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I bought this car a little over a year ago and had a service shop charge the AC system. It takes 134a, but I guess some has leaked out since then. The compressor clutch won’t engage either. From my understanding of it, the clutch won’t engage unless it has enough refrigerant. How do I get the clutch to engage so that I can add refrigerant with this cylinder?
What have you done to check the A/C system? You say "some has leaked out." How do you know this? A/C not cooling as well as it should, or at all? What you really need to do is put a regular manifold gauge set on the system and see exactly what the pressures on the high and low side are. For all you know the system might be completely empty of refrigerant.
I don't think you can make the compressor engage until there is some minimum amount of refrigerant in the system. This is the whole point. The compressor will be damaged if the refrigerant level is too low, so that's why the interlock feature is built in to prevent the compressor from engaging if the refrigerant pressure is too low.
The best thing you could do is take the car to a local A/C shop and have the system fully discharged of refrigerant. Then get yourself a vacuum pump and a set of gauges and pull a vacuum on the system. You can find lots of youtube videos to show you how to do this. It is not difficult. If the system holds a vacuum, then you're good to go and, without allowing air back into the system, you connect your refrigerant cans and allow the 134a back to backfill the system. This will usually be enough to allow the compressor to operate. Start the engine, turn the A/C up to high, and continue to let refrigerant in from the cans until the pressures are where they should be, which you can also find out from the videos. There is probably a sticker on your A/C compressor stating how much refrigerant the system will hold, but that's for R12. I've read that the amount of 134a needed will be about 90% of the amount of R12 needed.
If your system will not hold a vacuum, there is obviously a leak, which you suspect, anyway. There are dyes you can put into the system which will show a leak under a black light, but I found the leaks in my system a different way. I pressurized it with air through the gauge set connections to about 40 or 50 psi using my air compressor, closed the valves, and then sprayed the various connections with soapy water using a Windex-type spray bottle. Wherever there was a leak, little bubbles would form very rapidly, so it was obvious. I tightened those connections, and all was good. I then pulled a vacuum for an hour or so to get as much moisture out of the system as possible as moisture is the problem when you let air in the system.
I found this video particularly helpful. It doesn't talk about leak detection, but you can find videos on that, too.
Great information! I’m completely unfamiliar with AC systems so I was just guessing that this was the same problem of low refrigerant level as before. When I hook my cylinder up to the low port it reads 25 psi, not sure where it is supposed to be. Would it be worth the expense of buying gauges and performing the tests you described or should I just take it back to the shop? I was hoping that if I could get the compressor to come on while the refrigerant cylinder was hooked up that damage to the compressor would be avoided
I don't think you need to worry about compressor damage, at least from low refrigerant levels, because it is self-protecting. You CAN'T make it turn on absent enough refrigerant pressure. Without the gauges, you don't really know what the pressures are. Refrigerant is added through the low pressure port, and if your system is reading 25 psi (is that with the system running?), that's not that low of a low-side pressure. But you don't know the high-side pressure.
If the system won't take any more refrigerant because the compressor won't turn on even though it seems like there should be enough refrigerant to make that happen, there could be another problem with the compressor that is preventing it from turning on. This would probably make it worth just taking the car to an A/C shop and let them deal with it. A gauge set and a vacuum pump together would probably cost around $150. That's not the cheapest, and you don't necessarily want to spend that much if you're not going to be servicing a/c systems regularly. If this is a one-off thing, then take the car to a shop. If you plan to work on this car as well as on a/c systems on other cars you have, even only occasionally, it might be worth getting the equipment and learning to do it yourself. But no matter what, as do-it-yourselfer, if you're interested in keeping to the law, you would still have to go to a shop to have the system drained of refrigerant if you ever need that before you take the system apart and service it. You're not supposed to just open the valves and let it leak to the atmosphere. It's one thing if it leaks out on its own because of a system leak. That's life. But you're not supposed to vent it to the atmosphere on purpose.
I did it myself. It's fun. My system had completely leaked out, so I didn't have the issue of getting it drained. I bought an o-ring set and went around and replaced the o-ring on every fitting. The two leaks I found were at fittings that I had replaced the o-rings, and I just needed to tighten them a little further. Then it would pull a vacuum and hold it indefinitely, so all was good.
I bought both the gauge set and and the vacuum pump at Harbor Freight.
April 10th, 2020, 09:17 AM
