My car AC compressor has blown 15 minutes after a regas/recharge. What could be the cause?

AC compressor has blown 15 minutes after a regas/recharge.

There is a high chance the system was working with a low refrigerant charge. It was a system performing poorly, but depending on weather conditions the driver wouldn’t notice a problem with the A/C system.

After the system was charged up to full capacity a problem with some restriction on the system or a fan clutch/radiator fan assembly would be more noticeable and would have enough refrigerant running in the system to open the high pressure relief valve and vent some part of the refrigerant.

An overcharged air conditioning system won’t hold more than a couple minutes before the pressure inside the system are high enough to open the relief valve and vent the refrigerant to the atmosphere.

A/C Refrigerant pressure controls


High Pressure Relief Valves

The high pressure relief valve (HPRV) is a blow off valve, designed to release refrigerant into the atmosphere if pressures get dangerously high. In an effort to keep refrigerants contained more efficiently, many manufactures have introduced controls designed to prevent pressures from getting high enough for the pressure relief valve to blow off. Single contact pressure switches simply shut the compressor down if pressures get too high.

The dual contact pressure switches have replaced most HPRV to prevent refrigerant venting to the atmosphere.

Fusible Plug

The fusible plug is installed on the top of the receiver/drier to serve as a safety device. The fusible plug has a special solder filled hole. If the condenser ventilation becomes poor and the cooling load becomes excessively large, the pressure in the high-pressure side of the condenser and receiver will become abnormally large and create a danger of bursting the equipment.

When the temperature and pressure in the high-pressure side reaches 427 psi and 200 to 212 °F the fusible plug melts and allows the refrigerant to discharge into the atmosphere thus preventing damage to the equipment (This will add to ozone layer problems)

Dual pressure switch

The dual pressure switch is fitted between the TXV and the receiver-drier. It detects pressure on the high side of the system and switches on the cooling fan(s) to high speeds and turns off the magnetic clutch shutting down the compressor when the pressure is abnormal, thus preventing damage to the system.

Low Side Pressure Relief Valves

Some R-134a systems use a pressure relief valve on the low side of the system. This valve is designed to prevent evaporator damage during system shutdown, when pressures equalize. The higher pressures in R-134a systems could cause low side pressure to rise beyond safe limits during system shutdown.

Low pressure cutoff switch

The low Pressure cutoff switch shuts the compressor down when refrigerant levels drop too low. Since the A/C systems use the refrigerant to carry lubrication, running the system without an adequate charge can cause compressor damage. This switch prevents the compressor from running when refrigerant levels are too low to provide enough lubrication.

High Pressure Cutoff Switch

Some vehicles have high pressure cutoff switch designed to shut the system off if pressures get too high. Once pressures drop back to normal, the switch will allow the compressor to operate as designed. Look for this switch on the discharge muffler’s service port, or mounted on the back of the compressor.

What causes an air compressor to lock up?


  1. Lack of lubrication
  2. Cooling system poor performance
  3. Condenser fan not working or performing poorly
  4. A/C system overcharged
  5. Incorrect type of oil
  6. Low refrigerant charge
  7. A/C system contamination(A/C refrigerant cross contamination (Charging R-134a refrigerant into R-1234YF refrigerant.)
  8. Inefficient condenser
  9. Dirty evaporator core (In the past, not much attention was paid to dirty evaporators. Technicians are now beginning to realize that low evaporator pressures cause high compression ratios.)


How to find an automotive compressor problem, before is too late?


Compression ratios are used to compare pumping conditions for a compressor. When compression ratios become too high, the refrigerant gas temperature leaving the compressor rises to the point that oil for lubrication may become overheated. Overheated oil may turn to carbon and create acid in the system shortening the life of the Automotive A/C system.


Ambient temperature

High Side Pressure


Low Side Pressure


90 °F/32°C      250-270 psi /1724-1862 kPa   45-55 psi / 310-379 kPa


Calculation example:

Compression ratio = Absolute Discharge


Absolute Suction




CR= 250 psig + 14.7 atmosphere


45 psig + 14.7 atmosphere




CR = 264.7






CR = 4.43:1




Understanding the A/C compressor compression ratio results.


A compression ratio of 4.43:1 would indicate to a service technician that the absolute or true discharge pressure is 4.43 times as great as the absolute suction pressure. Either an increase in head pressure or a decrease in suction pressure will cause higher compression ratios.


Symptoms of a Bad or Failing AC Compressor


Growling noise with compressor disengaged

Whistling noise

Grinding noise

Squealing noise

Rattling noise

Growling noise with compressor engaged

Banging noise

Knocking noise

How do I recharge the AC in my car?
Article Name
How do I recharge the AC in my car?
An overcharged air conditioning system won’t hold more than a couple minutes before the pressure inside the system are high enough to open the relief valve and vent the refrigerant to the atmosphere.
Publisher Name
Auto A/C Repair LLC.
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