Overcharged AC

Well, at least I hope you learned not to do stupid things that you don't know about.

Of course, if you need more R134a, it is because there is a leak someplace. The proper fix is to find the leak, fix the leak, and then refill the system using the proper equipment.

Jeff

Jeff

I am pretty familiar with the workings of cars, and I do not mess with the refrigerant charge in my cars because I do not have the proper equipment, and the price of a repair is way higher than the money I would save by hoping to get lucky. Pros call those little cans of refrigerant "suicide cans" for a good reason.

I am not sure, but I suspect that the instructions on the can warn not to vent refrigerant (134-A is not "freon") into the atmosphere. Doing so is environmentally unfriendly, is subject to a large fine if you are caught, and can cause frostbite and permanent eye injuries if you are not wearing proper eye protection.

You are probably lucky and probably have not caused any permanent damage to the AC system. The smart thing to do at this point is to take it to a shop and have the high and low side pressures checked.

On Jun 12, 3:03 pm, SQ wrote:

Probably not if it's working normal again, but you may have blown some oil out when you punched the valve. The best indicator overall is a sight glass. But... Some cars don't have sight glasses. So you have to go by feel and pressure. The usual best indicator for charging with no glass is the drier canister. You look at the sweatback, or ice if really undercharged. Usually, if it's low, the canister will only partially sweat. When charging, charge slowly until you get a complete sweatback on the canister, and no more. !!! It's not exact, but usually good nuff fer gov work if no glass, and no gauges. If you noticed a lot of oil all over the place after you dumped the charge, you might want to put some more back in. But if you didn't see much oil, and the compressor is not making valve noise, I probably wouldn't add any. Too much oil is bad, just like too much refrigerant. Many people think mo is better, but when you overcharge, all you are doing is raising the evap coil pressure, and thus temperature, and you actually cool worse. You also run a high head pressure, which is no beuno. You were probably tripping off on a high pressure switch which probably saved the system. You can also flood the compressor with liquid. No beuno.. The suction pressure with R-12 almost is linear with the coil temp.. Not exact, but fairly close.. IE: 32 degrees "freezing" = about 31 lb's of pressure. Normally, you want about a 40-45 degree coil temp. You can run it colder, but you risk blowing fog in humid weather and possible icing. If your pressure goes up by overcharging, the evap coil temp rises pretty much in tandem with the pressure. The coil temp vs pressure scale of 134a is probably slightly different, but close nuff for gov work.. I agree with some.. A/C systems are not a good thing to work on, if you don't know what you are doing. The repair of a molested unit can be big $$$$$.. But, on the other hand, charging a system is not rocket science, and it can be done at home, under the clinical supervision of a doktor.. You just need to study up a bit first.. Anything past charging, I don't recommend doing unless you really know what you are doing and have all the tools. I also don't recommend recharging totally empty systems unless you have the tools.. IE: need a vacuum pump.. And even then, if it's totally empty, you need more work, so no point in recharging anyway.. It's just gonna gush back out. BTW, you don't need a EPA ticket to buy or handle 134a, as far as I know, but you do to use or buy R-12. You are not supposed to even put gauges on a R-12 system unless you have a EPA ticket. Anyway, enough of this novel.. BTW, I don't work on car A/C's, but I do work on residential HVAC. So I halfway know what I'm doing even on cars, and I do have all the tools.. I also have a universal EPA ticket.. I've passed all 5 tests, including the "auto can" ticket.. So I'm legal to work on anything. MK

Thanks for the info. A DIY repair can surely turn into a disaster, I will take it as a learning experience. Be glad that the compressor still works and not do it again. The over the counter recharge kits are too crude, I am not sure their gauges are right. Although mine was showing "Warning" when the compressor was cycling every few seconds. I was able to get it down to the blue zone which was OK.

The AC works much better than when I started and somewhat better after the first charge. I think it's probably as good as it gets with this vehicle. I also noticed that it seems to be a bit colder when driving vs. idling.

That is normal. In fact, you should always raise the rpm up to 1500-2000 or so when charging. If you don't , you won't see what the system really pulls down to at speed. Could end up undercharged if you went by pressure alone at idle. At idle, you might be pulling down to say 50 lb's, but if you goose the rpm's up, you could pull on down to 20 or 30. If the pressure drops too low at speed, you can fog and ice up. Another reason it gets colder at speed is you have much more cool air being forced across the condenser coil, which drops the head pressure. Much more efficient transfer of heat with all that air moving across the coil vs sitting still with a puny 12v fan moving all the air. If you charged the system, and think it's fairly full, but still lackluster cooling, you probably have a slight restriction in the metering to the evap coil.. IE: semi clogged orifice tube, funky expansion valve, etc.. Also note that the vent temp might only be 15-20-25 degrees above ambient temp. So if the air in the car is 90, you might only see 65-70 degree air come out the vents. But as the car cools off, and the ambient temp drops, the air from the vents drops also. So by the time it's

75 in the car, the vent air might be 50-55f.. This is why they seem to work so well at night... No sun load, and the car cools down quick, which will give you cold vent temps once it does. After a while, you'll see condensation on the windows near vents if it's humid outside.. On my honda, it likes to condense on the windshield, from the front glass vent.. The other night I saw the corolla grow water on the side window glass..

sides of the dash I think.. Thats where most of it seemed to be.. MK

MK,

Thanks for sharing your expertise.

I guess I've been very lucky for 10 or 12 years now, because I've recharged several cars with both 12 (freon) in the old days, and now 134, and have only overcharged the system once. I quickly vented the excess 134 and the compressor started running correctly. I have never felt threatened by the possible explosion of a can of the stuff, and due to the difference in valves, it's not possible to infuse the can's contents into the wrong side of the compressor. But I guess in future I'll defer to Ray and take it to an a/c shop.

Or, invest in a set of manifold gauges.

This is just my opinion, but using those suicide cans is like smoking while filling up your gas tank or having unprotected sex with strangers. There was a guy whose job at the port of entry was to put 2 gallons of gas in every car. This guy was a chain smoker, and he never blew up, but even so, smoking while fueling a vehicle seems unsafe to me. It is possible to get away with a dangerous activity for years with no problems, but there is a pretty good chance that the odds will catch up. With the proper training, equipment and protective equipment, re-charging an AC system is a perfectly safe operation, but if one of those 3 key ingredients is missing, then it becomes risky.

So, breaking this into "danger categories", what are the risks to the car itself, and the do-it-yourselfer trying to recharge an AC system?

The only way you will shred a can is hooking it up to the high side. And most high side connnectors are a smaller size, so it won't fit.. Sooo..On most cars there is usually no way to go wrong. But you should still always double check that you are actually on the suction side, which is usually the fatter of the two. Most low side connectors are near the drier canister area in general. Using cans doesn't bother me in the least bit.. But.. I don't hook them up to the high side... :( Good way to ruin your day.. The corolla I have is the first car using 134a that I've had.. My accord uses R-12.. I still have a nearly full 30 lb drum of R-12.. I'll probably never use most of it.. Probably should hawk it off on fleabay for $$$ $.. The price of R-12 really went through the roof.. I'm kind of afraid if I kept it too long, the demand might drop off, and not be worth as much. R-22 is starting to crank up too, being it's being phased out. I was buying 30lb's of 22 for about 60 bucks last year. Now it's 95-115 bucks per 30lb's depending on where you go. BTW, those are wholesale prices... Will probably get worse next year.. MK

What should it cost (doing the work yourself, buying a small can) to completely refill something like a 96 Camry's AC system?

Risks to the car:

- overcharge ruins the compressor or bursts a line or component if the high pressure switch is not working properly\

- charge without using the proper quantity of oil ruins the compressor

- the root cause of the low refrigerant level is not fixed so the refrigerant keeps leaking out and you waste money

Risks to the do-it-yourselfer

- frostbite

- eye injury

- burst can (the risk is very low because you would have to work to hook it up incorrectly)

The risks to the car are greater than the risk of injury, and I am cheap so I would rather pay someone to charge it correctly than pay someone to replace a part I screwed up because I do not have the correct tools and than charge it correctly. I try to invest in tools from a cost-benefit perspective. The cost for the gauges, vacuum pump, etc. to properly service an AC system is a lot more than the $50 I spend every 10 years or so to have my AC system charged.

I agree with the tool investment strategy. Now: A mechanic who's been accurate and competitive with other repairs over the years says a recharge is $125.00, assuming no other problems. Outrageous? (96 Camry)

No. (The $50 number I pulled out of my behind shows how long it has been since I've paid to charge an AC system).

$50 I wish. My old 1989 Trooper A/C is lacking in cool and I called a couple places today, they said to just to bring it in, they would have to change it over to R134 (it has R-12) and recharge=$200, then look for the problem of why it is not cooling, more $$. One place said it could cost anywhere from $200 to $1500, yikes!! That's more than the old bird is worth. I do have a few cans of R-12, but I don't really know much about A/C and repairs so I like you would rather someone else do it, but the cost is too much. How are these retrofits to R-134, any problems?

Those cans of R-12 are worth quite a bit to someone with the license to handle it.

Those R-134 retrofits are great, there are few problems these days from reputable shops. I would do the conversion if it were my vehicle. Fortunately, they all take 134-A!

My air conditioning guy suggested rebuilding my '92 Corolla R12 system with R12 even though the refill would be more expensive.

He got a new Denso compressor and replaced the receiver/dryer, evacuated the system and refilled with R12.

It works great.

He said I would be MUCH happier with R 12 and I am.

Thats true. Most R-12 systems converted to 134a will run higher head pressures. The condensor coils on R-12 systems will usually be a bit small for conversion to 134a. So you end up with higher head pressures, which then means you usually need to slightly undercharge in order to keep a decent suction pressure. The system just doesn't work as well. This is why I stocked up on R-12.. I prefer to keep R-12 systems as is.. Modern 134a systems are designed to get around these problems with larger condensor coils, etc.. So they do quite well in general. The R-12 system in my honda still works great. When I got the car, it was empty, and I assumed it was probably toast.. But I got lucky. All that was wrong was a loose shrader valve stem, which I tightened and recharged. I was expecting it to leak some, but it didn't.. It was all leaking out the low side service valve, which had a cap with no o-ring seal. :( MK

My old 89 Trooper is a town car, just short trips to work of about 6 miles on city streets. When she retires in about 5 years we will downsize to one car. So my question is how much did it cost for the work you had done, if you don't mind. I have fear the compressor seal is leaking and that means a rebuild or new compressor, expensive? I think it is also a Denso brand.