Why does car a/c always seem to fail?

[Chad Hauris]

I have a collection of cars and trucks from the 70's and 80's and early 90's (3 Grand Marquis and a Dodge van) and the air conditioning has quit on every one. Had 3 compressor seize-ups and 1 with bad seals. One of these cars, a 78 Grand Marquis has over 240,000 miles on the engine but the AC compressor clutch seized and the compressor is non-functional. The 90 and 91 Marquis AC was working but quit after about 100,000 miles. Just about every old car I have looked at at car lots has the AC compressor bypassed with a shorter belt. Why can't they design these systems to last a little longer?

It's not so bad when the alternator, power steering pump or starter goes, you can replace these yourself for around $50, but all quotes for repairing AC seem to be around $1,000.

[skippy_ps]

Junk yard for compressors or maybe a rebuilt one. Clutches are usually not too tough to replace and iirc are around $100 or so for U.S. autos.

Rig up an evac pump (this is a must) from an old refrigerator compressor and let run for at least 30 minutes. Hook a hose to the output and stick in a jar of water to see how bad the leaks are. :worried:

Gauge set is a must also. Probably can rent or borrow.

Ain't auto repair fun!

Murray

[LBPete]

Chad, The basic shortcoming of those old AC systems is leaks. It is very hard to keep the refrigerant from leaking out. Many of the AC systems from the 60s and 70s were installed in the dealership after the car was made. I installed a lot of them in the mid 70s.

Some of the cheaper kits were so crude that you had to cut the hoses to length and install a hose end held in place with a hose clamp. The other factor working against you is the refrigerant, R12 is hard to contain. It will actually seep through the hose itself. As greenhouse gasses became an issue in the late 80s and early 90s, car manufactures had to line the interiors of the A/C hoses with special material to make them less porous.

The lubricating oil for the compressor circulates with the refrigerant. It leaks out too which results in the compressor failing. That often causes a lot of debris to be in the system. If this debris is not completely removed, it will cause replacement compressors to fail which adds more debris causing the next one to fail sooner.

There is also the affect of air and moisture in the system. It combines with the refrigerant and oils to form acids. You can imagine what that does to your compressor. Now we can talk about the quality of the replacement compressors. There is a lot of crap on the market that may not last even if the rest of the system is perfect.

Are you getting the picture? Now for the good news. The AC systems for the past 15 years or so are much better and will last a long time as long as the charge is maintained. If you want to get an old A/C system working, you pretty much have to either remove and clean, or replace most if not all of the components including the hoses. For that mater, the old rubber hoses probably should always be replaced. You mentioned $1,000. That sounds about right.

- Pete

[SolderIron]

>refrigerant, R12 is hard to contain. It will actually seep through the hose itself

I didnot know this. Learned something new today.

>often causes a lot of debris to be in the system

I always think the dryer has a filter inside to trap debris. Maybe I am wrong. :scratch2:

[skippy_ps]

Yep, it was common in the R-12 days to add a can (about 1 pound) or 2 every year. Used to, you could buy these little kits of R-12, a can tapper and short hose for a few bucks. R-12 by it self was about $1.50 or less a can.

R-12 is supposed to be entirely phased out soon. Most folks just put R134a in although there used to be/still are stories about it not being compatible with R-12 oil or whatever. I've done this (put R134a in a R12 system) and it works. YMMV.

Murray

[tentoze]

My company car (a 2000 Chevy Lemona) just got a new compressor today. With an oil change, $770.35 from Mannie, Moe, and what's-his-name.

[hpsenicka]

Yep, it was common in the R-12 days to add a can (about 1 pound) or 2 every year. Used to, you could buy these little kits of R-12, a can tapper and short hose for a few bucks. R-12 by it self was about $1.50 or less a can.

R-12 is supposed to be entirely phased out soon.

I'm pretty sure I still have one of those kits somewhere in my garage... might even have a can or two of R-12!

Has probably been there 10 years... does R12 have a limited shelf-life?

[Big Dave]

To answer a few questions...

R-12 and R-134A are INCOMPATABLE. To convert an R-12 system to an R-134A system the oil must be removed and the lines and coils flushed. There are different connectors and gaskets involved. 134A uses a different oil. Mixing R-12 and R-134A will eventually kill your compressor.

To vac down a system, you MUST have a guage set, micrometer and a vacuum pump. You must get a vacuum of about 450 MICRONS. When the micrometer reaches that point, close the valve on the vac pump. If there is still moisture in the system, the micron reading will rise. Restart the vac pump and let it pump some more. It will take about 30 minutes minimum to get to that level. Moisture in the system will cause the refridgerant to turn acidic, compressor killer.

What looks like a filter-dryer is really a suction line accumulator. It holds any liquid refridgerant that comes from the evaporator (inside coil). Since there are more vairables with car A/C than residential A/C (especially no filters), the car A/C is more suseptable to slugging (liquid refridgerant hitting the compressor intake). Slugging will kill a compressor.

If you reuse a known good compressor, replace the clutch and ALL gaskets. replace the gaskets if the system has to be opened for ANY reason.

[nevermind]

To answer a few questions...

R-12 and R-134A are INCOMPATABLE. To convert an R-12 system to an R-134A system the oil must be removed and the lines and coils flushed. There are different connectors and gaskets involved. 134A uses a different oil. Mixing R-12 and R-134A will eventually kill your compressor.

To vac down a system, you MUST have a guage set, micrometer and a vacuum pump. You must get a vacuum of about 450 MICRONS. When the micrometer reaches that point, close the valve on the vac pump. If there is still moisture in the system, the micron reading will rise. Restart the vac pump and let it pump some more. It will take about 30 minutes minimum to get to that level. Moisture in the system will cause the refridgerant to turn acidic, compressor killer.

What looks like a filter-dryer is really a suction line accumulator. It holds any liquid refridgerant that comes from the evaporator (inside coil). Since there are more vairables with car A/C than residential A/C (especially no filters), the car A/C is more suseptable to slugging (liquid refridgerant hitting the compressor intake). Slugging will kill a compressor.

If you reuse a known good compressor, replace the clutch and ALL gaskets. replace the gaskets if the system has to be opened for ANY reason.

Absolutly right. :yes:
Compressors with R-12 use mineral oil,and the ones with R-134A uses sintetic oil.

[LBPete]

>refrigerant, R12 is hard to contain. It will actually seep through the hose itself

I didnot know this. Learned something new today.often causes a lot of debris to be in the system

I always think the dryer has a filter inside to trap debris. Maybe I am wrong. You don't have to look further than a balloon to understand that a gas can leak past rubber. They go flat in a day or so, faster if filled with helium.

There is always some sort of filter, either in the receiver drier, accumulator or elsewhere in the system. How effective the filter is at catching debris depends on the size and amount of the debris. Also, a common compressor failure is the check valves that among other things, determine the direction of refrigerant flow. When they fail, the compressor can pump debris backwards (out the suction side). If this crap isn't cleaned out, it will get drawn into the replacement compressor without every passing a filter.
Yep, it was common in the R-12 days to add a can (about 1 pound) or 2 every year. Used to, you could buy these little kits of R-12, a can tapper and short hose for a few bucks. R-12 by it self was about $1.50 or less a can. Those back yard recharge kits also introduce air into the system. To do it right, the system must be completely discharged, evacuated with a vacuum pump, and then recharged.
I'm pretty sure I still have one of those kits somewhere in my garage... might even have a can or two of R-12!

Has probably been there 10 years... does R12 have a limited shelf-life?Gold!!! R12 is now considerably more expensive than the $1.50 a can you paid for it way back when. To my knowledge, it doesn’t go bad and currently sells for more than $50 a pound. If you have any car clubs near you, it won’t be hard to find someone to buy those cans from you.
What looks like a filter-dryer is really a suction line accumulator. It holds any liquid refrigerant that comes from the evaporator (inside coil). Since there are more variables with car A/C than residential A/C (especially no filters), the car A/C is more susceptible to slugging (liquid refrigerant hitting the compressor intake). Slugging will kill a compressor.
What determines whether an AC system uses an accumulator or receiver/drier depends on what type of valve or orifice is used to evaporate the refrigerant. Systems that use an expansion valve generally use a receiver/drier. Systems that use a fixed orifice generally use an accumulator. The general purpose of these things is to provide a reservoir for the refrigerant. Like all gasses, refrigerant expands and contracts with temperature and the amount of it circulating depends on compressor speed and A/C load so there needs to be a place for the extra.

[SolderIron]

>If you reuse a known good compressor, replace the clutch and ALL gaskets. replace the gaskets if the system has to be opened for ANY reason.

Are these the o ring gaskets on the lines? Kinda hard to pull all the lines to get to those gaskets.

[rca2000]

One more thing about car A/C. It is HOT under the hood, and this is not too good for compressors, hoses, and such, and all of this extra heat means that more power and refrigerant will be needed ,to produce the cooling effect, than in a home system. I have an old (but great) book called modern refrigeration and air conditioning) from '68, and it explains all of these factors in detail. where as 1 HP of compressor power will produce a ton of refrigeration, or 12,000 btu, in a residential A/C, it takes about 50% more power, to produce the same amount of efrigeration, in a car, and, it takes about 2 tons, or so, to adequately cool a car, due to the enviormental conditions, etc.

(If I am wrong on any of this, Big D, feel free to correct me)

[SolderIron]

>Systems that use an expansion valve generally use a receiver/drier. Systems that use a fixed orifice generally use an accumulator

Both are doing the same function. Is the main differecne on the physical size?

>it doesn’t go bad and currently sells for more than $50 a pound

A neighbor has one of those unopened BBQ size R12 container. He doesn't know he's rich yet.

[skippy_ps]

Sorry about my skinny white boy leg in the pic. :D

[LBPete]

Holy Shit! I'll be your best friend!!! If that box is full of refrigerant cans, you my friend, are rich. My guess is you have a a car that uses R12 and in that case, don't let that box out of sight.

Solderiron, that BBQ size drum holds 30 lbs of refrigerant. He is indeed sitting on a gold mine.

If either of you want to sell some or all of that stuff, I know people that will buy it.

- Pete

[dgwojo]

Luckily I have a supply of R12 for my 1969 Olds Vista Cruiser, $50/pound really sucks. I heard the only reason R12 was phased out was that Dupont's patent ran out on it?? Supposedly R134A is really bad $hit, similar to mustard gas, and it causes testicular cancer, OUCH!!! I also heard that freon goes to the ground and doesn't hurt the ozone for that reason, Al Gore was in on creating the ozone illusion to promote R134A, now my local mechanic is telling me R134A is up for replacement, what gives?? Just my $.02. :no:

[LBPete]

R12 was phased out because it is a restricted greenhouse gas. (Montreal Protocol if I recall) R12 was widely made by companies other than DuPont. I don't know if they licensed the rights to manufacture or the patent expired. What I can say, is only DuPont can legally use the name "Freon" to refer to R12. That is their registered trademark. You just have to look at the picture of the box of R12 elsewhere in this thread to see a different supplier and a different trade name for it. Freon has become the generic name for any kind of refrigerant, kind of like Xerox for photocopiers or Band-Aid for bandages.

R134a (also a Dupont invention, trade name Suva) is also on the way out. Currently demand exceeds production and it is in short supply. There is speculation that the growing Chinese auto industry is soaking up the excess driving prices up and the producers don't want to add production capacity because it will be phased out in a few years. The likely replacement is Carbon Dioxide!

[dgwojo]

The likely replacement is Carbon Dioxide!
CO2 aye, maybe they should just go back to dangerous ammonia like the Servel natural gas refridgerator I got rid of!! That thing was amazing, it ran on a pilot flame, probably for about $.25/month!! Now the Amish are buying them up since they can't buy electricity for religous beliefs/reasons. :yes:

http://www.lehmans.com/shopping/product/detailmain.jsp?itemID=556&itemType=PRODUCT&iMainCat=816&iSubCat=896&iProductID=556

[MCS Guy]

I dont see R134a leaving anytime soon. The refrigerant still works better than CO2 and 134a systems are cheaper right now. While in Europe, its planned for phase out, But the EPA said they probably wont ban R134a in the near future. Its in MOTOR news if you want to read it.

If anything, manufacturers are going to critical charge. A 1/2 oz difference will throw the pressures out of wack. The point in going to the critical charge system is to use less 134a.

As for refrigerant leaks, in any automobile, the engine moves around on its mounts and so forth. So we have to have some sort of flexible hose in order to allow movement. Also, to allow servicing the system, you must have fittings in order to remove failed components. This also give potential leak points. The compressor has a shaft seal to hold refrigerant in and is usually the first thing to go. Blocked condensers or inop cooling fans will kill a compressor quick!

The reason home refrigerators and a/c handlers dont leak much is that there pumps are sealed and all (or Most) joints are sweated copper. Its hard for refrigerant to leak out like that.

Both are doing the same function. Is the main difference on the physical size?

not quite. a receiver dryer (smaller than a accumulator) takes LIQUID refrigerant from the condensor and runs through the water absorbing material. It also filters out debris from the compressor and meters the proper amount of lubricant. Most systems that use a receiver/dryer are systems that use a TXV type system. The TXV regulates liquid refrigerant flow through the evaporator by monitoring the outlet temp of the evaporator. The TXV also must not let liquid refrigerant leave the evaporator.

The accumulator (which is bigger) take the VAPOR and liquid refrigerant from the evaporator. As the systems flows, liquid refrigerant collects at the bottom and gas goes to the top. The gas at the top then flows through a tube internally to the bottom of the accumulator. as the gas flows through this U-shaped tube, it picks up lubrication oil from the bottom via a small hole in the tube. Then the gas/oil mixture leaves the accumulator to the compressor. In this system, an orifice tube is used and the orifice tube is the primary filter. The accumulator is more important than a Receiver/Dryer because it cannot let liquid refrigerant leave it. Otherwise, the compressor goes bye-bye.

During the 70's were TXV systems were the norm, orifice tube systems started comming out. The TXV system has the compressor running at all times and the TXV adjusts to keep cooling at optimum performance. The down side to this system was it was expensive and reduced fuel economy with the compressor being run at all times.

The orifice tube system was cheaper and helped fuel economy, but the compressor cycling control cause a varience in temperature at the duct and in low powered cars, could be felt. This problem was solved in the 80's with varable displacement compressors.

its midnight, and Im done with my tangent.

[LBPete]

That’s good information about the operation of the accumulator. I don’t have much experience with them. TXV (thermal expansion valve) systems definitely cycle. It was necessary to cycle the compressor off to keep the evaporator from freezing. All of the kits I installed had expansion valves and cycling compressors. Later, some of the high end systems used an expansion valve on the evaporator inlet and a POA valve on the evaporator outlet. It regulated evaporator temperature by controlling the pressure inside the evaporator. These systems didn’t cycle and boy did they get cold. They worked real good.

- Pete

[VinylHanger]

I've been blessed with a '91 Chevy PU that the AC still blows ice cold. The compressor has made noise ever since I replaced the motor and we flipped the comp. on it's side. Bad idea. Maybe needs a new clutch? But it is working great. Now if only they made tape decks that kept going and going.

[dewickt]

Just converted my 89 Towncar to 134a, the R12 had leaked down far enough to the point that the compressor would cycle off in a few seconds and air was only cool. Drained system and evacuated it to 29" vacuum for 30 minutes then added 8 oz of new PAG oil, then added 3 pounds for 134a. Head pressure at 2500 RPM is 250 LBS suction is 30 Lbs, nice and cold. Surprised me that I was able to get by with no other changes, system had been rebuilt 8 years ago with new accumulator, O rings, fitting stabilizers, and evaporator, they were still in very good condition, good enough that my leak detector found no leaks.

[skippy_ps]

Terry,

Did you drain the original oil from the compressor or anywhere else? Just curious.

Murray

[dewickt]

No drain of original, the new oil says it will condition and safely mix with old oil. Can says Ester Oil, Automotive Polyol, "best for retrofitting from R12 to R134a"
-Compatible with most materials of construction
-Stable to residual chlorine from R12
-Compatible with Existing Refrigeration Oils
bought it at AutoZone #PY-7, cost $31 to get it all up and cold.

[grumpy]

The shop where i purchased my central air from said we have about 10 years left for R12 and then no more production. Also this is the last year you can buy a 10 sear AC. Next year its up to 11. That equates to roughly 500.00 more for a more efficient compressor.

For cars I have no clue.

[nevermind]

In Europe we can use R409a for replacing all R12 Refrigeration or A/C systems.
You don't have to change anything except the filter dryer.
We use R407a for replacing Freon R 22 and we use R408a for replacing Freon R502.
No one here replaces R12 with R134a.Because R134a uses a totally diferent oil
( Mineral oil doesn't mix with R134a )and because of that ,the A/C system do not respond well and the life of the compressor will be shorter.

[MCS Guy]

No drain of original, the new oil says it will condition and safely mix with old oil. Can says Ester Oil, Automotive Polyol, "best for retrofitting from R12 to R134a"
-Compatible with most materials of construction
-Stable to residual chlorine from R12
-Compatible with Existing Refrigeration Oils
bought it at AutoZone #PY-7, cost $31 to get it all up and cold.

Ester oil is good for doing a minimal retrofit. I have used ester oil on old R12 systems with success.

If your going to replace the compressor, flush out the system and use PAG. If your gonna reuse the compressor as in a minimal retro fit, use the ester oil.