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#1914435 - 06/05/10 10:45 PM Overcharged My A/C?
The Critic Offline


Registered: 08/30/04
Posts: 18782
Loc: Walnut Creek, CA
Have a '96 Saturn SL2 with the factory R134A system.

I professionally evacuated and recharged the system with the correct amount of R134A refrigerant (1.5 lbs) in June 2009.

Last week, in 70F weather, I noticed the A/C performance was mediocre at best. Given the 70F ambient temperatures and medicore cooling performance, the system was evidently undercharged.

So, I added [url=http://directory.pten.com/product/10103172/Interdynamics_Inc_Certified_AC_Pro_1st_Charge_with_ICE32]1/2 can of R134A[/quote]. At this point, the system was cooling well for 70F weather so I left it alone.

Today, we had a wave of warm weather. Temperatures were in the upper 80s, and I'm sure my car was over 100F after being parked in the sun for a while. The A/C system was again, mediocre for the 80F+ heat, but once the outside temperatures cooled down the A/C was working fine again. So, I added the rest of the can of R134A (for a total of ~11 oz) and the A/C seemed to be even colder (even though it was now nighttime).

It is very likely for the system to be slightly overcharged by a few ounces. At the same time, I am quite certain that I have a leak somewhere, so I'm sure it'll leak out. wink But if it doesn't, what kind of issues will a few ounces of overcharge cause?

Thanks!
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#1914443 - 06/05/10 10:51 PM Re: Overcharged My A/C? [Re: The Critic]
tomcat27 Offline


Registered: 06/25/09
Posts: 2961
Loc: Midwest
I overcharged an escort once. the pressure got so high it blew a fitting apart at the silver can looking thing. nice loud noise. nice dent in the hood.
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#1914445 - 06/05/10 10:52 PM Re: Overcharged My A/C? [Re: tomcat27]
The Critic Offline


Registered: 08/30/04
Posts: 18782
Loc: Walnut Creek, CA
Originally Posted By: tomcat27
I overcharged an escort once. the pressure got so high it blew a fitting apart at the silver can looking thing. nice loud noise. nice dent in the hood.


How much did you overcharge it by?
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#1914446 - 06/05/10 10:52 PM Re: Overcharged My A/C? [Re: The Critic]
spasm3 Online   content


Registered: 05/30/10
Posts: 6292
Loc: out there
Without using a gauge, you are guessing at the charge. Get a gauge.
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#1914456 - 06/05/10 11:01 PM Re: Overcharged My A/C? [Re: spasm3]
tomcat27 Offline


Registered: 06/25/09
Posts: 2961
Loc: Midwest
I only have an R12 gauge set and need to get one for R134. and whatever is coming next.
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#1914466 - 06/05/10 11:09 PM Re: Overcharged My A/C? [Re: The Critic]
JimPghPA Offline


Registered: 08/22/09
Posts: 3106
Loc: Pittsburgh,PA U.S.A.
If you already ran the unit and you did not slug the compressor with liquid and blow out a valve then it probably will never be a problem.

The main problem with over-charging is that if liquid gets sucked into the compressor the piston (or rotary vane, or wankel piston, depending on the compressor design) can not compress a liquid and will blow out a valve or damage something in the mechanical drive of the piston. This usually happens before you get the hood closed.

So if you ran it and it is still working then it is probably never going to be a problem.

Also you should know that most AC systems including most cars have a duel purpose section that is basically a large can or piece of pipe called an accumulator to hold extra charge and prevent liquid from being sucked into the vacuum side of the compressor. In most car system the accumulator is a duel purpose section also containing a desiccant that absorbs any small amount of moisture left in the the system after vacuum pumping it down so that moisture does not get to the orifice and freeze it up. Sometimes in car systems the material holding the desiccant breaks and the desiccant gets loose into the system and ends up clogging up the flow in the pipes, and or the orifice screen.

The fact that your car has an accumulator should let you forget about any problem of over-charging by a few ounces.
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#1914716 - 06/06/10 09:17 AM Re: Overcharged My A/C? [Re: JimPghPA]
Chris142 Offline


Registered: 06/05/03
Posts: 13886
Loc: apple valley, ca
Originally Posted By: JimPghPA


The fact that your car has an accumulator should let you forget about any problem of over-charging by a few ounces.
Actully his car has a very small reciever dryer and not an Accumulator.

Since the system is very small (1.5lbs) just a few ounces over charged will have an effect on it. I'm guessing 3oz would make the high side pressures go out the window.

But since he does not have a high pressure guage we do not know whats going on in there.
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#1914724 - 06/06/10 09:28 AM Re: Overcharged My A/C? [Re: Chris142]
onion Offline


Registered: 02/04/07
Posts: 2097
Loc: kansastan
+1 on what Chris said. That AC system is small enough that even a few ounces of over-charge can put the high-side pressure WAY too high. And being that it's a pretty cheap vehicle, there's likely no high-pressure protection switch to shut the compressor off in such a scenario (some automotive systems have this, lots of trucks and heavy equipment have it... but a small, modern, commuter vehicle like a Saturn probably doesn't). If you run the AC this way in hot weather, you're risking not only a blown hose or something... it could easily tear up the compressor.

If that was my vehicle, I'd evacuate the whole system and charge it with the proper amount. Anything else is just a guess- even if you have the proper gauges (though that would be a much safer guess).
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#1914769 - 06/06/10 10:24 AM Re: Overcharged My A/C? [Re: onion]
Cutehumor Offline


Registered: 12/10/02
Posts: 9364
Loc: USA
critic, are you on the original a/c compressor?
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#1914821 - 06/06/10 11:31 AM Re: Overcharged My A/C? [Re: Cutehumor]
mechtech2 Offline


Registered: 09/05/06
Posts: 19479
Loc: Chicago Area
R134a systems don't like overcharges. A bit low is better than a bit high.
Get gauges, or at least a low side gauge. You have no idea where you are at. Take static cold overnight tests, and running tests. Note the cycling pressures on the low side.

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#1914832 - 06/06/10 11:39 AM Re: Overcharged My A/C? [Re: Cutehumor]
The Critic Offline


Registered: 08/30/04
Posts: 18782
Loc: Walnut Creek, CA
Originally Posted By: Cutehumor
critic, are you on the original a/c compressor?

Yup.

One engineer once explained to me that the recommended charge is the ideal amount, and that there is a window of acceptable charges where the unit will still operate correctly. Is there any truth to this?

Of course, the best solution is to evac and recharge the entire system, which I think I'll end up doing anyway in the next few months to fix the leak. However, I remember that before I evaced and recharged the system in June 2009, the system was displaying similar behavior--- good performance when ambient temperatures are under 75F, mediocre performance in temperatures about 85F. And at that time, the system was about 1/2 lb low.
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10 Altima 3.5 - 34k - M1 EP 5w30/FU
92 Previa - 160k - Chevron 5w30/Wix

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#1914836 - 06/06/10 11:44 AM Re: Overcharged My A/C? [Re: mechtech2]
swalve Offline


Registered: 06/03/05
Posts: 588
Loc: Chicago, IL
If you are having cooling performance problems, check the condenser too- if there are a lot of clogged or bent fins, clean and straighten them. It makes a big difference.

You can feel the temperature of the liquid side of the system, after the condenser. It will be warm, but shouldn't be hot. If it is hot, the condenser isn't removing enough heat.

A perfectly charged system will generally be one that has the greatest difference between the high and low sides. All other things being equal. Too little refrigerant and it doesn't have enough high side pressure, too much and it can't pull the low side down far enough.

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#1914979 - 06/06/10 02:43 PM Re: Overcharged My A/C? [Re: swalve]
The Critic Offline


Registered: 08/30/04
Posts: 18782
Loc: Walnut Creek, CA
The strange thing is, I just went out to my car and powered on the A/C and it has never worked this well before. The outside temperature is in the mid 70s.
_________________________
11 Prius - 129k - M1 EP 0w20/OE
07 Accord 2.4 - 111k - M1 5w20/FPS Filter
10 Altima 3.5 - 34k - M1 EP 5w30/FU
92 Previa - 160k - Chevron 5w30/Wix

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#1915008 - 06/06/10 03:22 PM Re: Overcharged My A/C? [Re: The Critic]
onion Offline


Registered: 02/04/07
Posts: 2097
Loc: kansastan
Quote:
One engineer once explained to me that the recommended charge is the ideal amount, and that there is a window of acceptable charges where the unit will still operate correctly. Is there any truth to this?


Yes, this is true. And it can be a fairly wide range. A lot of OEM manuals will give a pretty wide range of acceptable high & low pressures according to ambient temperature. I think there's a fair chance that your charge will be within the acceptable range from what you've told us.

That said, it's only a guess- and you're still taking a chance. It's a chance I'd be willing to take if I hooked up a gauge set to it- both high and low, WHILE it's hot outside. But without making that check... I dunno.

I've seen a lot of compressor failures cause by overcharging: shade-tree mechanics just guessing where they're at. Even systems with a high pressure cutoff switch can be damaged this way- particularly if the condensor is dirty. High pressure=high heat=not a nice thing to do to your compressor.
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#1915740 - 06/07/10 10:42 AM Re: Overcharged My A/C? [Re: onion]
mechtech2 Offline


Registered: 09/05/06
Posts: 19479
Loc: Chicago Area
In the mid 70s, a car AC had better work well.

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