I'm attempting to do some DIY car repairs from my driveway, and need to remove the vehicle's AC condenser. To do so, I need to evacuate the r134a refrigerant from the AC system. Apparently it is the norm even at some auto shops to vent this refrigerant into the atmosphere, despite its high potential as a greenhouse gas and resulting legal penalties. I would like to avoid this method.

I've sourced a very old and very cheap Amprobe ProMax RG5000E refrigerant recovery machine, hoses and a tank for the job, and recycling service willing to dispose of it properly, and I have been studying the manual in preparation for the recovery. In doing so, I thought I might as well attempt the self-purge procedure, as I have no way of knowing what was in there before.

The self-purge operation results in a vacuum of ~10 in Hg after ~30 minutes, and doesn't seem to progress beyond that. It does seem to hold that vacuum for at least a half hour after closing the output and shutting the machine off. 24 hours later, the machine's vacuum seems to have returned to atmospheric pressure.

Does this mean the recovery machine has a slow leak? Is this machine still sufficient to perform a typical automotive refrigerant recovery, or will I risk venting a significant amount of refrigerant into the atmosphere?

  • Welcome to Motor Vehicle Maintenance & Repair! Dec 7, 2022 at 20:42

2 Answers 2


If your condenser coil is damaged, refrigerant was released and your system is most likely empty. Connect gauges to both service ports to see if any pressure remains. Designed as a refrigerant recovery machine, it's not a refrigeration vacuum pump. Recovering refrigerant is required following EPA regulations against releasing refrigerant into the atmosphere. In America, refrigeration repairs must use refrigerant recovery whether repairing vehicles or commercial hvac systems using large amounts of refrigerant. EPA fines can be substantial if businesses are found to deviate from recovering refrigerant, releasing it into the atmosphere. In practical terms, every vehicle with ac eventually releases refrigerant whether from a crash rupturing a system or service during repairs. Every ac system is considered sealed at factory assembly, refrigerant under pressure when ac isn't used. 98% of ac problems are leaks occurring from everyday driving. This simply means refrigerant escapes....... from damage occurring under normal driving situations. Refrigerant escaping from wear and tear or accidents isn't against the law. Deliberately releasing refrigerant into the atmosphere is, it's illegal if the EPA can verify it. A recovery machine simply removes refrigerant and oil mist to zero gauge pressure. In theory, only refrigerant is removed for possible reuse. Removing refrigerant is performed on undamaged systems. Damage resulting in a leak implies refrigerant is lost and any remaining refrigerant is recovered into a reclamation canister for proper disposal. A vacuum pump capable of evacuating a system down to 29.99 in Hg (near perfect vacuum) is one of several tools needed in refrigeration repairs. A recovery machine that cannot pump down to 29.99 in Hg won't perform and cannot replace a vacuum pump designed for evacuating a system. The recovery machine shouldn't be used as a vacuum pump if it cannot draw 29.99 in Hg. Refrigeration requires evacuating a system to remove all air and moisture in preparation for installing refrigerant. Air and moisture are enemies if allowed to remain in a sealed refrigeration system.

  • Despite frontend damage the AC system still has perfect pressure. The question was more so whether or not I should be able to count on this recovery machine to evacuate most of the refrigerant, before using an actual vacuum pump to get rid of what remains.
    – example6
    Dec 8, 2022 at 18:42
  • 10 in Hg is a partial vacuum and most likely good enough for removing refrigerant. Residual refrigerant 'boils' out of solution (oil) after recovery, showing up on the low side gauge as a creeping needle from '0' (or 10 in Hg). Unless you're familiar with refrigeration, you may be guessing on refrigerant amount as gauges don't state refrigerant amount. Only pressure. With ac off, r134a pressures will vary in almost direct proportion to ambient temperature; 75F/75 psi, 85F/5 psi, 95F/95 psi. Dye (greenish yellow) at factory assembly allows anyone with an uv blacklight to find leak(s).
    – F Dryer
    Dec 9, 2022 at 21:33

I'm not sure how testing would go, but would think you could plug whatever hose is there to withdraw refrigerant, then set it to evacuate, which should draw a vacuum. It should draw down to ~28"Hg in a very short time, then hold it. If it's not holding it, I'd assume it has a leak. If it's not getting to near complete vacuum, I'd assume there's an issue. You could also most likely put a self contained vacuum pump on the system with all ports blocked and do the same to check it.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .