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Low cooling/shop's advice
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Steveg
Novice
May 10, 2007, 9:27 AM
Post #1 of 10
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Low cooling/shop's advice
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I brought my car in, a 1991 Dodge Colt, to service the (aftermarket) air conditioner. The AC was cooling, but I thought it was less efficient than it should be. The shop said it was outputting air at 60 degrees Farehneit, but it should be 50 degrees. The shop said the unit was shutting off after 5 minutes, and then starting up again (?). They said a replacement compressor and dryer were required. On the receipt the shop marked high and low figures of 265 and 55 respectively. I don't know what this means. I am wary of the shop's recommendation. I would appreciate advice and comments about what may be occurring with my AC unit. Thank you. Steve
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
May 10, 2007, 12:28 PM
Post #2 of 10
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Re: Low cooling/shop's advice
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Output and pressures seem a bit high. What was the temperature when these were taken?
It could be fairly normal for an aftermarket system unless this is a new concern. Try misting the condenser with some water and see if your output temp really drop dramitically. The fan may be inadequate to do better than that for the condenser.
If system is quiet and it has always performed this way it might be normal for that aftermarket system. I wouldn't blame the compressor at this point without some more info. Could also be slightly overcharged?? Has anyone messed with it in it's history that you know of?
T
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Steveg
Novice
May 10, 2007, 12:50 PM
Post #3 of 10
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Tom: Thank you for responding and your advice. I'll give the "misting" idea a try. The unit was once serviced by a shop many years ago. I had not noticed any particular problem, though I was vaguely aware of a fall-off of cooling power. No freon added in many (10?) years. It was a warm day (above 90) in San Diego when I had the unit looked at. The system is quiet. The invoice says that 20 ounces of freon were recovered when I first brought the unit in to be looked at. The shop person said the unit takes 1 1/2 pounds of freon. I have no idea.
I may have to spring for another diagnosis at another shop.
Steve
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
May 10, 2007, 3:41 PM
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You said the shop recovered 20oz and system holds 1.5lbs. If that's accurate you are low about 4oz but those pressures don't indicate that. High side can run about 2.2 to 2.3 times the ambient temp. Those are guidlines not necessarily the goal to achieve. However if you car had ambient temp which is the temp right in front of the condenser of let's say 95 X 2.3 = roughly 220. More refrigerant would raise the # with all things working properly.
The misting the condenser is a great way to cool it even better that the fan can and if the condensed refrigerant is cooler it has a lower pressure and is capable of making more BTUs at the evaporator.
If this system didn't take any refrigerant in 10 years it's really holding well. The evaporator and condenser over the years have no double built up some dirt and won't exchange heat as well as when new which is somewhat normal. You can clean the condenser easily but unless you really think it needed I'd leave the evaporator alone.
The ductwork almost couldn't be as good as an original system and the fan up front may not have been improved over a non A/C car's system so you would expect the aftermarket to be less effective than an original. There are some real good aftermarket systems today being sold that come real close.
I'm just wondering if you have a real problem or not. The mist test you can do and you should get a wired indoor outdoor digital thermomer for car or home use for under 10 bucks and do a lot of diagnosing on your own with just that.
If this system is R-12 that is good for efficiency and should be kept R-12 if at all possible in this case.
It sure seems like this was a pretty tough aftermarket system,
T
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Steveg
Novice
May 10, 2007, 5:40 PM
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Tom: Unfortunately, my reading of the invoice turned out to be incorrect as to how much freon was recovered from the system. I visited the shop, and the repairman set me straight. He said his handwriting (scribble) was the problem, and pointed out that only 7 ounces were recovered from the system. He said he replaced 9 ounces. So, the system is indeed low on refrigerant. It is still cooling down to about 59 degrees at the cabin outlet.
A question is whether the repairman, having decided I needed a new compressor/dryer, missed the obvious that the system just needed freon. However, this is entirely speculative on my part. I do not know what he did as part of his diagnostic procedure. He said the compressor shut itself off after 5 minutes (and then turned itself back on), though cool air still is being blown into the cabin. I am not particularly aware of the compressor shutting off while driving, and I am not experiencing this as a problem.
I think my best bet is to get a second diagnostic from a shop known to specialize in auto air conditioning. My car was serviced there before many years ago. This is in deference to my having only thumbs on my two hands.
I appreciate your sharing your knowledge and advice.
Steve
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
May 10, 2007, 7:43 PM
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I agree with getting a shop that specializes or at least does a lot of A/C work. The pressures you mentioned just don't line up with that low of a charge so something is screwey about that diagnosis.
Let us know how you make out. It would be good to get this fixed soon as running low on refrgerant hurts the compressor because the oil is moved by the refrgerant,
Stay cool,
T
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Steveg
Novice
May 10, 2007, 8:48 PM
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The car is due in the shop on Tuesday. I'll report back.
Thank you.
Steve
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Steveg
Novice
May 15, 2007, 4:59 PM
Post #8 of 10
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Tom: I visited another air conditioning shop today for another diagnostic. It was the right thing to do. They found that the condensor fan was not working. I missed that. (I saw that the engine fan was working, confused it with the condensor fan, and didn't look further). The inoperative fan accounts for the unually high pressures which you recognized during my earlier posts. They also found a front compressor seal leak. Apparently this is a slow leak, as they thought it feasible to fix the fan, and then periodically replace the freon. However, the car is still using R-12. They recommended a retrofit to R-134.
Their cost estimates for repair are (1) compressor job, retrofit to R-134 and fan repair - $1250, (2) Retrofit to R-134 and fan repair - $450, and (3) Fill with R-12 and fan repair - $500.
I have made no decision. The car's age leads me to take my time. I am wondering if I can handle a fan repair on my own. I'm not counting on it. I also wonder whether a chemical "stop-leak" is verboten.
If you would like to comment, I would appreciate learning your views.
Thank you.
Steve
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
May 15, 2007, 6:27 PM
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Sounds like good news. You could fix the fan yourself if you have some tools. That may require removing several items to get the rack of it out. If it's the type that must go down to get out consider that and how high can you get the car up. Also note!!!!! Many electric fan motors have a nut that holds them and they are left hand threaded and rather handily snap right off and cause severe use of bad language!
Just so you know and this is wholesale pricing for 30lb bottles of refrigerant: At last check virgin grade R-12 is about $600 and virgin 134a is just under $200.
Also ---- sealers can work but won't work on a shaft seal - period. I don't suggest using them and none that I know of are for R-12. Don't mix things up it's not legal and it can mess up what is still good in the system.
Find out how long a boost lasts with R-12. It may go a year. My chart says 91 colt hold 36oz of R12 from empty. They will lose cooling by about 1/3 low and total loss by half full. The math 30lbs is 480oz and would be about $40 bucks at cost for a 1/3 boost plus markup and labor to do it so perhaps $80 for a boost. If it needed that very often it's nuts not to fix the leak. If you convert you may be asked or told that the hoses are not barrier type and they must be replaced. It's true that the old hoses can leak thru the rubber if they are new but if they are old and used and not leaking now they usually don't so you can roll the dice on that one.
As you know R-12 is restricted for sale so it will be near impossible or impractical to buy it in 30lb containers as you would never need that much. They used to sell 14oz cans of it but they are scarce as chicken's teeth and you still need some equipment to add only the correct amount and the little cans will just lose the rest as the taps aren't that tight. This would be more practical to just pay a shop to do for most people. R-12 is almost extinct so I wouldn't keep paying for it for fast leaks and many shops just don't deal with it anymore at least around me.
Good luck with the fix,
Stay cool,
T
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Steveg
Novice
May 15, 2007, 10:15 PM
Post #10 of 10
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Tom: Thank you. I appreciate your comments and advice.
Steve
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