DIY AC Recharging Vs. Professional

[MarkV]

Well based on my recent thread about my Mark V and from what I have read I have low R-134a in my AC unit. So, should I buy a can of 134 and charge it myself? (the videos make it look easy) or should I take it to a professional? I have a feeling it was not fully recharged before or that it has a tiny leak as it blows cool but not cold and has done so for the past few months. Are the cans of 134a with gauge and o ring sealer good? What is your experience with them?

[Matt Harwood]

Your Mark V (or any of the cars in your signature for that matter) will use R12 unless it has been converted to R134a already. You can see whether it has been converted, as the conversion kits use blue and red fill and evacuation port caps, and like leaded versus unleaded gas, the nozzles are different sizes. If your car has not been converted to R134a, then the can of R134a you buy at the auto parts store won't fit and won't work.

The conversion is either simple or problematic depending on the car. The big thing is the seals, as the R134a molecule is smaller than R12, so it can leak out through seals that hold R12. The best conversions involve all new O-rings and often times a rebuilt compressor, but I hear that's not always necessary. I also believe the lubricants that are suspended in the refrigerant are different and not compatible, so a full system evacuation during the change-over is highly recommended.

There are probably kits out there that will let you just shoot R134a into an R12 system, and some places offer R12 "substitutes" but their efficacy is suspect. I personally have no problem with a conversion on a car, although performance may suffer a little bit, but I do believe that if you're going to do it, do it right to prevent headaches down the road. I'd consult an expert in this case.

[MarkV]

I had it put over to 134 about 6 years ago with a new compressor... It, however is obviously low enough to not blow ice cold air...

[MarkV]

I was thinking of using stuff like this:

Interdynamics California AF1CA - R-134a Refrigerant | O'Reilly Auto Parts

[Guest Kingoftheroad]

I was thinking of using stuff like this:

Interdynamics California AF1CA - R-134a Refrigerant | O'Reilly Auto Parts

Unless your experienced at charging ac systems, I'd take it to a professional you can trust. I've heard plenty of DIY stories that ended in damaging the ac system.

[avgwarhawk]

A truly charged system is one that is evacuated completely of refrigerant and moisture. Allowed to hold that vacuum for 15 minutes with use of a gauge to detect loss of vacuum which indicates a leak. A full charge and correct oil per oz pulled into the system by the created vacuum. Once done the system can be operated and both high side/low side reading confirmed as good. This can only be done with a machine designed to accomplish this task. Seek a trained technician and have it serviced in this manner.

[rhb1999]

Was the reciever dryer replaced? Will not be cold if system was opened up and it wasn't.

[Restorer32]

An a/c system doesn't "use" refrigerant so if the charge is low it has to be leaking somewhere. The dryer is critical and likely yours needs replaced. Save yourself a lot of headaches and have a pro do it. Call Classic Air in Florida first and they will advise you as to the likely problems.

[rocketraider]

Wes- I know it's expensive, but a professional is your best choice here unless you own a set of 134a charging gauges. They can read those gauges and tell whether the problem is a low refrigerant charge, plugged orifice tube or whatever other malady older, converted A/C systems can develop.

Rule of thumb is whatever quantity of R12 the system originally used, put in 75% of that amount 134a and system should cool adequately at highway speeds. That to me would entail removing refrigerant, vacuuming the system to 28"Hg for an hour or so, finding/repairing any significant leak, and recharging the system with the appropriate quantity of new or reclaimed refrigerant.

I'll say if you had it done 6 years ago and it's just now losing cooling capacity, you've done pretty well. It was generally accepted on earlier systems that they'd lose about a pound of refrigerant over a year, and that was with R12 that wasn't as prone to finding minuscule leak points as R134a.

But, like most things government science has a hand in, the results are always more regulations, more expense, more aggravation, and (often significantly) reduced performance- with little real benefit.

Edited June 20, 2012 by rocketraider (see edit history)

[rhb1999]

The EPA does not require leaks of R-134a to be repaired, only that the technician is licensed to handle R-134a, this why it's important tell the shop to locate and repair any and all leaks. It's believed that ester oil is less hygroscopic than PAG, and should used.

Edited June 20, 2012 by rhb1999
correction (see edit history)