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air condition compressor


rona's Avatar
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07-21-03, 06:38 PM   #1  
rona
air condition compressor

have 1992 dodge dynasty 3.3 6cly
changed from r-12 to 134 vacumn system changed dryer worked great for about 1 month now nothing- compressor will kick in but doesn't cycle-- correct pressure in system but no cold air--how can i check to make sure it is the compressor thats bad-even when compressor cycles the rpm doesn't seem to increase or speed up. Help

 
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07-21-03, 09:19 PM   #2  
if the pressures really are good---the compressor is good, that's it's only job, to pressurize.

correct pressure readings vary WIDELY depending on ambient temperature, humidity and especially on a system designed for a different freon(r-12) i refuse to do conversions in work because half of them come back to bite us, just like yours is.

some compressors back in that era were a non-cycling, internally variable unit, the only way we knew is what the parts dept told us, externally they look the same, either the h-valve was black or non painted(aluminum), depending on what compressor it was.

most likely you have a low freon charge, with r12 you could be way down and it would still cool sometimes. with r134, if it's down a little---you have no cooling.

what i'd do is recover what's left, add dye, then charge it according to the directions in the conversion kit, not by the r12 sticker underhood, they are different! when it stops working again in a month, you'll be able to see the leak.

if the suction line from the h-valve to the compressor is warm, most likely low on freon. if it's cold, the a/c system is working ok

 
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07-22-03, 03:46 AM   #3  
Joe_F
Correct.

Original poster: Please elaborate on the "system changed". What parts were changed in the conversion?

 
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07-22-03, 08:22 AM   #4  
As I've heard, when changing R12 to 134 all the hoses must be changed also. The molocules in R134 are smaller and leak through R12 hoses.

 
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07-22-03, 08:23 AM   #5  
Joe_F
Yup, as well as with alternative refrigerants/blends.

 
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07-22-03, 10:07 AM   #6  
Dan Meyer
As JoeF said, give us EVERY little detail as to what you did for the conversation.
As a rule of thumb, the high side pressure on a conversation should be 2.2 to 2.5 times ambient temp. Start at 2.2 and monitor vent temps.
There is no need to replace hoses when using R-134a. On some blends it is necessary - but a person shouldn't be stupid enough to use a blend anyway.

 
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07-22-03, 10:31 AM   #7  
Joe_F
Dan:

Not true. R134A WILL go through older hoses which were porous in nature and those that are in poor condition.

As for blends, I totally disagree. I used Autofrost in my Cavalier this weekend. I changed the receiver dryer, hose (which is 134A and 12 compatible) and all the O-rings.

With the fan on 3rd speed and MAX A/C it's like a meat locker in there.

Blends do work---depends on the system and condition of the same.

 
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07-22-03, 02:53 PM   #8  
Dan Meyer
Whoa, now you're adding "porus..... poor". In that case, even before recharging with R-12, the hoses should be replaced. But with hoses in good condition, R-134a shouldn't leak through.

As far as your luck with a blend, I can't argue with success.

 
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07-22-03, 04:28 PM   #9  
My cents.. From what I've read, heard and seen, there is a difference between the hose used for r-12 and r 134a. The new hoses are what's called "barrier hose". If you were to cut 1 and look at it, you'll see a "liner" on the inside, then the actual rubber hose material. The older hoses don't have this. The purpose is to contain the freon (r134a) as the molecules are smaller than the older r12..

Rona- As the others asked, what are the actual pressures, what was the origanal capacity, how much r134a did you put in, and what type of oil did you use? (and of course, how much oil?)
I've seen where too much oil will keep the car from cooling also..

 
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07-22-03, 05:02 PM   #10  
Again what do you see for running pressures? Those were known to have bad txv's. If you cant drop low side pressure than you cant remove enough heat to feel cold air.


As for refrigerant blends they should be outlawed. I have seen many systems with these blends that can only be serviced by who charged it. Shure they work fine but so does propane but you wont see anyone stupid enough to use that . Some manufactures do recomend changing to barrier hoses when retrofitting but some dont. R-134a is smaller and most retro kits have oil conditioner and leak sealer that seems to help with the pourus r 12 hoses. I have done many without changing hoses and no come backs yet.

 
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07-22-03, 05:44 PM   #11  
Joe_F
SDog:

Those KITS should be outlawed! There is no "convert" in a can for $35! Each car varies!

I will look at Alldata tomorrow if I have a chance. They have a VERY specific parts list for these Chryslers and what they recommend for changeover, by model. If Knuckles beats me to the punch, he'll probably post it.

(And he'll shake his head when he finds the bulletin to say, "Ah, here's the one Joe's talking about. LOL ).

MSA is correct. I just put new hoses in my Cavalier this past weekend. The hoses have a label that says "good for R12 or R134A". That is because the newer hoses will satisfy all previous requirements. Yes, the molecules are smaller in R134A and WILL eventually find their way out of a R12 old style hose.

Many people erronously believe that they must convert to R134A in order to have cooling. I would argue that, but it depends on the system and vehicle. Fords and Chryslers are not keen on blends, but GM's seem to like them. GM makes a great A/C system, always has. Nothing like the "log" (A6 compressor).

So far so good in my Cavalier. Meat locker on fan speed 3. Subzero on speed 4. EVEN COLDER on low speed with air pushing through on the highway. BRRRR! (less load on the evaporator).

I BELIEVE the old R12 hoses were that way on purpose to show oil type leaks when they occurred. A coworker and I were talking about this not long ago. I'll have to ask him to comment again.

 
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07-22-03, 07:36 PM   #12  
knuckles
Barrier hoses are required when retrofitting to R-134a. As Joe_F, mike in nj, and others have stated, the R-134a molecule is smaller than the R-12 molecule and can (eventually WILL) permeate a non-barrier hose.

Some people claim that the mineral oil used in older R-12 systems effectively coats the inside of the hose & creates a barrier that will contain R-134a. My experience has shown this to be total BS.

Chrysler minivans really DON'T LIKE R-134a. Their small condensor & ridiculous condensor layout leave VERY little room for error when it comes to charge amount. An ounce too much or too little=poor cooling.

As for blends:

Some, such as Autofrost, seem to work pretty well. However, they create a service nightmare as the EPA requires an a/c shop to have dedicated equipment for each refrigerant it services. Most shops will have equipment to service R12 and R134a as they were both used by the OEMs. Most shops are unwilling to spend $2-3k on a refrigerant recovery/recyclying machine for every blend that comes down the pike. Toss in to the mix that it is illegal for a shop to recover a blend & then dump it in to any other car than the one that it came from & you'll see why shop owners are reluctant to service cars with blended refrigerants.

Add to the fact that many DIYers improperly retrofit cars with blended or worse, HC refrigerants and fail to properly label & install the correct fittings & you've got a real disaster.

There's a huge debate both inside the a/c service & repair industry & among DIYers concerning blends and HC refrigerants. Both CAN perform amazingly well. Certain HC blends will outperform R-12 all day long, but with huge potential drawbacks. (BOOM!)

On top of the above, add the fact that most compressor manufacturers/rebuilders will only honor their warranty if R12 or R134a is used. Your warranty is void if you use anything other than an approved refrigerant along with the correct oil (mineral or PAG in most cases, though some rebuilders allow the use of POE oils).

Additionally, most expansion devices are calibrated for use with either R12 or R134a. They may or may not work well with a given blend.


With the above drawbacks and relatively few positives, blends don't make sense for me. I don't use them & don't recommend them as I can achieve a/c system performance comparable or equal to R-12 using R-134a.

Even the dreaded Chrysler minivan can be effectively converted if the condensor is replaced with either a larger universal condensor OR a late '80s/early '90s K-car condensor.

Certain cars, such as GM cars with variable displacement compressors, and most '80s/early '90s Hondas, don't retrofit well by design. In these cases (and they're getting rarer every year) I recommend repairing the existing system and keeping R-12.

FWIW, most older GM cars are great retrofit candidates. This is especially true of the RWD models. They have enormous condensors & require very little in additional parts to perform well with R-134a. The exception to this rule would be Cadillacs with ECC. They can be made to work well, but you have to rewire the ECC system to bypass the evaporator temp sensor & use an adjustable cycling clutch pressure switch in its place.

Please check out the following links before you decide to buy a blend. Note that EPA section 608 states that only certified technicians can buy blended refrigerants.

The EPA link cites all the rules. Note that your state may require a license to buy R-134a. Most states don't.

http://www.epa.gov/ozone/snap/refrig.../macssubs.html

http://www.epa.gov/ozone/snap/refrigerants/qa.html#q01

http://www.epa.gov/ozone/title6/609/justfax.html


http://www.epa.gov/ozone/snap/refrig...sts/mvacs.html

For opinions & retrofitting advice, see the following:

http://www.ackits.com/forum/categories.cfm?catid=3

http://www.aircondition.com/wwwboard/


Happy retrofitting. Or not.

 
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07-22-03, 09:12 PM   #13  
Joe_F
That's great advice. It does depend on the vehicle and the system.

Barrier hoses aren't cheap, and frankly, if the car is in poor condition, the last thing to worry about is the A/C. LOL. A good Delco hose with muffler can easily soak you for $100 if you buy at retail.

I'd agree with the fact of cross contamination except most of the vehicles we got to work on had already donated their refrigerant to the atmsophere (i.e. they had leaked out before they got to us). You'd see the tell-tale signs of oil on the hoses and what not and the bell went off in your head. LOL.

I'm pretty sure Autofrost is non-flammable. I know it has R22 in it and a blend of other things.

I agree with Knuckles regarding the "BS" statement. Most times, especially if it was a Chrysler, the metal part of the hose was so rotted and turned to dust that it would leak anyhow. LOL.

Safest bet: Change the hose(s), receiver dryer, orifice screen and update your O-rings to blue or green ones. That's what I did (along with a new pressure switch) and so far, so good .

 
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07-28-03, 11:33 PM   #14  
knuckles
more info on blends and additives

Tim at Arizona Mobile Air recently conducted a performance test of popular blends, additives, and refrigerant oils. The results of the tests are at the link below.

http://www.ackits.com/testresults/alttest.pdf

Autofrost fared pretty well. It probably works very well in Joe_F's car because older GM cars have enormous condensors that are exposed to lots of air.

 
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07-29-03, 03:51 AM   #15  
Joe_F
I guess my 1989 Cavalier must be huge by today's standard's .

It looks like a dwarf next to my 84 Olds 88 when they are parked next to each other.

LOL

 
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07-29-03, 09:22 AM   #16  
Back to original question...
Have you checked to make sure your vent controls are working properly. You may have a door stuck that is letting the fan air travel through you heater core.

Also, when changing to R134, the rule of thumb is to put in 85% of what is called for using R12. Too much R134 will make the discharge temp warm.

 
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07-29-03, 01:58 PM   #17  
knuckles
Joe:

The Cavalier condensor is big enough to run R-134a w/ no problems. I've done lots of 'em w/great results.

dirty dan:

85% is a rule of thumb, not a hard & fast rule. Some cars work best with 60% of the original R-12 charge, some work best at 90-95% of the original R-12 charge.

Anyone who works on an a/c system (whether retrofitting or not) should use a set of gauges. An overcharged system is very obvious, as both the low side and high side pressures will be too high.

The original poster said that there is the 'correct pressure in system', but never bothered to post actual gauge readings. Until we know what the gauge readings are, we really won't know if the system pressures are actually *correct*, and won't be able to offer any useful advice.

 
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07-29-03, 03:20 PM   #18  
Joe_F
Just drove home with the machinist at work and I asked, "Are you comfortable?"

He said, "Completely! Like a freezer in here" LOL.

 
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