Air Conditioning: Refrigerant (R134 or “Freon”) Loss (not due to system failure or leakage)

What it Does

Mobile air conditioning systems lose their refrigerant charge over time. In a well-sealed system, this loss is very slow (it can take years for performance to be noticeably affected), but it does occur.

Why This Matters

Loss of charge in air conditioning systems results in the system blowing warmer than desired. It can also contribute to mechanical failure due to loss of lubrication, which can increase repair costs.

Possible Problems and Concerns

Leakage (How does it get out?)

Let’s pretend that your vehicle had 100 molecules of a/c refrigerant gas put in it when it was manufactured. The gas goes into a system that uses a shaft seal (the compressor internals have to rotate so the shaft seal seals them off from the outside air), and this system also uses rubber o-rings to seal the different a/c components together. This is probably a well-sealed system! But those molecules are very small, and they do gradually escape. They’ll get past the compressor shaft seal and the crimp fittings where metal pipes and rubber hoses are bonded together. In other words, these modern systems seal very well, but they don’t seal perfectly.

Leakage Rate (How fast does it get out?)

Back to those 100 molecules: let’s say you buy the car brand new. By the end of year one, it has lost four refrigerant molecules. That shaft seal, the o-rings, and the crimp fittings do a good job, but between temperature changes, expansion and contraction, and vibration, a few molecules make their escape. At the end of year 1, you have 96 molecules left. In this condition, the system will not blow any perceptibly warmer or less efficiently than it did when brand new. Four more molecules get out each year. By the time your vehicle is nine years old, you’ve lost 36% of your original system charge. The air still cools, but it does not cool as well as it used to.

Wrong Understanding or Conclusions:

People bring their vehicles in for service when the a/c blows warm. And often this results in finding and fixing real leaks! But what about that nine year old vehicle mentioned above? What if there are no LEAKS, and the system is still sealing as well (or at least almost as well) as it did when brand new? The losses are small to the point of being imperceptible! There will be no u/v dye to find, no stray gas to set off leak detectors. The well-sealed (but not perfectly sealed) system remains a well-sealed system! Sometimes an a/c system that is blowing warm is not leaking. It has merely experienced normal refrigerant loss, over a period of several years, and a full charge will make it very happy for the next several years (assuming of course that actual “leaks” (the kind that can and need to be fixed) don’t develop within that time…

Higher Vent Temperature:

Loss of a/c system charge will impact comfort due to increase of vent air temperature. The loss of charge impacts the system’s ability to chill the air.

Slow Effect

The effect on vent temperature is often gradual. A difference of as little as 2-3 degrees can be an indicator that there is a problem, but this is not readily perceptible. (46 vs 48 deg F from the vent will feel very similar on the tip of your finger.) Length of time can also “hide” the problem. For example, if the system takes 25% longer to fully cool the cabin than it used to, this may never catch your attention. At least until that hot day when the system literally can no longer “keep up” and you start to realize that something is wrong. The system has been gradually getting less efficient over time, but it’s been such a slow and mild progression that you haven’t noticed.

Mild Symptom vs Severe Effect:

Many a/c systems are robust enough to still cool partially (or surprisingly well) while severely undercharged. But a severely undercharged system may fail to keep the compressor lubricated, and this can result in costly repairs. However, you may be unlikely to know that something is wrong, or (understandably) you may not think any more about it than, “I wish it blew colder, but it’s blowing cool enough that I won’t put money into it right now.” Perhaps you will want to service the system if you know that you’re reducing the odds of a severe failure versus just getting the temperature back down.

Loss of Lubrication:

A/C systems use refrigerant-compatible oil to lubricate the a/c compressor. Many systems will lose ability to keep the compressor lubricated if the refrigerant charge drops too low (oil is carried through the system along with the refrigerant circulation.) Loss of compressor lubrication can result in a failed compressor. This replacement comes with its own cost and also leaves the need to get the metallic debris out of the system. This commonly requires replacement of additional components or use of HECAT flushing equipment for debris removal. Either the way, the cost goes beyond replacing the failed compressor.

Compressor Clutch Failure:

An a/c system with a low charge will cycle a clutched compressor (if so equipped) more often. This is due to the low-pressure cut-off being activated. This works the clutch harder, and it wears more quickly. If the clutch fails, the compressor is unable to pump, and the a/c system cannot chill the air at all in this condition.