Second in a Series of Occasional Posts on Shop Maintenance

Photography and Story by Jim Marotta


It's a sweltering August afternoon and an overheated customer comes in saying the A/C isn't working. Earlier this week you convinced him to pay for needed A/C system maintenance. What went wrong? Could it be deferred maintenance on your refrigerant recovery and recycling machine? Recovery and recycling machines have come a long way from their simple beginnings. However, with more complexity, there is more to go wrong.

Back to Basics

Surprisingly, basic maintenance on today's complex recycle/recovery machines has not changed that much. You still need to change the filters regularly and change the vacuum pump oil, if the machine has a vacuum pump. Also, you must purge the air from the tank. Draining the refrigerant oil recovery bottle after each use is a required daily maintenance task.

Changing the filters, O-rings, oils, and leak checking the unit can usually be done in about 1 to 1-1/2 hours with the parts costing under $100. Some machines will even prompt you when it is time for maintenance. Even the older machines use an hour meter that indicates usage between maintenance intervals.

When it comes to changing the filters, most are easily changed with common hand tools. Some even have knurled fittings and do not require hand tools at all. Changing vacuum pump oil is just as simple. While each manufacturer has a specified procedure, most are simply a drain and refill. Changing out the oil ensures efficient operation, reducing the amount of time the machine takes to evacuate the system. Another item, keeping a machine clean, is simply a matter of wiping up spilt oil or covering the machine to keep dust out of the electronic circuit boards.

Replacing a typical filter is a matter of loosening the tubing nuts and replacing the filter. Photography by Jim Marotta.

With repair bills for recovery/recycling machines averaging $400 and up, and the cost of a new automatic machine averaging $2500, plus the lost revenue from the absent machine, you can see that maintenance is the answer.

Common problems and failures

  • Oil drain bottle is not drained after each recovery - If the oil bottle is not drained and allowed to fill up, it will allow liquid refrigerant to enter the compressor. The compressor is made to pump gas and when liquid is allowed to enter the compressor it will damage the valves. The only repair at that point is to replace the compressor.

A twist of the wrist after each service keeps oil from building up and causing damage to the machine. Photography by Jim Marotta.

  • Air in the refrigerant - When air finds it way into your storage tank it can be troublesome: it can shut the machine off due to excessive pressure and slow down the recovery process. You can tell if air is present by comparing the pressure and temperature in the storage tank to the manufacturer's table. Follow the manufacturer's instructions and purge the air regularly; you don't want air in your customer's A/C system and you don't want it in your recycler.
  • The machine is left dirty or dusty - Keep it free of dust to protect the circuit boards in the machine. Too much dust can cause the circuit boards to short circuit and fail. Some of the boards are $500 to $800 just for the part.

A buildup of dust on circuit boards may cause them to short circuit and fail. Photography by Jim Marotta.


Dirt drawn in through the compressor air intake will eventually cause accelerated wear on this unit. Photography by Jim Marotta.

  • Tank valves leak - When you have a tank valve leak it is usually due to overtightening or overopening the valve, which damages the valve seats. The tanks are required to meet DOT certifications and if a valve is replaced in the original tank or if the tank is older than five years send it out to be recertified, just like a welding cylinder. The cost of a new tank is most often less than or about the same cost of replacing the valve and sending it out or recertification. You can get a new tank on the machine a lot quicker.

Excessive force when closing a service valve wears out the valve seat, causing the valve to leak and refrigerant to escape. Photography by Jim Marotta.

  • Hoses and O-rings leak - Inspect hoses regularly and replace them if they are bad. If working with pressure in the line, the refrigerant will most likely leak out like air through a leaky fitting on a shop air fitting. However if you are working with vacuum in the lines you may experience the symptoms of a compressor or vacuum pump failure. Symptoms include the unit not pulling down adequately. If the machine is in recovery, this will fill your recovery tank with air pressure and eventually should shut the machine down.

Why replace O-rings? Take a look at this comparison. The one on the left is new. The one on the right is swelled and could allow refrigerant to escape or air to enter the system. Photography by Jim Marotta.

The other common problem with O-rings, and this one is much more overlooked, is people tend to overtighten the hose connections especially when the O-rings have deteriorated and are in need of replacement. This causes the O-rings to over-compress and seal off the flow of the hose, resulting in slow or no charging, recovery, and evacuation depending on which hoses are affected.

This is not a reliable seal under pressure or vacuum. Under pressure refrigerant will leak out and under vacuum air will leak in. Photography by Jim Marotta.

Another byproduct of overtightening the O-rings and not replacing them is that small pieces of the O-rings may break apart creating fragments which tend to get stuck in the valve cores and solenoids causing recycler malfunction.

  • Keypads fail - Keypads will wear out with use, but take care not to use screwdrivers or other items to push the keys.
  • Scales require calibration - Overcharging or undercharging a system usually results in a comeback and a hot, angry customer. Calibrate the scales frequently.


Save yourself the aggravation of comebacks caused by neglected maintenance of your recovery and recycling machine. Good tools, available when you need them are essential to your professional image and your business. Don't neglect your service information. Subscribe to ChiltonPRO and access the information you need when you need it. For those who only need information on only one or a few models, ChiltonDIY is available.


A muscle car enthusiast and drag racer, Jim Marotta is a freelance automotive writer with more than 20 years experience in the automotive industry.