be a mistake for any vending operator to think that they can buy a R134a kit at Auto Zone and recharge their vending machine.  They would have no idea of what the pressure should be when the gas is added, let alone how to do this if the system has never been tapped.  They will likely have no idea of whether R134a should even be in their system and they risk contaminating their system.  Not every compressor uses the same lubricating oil and the oil dictates the type of freon that can be used with it.  As you can see, working on a cooling system is not as easy as it seems. 

 

The video you posted shows the method of leak detection using a sniffer.  However, this is more likely to be useful with a refrigerator at your house because your refrigerator isn't moved as often as a vending machine, bounced by customers like a vending machine nor work as hard as an outdoor vending machine.  You also have to realize that in a refrigerator or freezer, you can't remove the entire system like you can with a soda machine, so the sniffer is the only method to use to find a leak in a household appliance and they can only test what they can see or reach.  It's also more likely that an appliance repairman will perform the leak repair on location as most homeowners can't do without their primary food storage device for very long. 

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AZ you are right on 100%

 

I had a guy that bugged me for about a week about his garage vendor not cooling. He went on and on for days before finally having me come out and look at it. 

 

First thing I noticed when looking at cooling deck was it had a new  schraeder valve  installed. So the compressor was rebuilt. Then I saw that this guy had put a 134 adapter on the stem. So he had self diagnosed and added automotive 134-A with oil in system. At that point I told him the unit was bad and needed replaced. 

 

​Something that has not been touched here and is very important. Do not add refrigerant to a system unless you are qualified.  

 

​The information contained on this thread is intended to help diagnose a problem  to help save money it is not intended to by any means for you to recharge a system yourself.

 

Adding refrigerant to a bad system can cause bodily harm or a fire or even death. Adding to much can cause a fire. I have seen a compressor blow a hole out underneath the cap where your start relay and overload is and shoot fire out.

 

​The visual information here is very important and will help the unqualified know when he needs a professional. Breaking a line with hot refrigerant can and will blind you if it gets in your eyes. Refrigerant that is on fire is toxic and can kill you.

 

 

Leave the charging a system to the professional!  ;D  ;D 

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AZ you are right on 100%

 

I had a guy that bugged me for about a week about his garage vendor not cooling. He went on and on for days before finally having me come out and look at it. 

 

First thing I noticed when looking at cooling deck was it had a new  schraeder valve  installed. So the compressor was rebuilt. Then I saw that this guy had put a 134 adapter on the stem. So he had self diagnosed and added automotive 134-A with oil in system. At that point I told him the unit was bad and needed replaced. 

 

​Something that has not been touched here and is very important. Do not add refrigerant to a system unless you are qualified.  

 

​The information contained on this thread is intended to help diagnose a problem  to help save money it is not intended to by any means for you to recharge a system yourself.

 

Adding refrigerant to a bad system can cause bodily harm or a fire or even death. Adding to much can cause a fire. I have seen a compressor blow a hole out underneath the cap where your start relay and overload is and shoot fire out.

 

​The visual information here is very important and will help the unqualified know when he needs a professional. Breaking a line with hot refrigerant can and will blind you if it gets in your eyes. Refrigerant that is on fire is toxic and can kill you.

 

 

Leave the charging a system to the professional!  ;D  ;D 

 

 

Quoted for truth. I've been repairing vending machines for twenty two years now, and I lay off the refrigeration. I'm not qualified, and I know how dangerous the stuff can be. 

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These warnings should have been included in my post and I thank you for posting them.  This is why I did not post what any pressure readings should or could be.  I did not want to put enough information in my post so that someone could actually do the work without further investigation or training.  You are absolutely correct, this is work that must be done by a qualified refrigeration technician. 

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  • 1 month later...

Is frost like this always a sign of low refrigerant or could there be another cause such as . . . . .

gallery_6992_160_540773.jpg

  • an air leak somewhere
  • improper seal due to door not being sealed properly
  • bad or no airflow due stuff being placed around the sides of the machine
  • evaporator fan not working
  • machine too close to the wall
  • dirty/clogged condenser
  • something else I am not thinking of?

 

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From the above picture I wouldn't suspect low freon. The ice covers the accumulator and follows the suction line to the outside of the cabinet, You mention several things that are correct and those are a good place to start.

 

1 If machine is to close to wall heat builds beneath and migrates up. This cause the compressor to cycle more often and keeps the evaporator from drying out before each cycle.

 

2 Dirty condenser causes the same situation 

 

3 Bad cold control can also cause cycling to be to often

 

4 Door seals, Drain hose missing, air cap where lines come through cabinet,

 

I suspect the temp control on the above picture because the inside of the cabinet is very dry. Or evaporator fan motor. If there were a air leak I would suspect there would be more moisture inside.

 

All the above needs to be checked to make a correct assessment. Even if it ends up being low on freon you won't have any future problems.    

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