A/C question


I purchased an older model BMW (E30) and cannot tell if the A/C has been converted or not. How can I tell? The system does not blow cold right now, and I want to repair it. If it has not been converted, should I do so? If not, what should I do to repair the system as is? Thanks


Can you tell by the connectors? Sometimes they put a sticker under the hood when the are converted.

I’m not sure about BMW, but my old benz did not perform very well with R-134a. I “converted” mine for a while, then I went back to R-12. If you use R-12, make sure you find all the leaks first, that stuff is getting expensive.


The older R12 systems and the 134 systems have different styles of fittings. The R12 has screw-on types and 134 uses a quick disconnect.

There are 134 adapter fittings that are generally used when converting a car and left in place on the vehicle.

If the vehicle has not been converted then I would do so.
You need to determine if the system is empty and if so, you have a leak(s). The most common leak is the compressor shaft seal.

If the system has been empty for a long time then the leaks need to be repaired along with replacing the drier and pulling a good vacuum on it before recharging.

Assuming you don’t have A/C manifold gauges check for system pressure by removing one of the service valve caps. Take a pen or matchstick and very quickly tap the Schrader valve in the service fitting. If nothing hisses or it’s weak then you have some leak repairs to perform.


Where did I say “vent”. The matchstick will be no worse than what happens when an A/C hose is unscrewed (R12) or quick-disconnected (134).


I didn’t make it up. The EPA did.

You should know it if you’re EPA 608 certified, or even if you aren’t.


You’re going to lose more refrigerant by connecting, and then disconnecting, the gauge set than you would by a quick blip of the ball point pen.
And that’s assuming there is even one molecule of refrigerant in the system; and I highly doubt there is on a 20-25 year old car.

I consider it normal loss during testing procedurers; all perfectly legal.
If I were doing it the gauges would go on it. The pen or matchstick is for the amateur at home who needs to quickly know if the system is tight or not.

Since you claim to be the A/C Pro-Extraordinaire, how about filling us all in on your years of automotive A/C repair. How many auto A/C schools? ASE are you?
How much in-shop practical experience on auto A/C?


You know STAR isn’t going to give you any history of his experience. He will just continue to post links to commerial A/C units that he never reads.

Willey, logged off again.


It’s not a technical issue, it’s a legal issue. EPA laws specifically exempt connecting, disconnecting, and purging hoses from the definition of “venting”. They do NOT exempt tapping a valve to check for pressure.
A minor leak will not change the static pressure enough for you to notice anyways. The pressure will only drop once all the liquid refrigerant has been lost. Once that happens, you know there’s a big leak that is easy to find.