Hello All!

I'm looking to work on my A/C and I need some advice.

I have two questions:

1) Is it safe to assume my system has lost enough R-12 over the last 20 years (since it's no longer cold when I turn it on) that I need it refilled (and thus need to covert to R-134a), or is there some other troubleshooting list I can work from? The system used to be cold but has progressively lost its potency over the years. My car is an 86 GT with no mods.

2) If I do need a conversion, what's involved? I've searched the net and found Ogre's rundown on the conversion but it's not "dumbed down" enough for me to understand. From what I gather from that document and reading the forums, it sounds like I have to:

a) replace the ACC/dryer and orifice tube
b) replace all the o-rings and Schrader valves
c) vacuum test the system for leaks
d) add appropriate oil and charge system with R-134a

Please feel free to confirm my understanding, or set me straight.

Thanks in advance for everyone's collective wisdom!

------------------
Wesley A. Williams
MAFOA

I have yet to see an a/c system that has kept the original charge forever, so yes, it is safe to assume the system is *at least* low. The most reliable way to check is a set of a/c manifold gauges. Most people won't go through the trouble of buying a set (they are not expensive at Harbor Freight) and buying a book to learn how an a/c system works. Mine has paid for itself many times over.

If the system is just low you could simply have an a/c shop recharge it with R-12. It is expensive but very simple to top it off. Don't do anything like flush the system, just a simple top off. Leave all the old seals in place and untouched. As soon as you loosen a connection with the old seals, they will never hold a seal again.

If you want to work on your own car then go with the R-134a (or alternatives like ES-12a) conversion kit. Personally I would not replace the accumulator or fixed orifice tube as that requires opening the system (and replacing the seals). Of course an a/c shop can do the work but it is gonna cost ya.

My steps for conversion:

Place new R-134a conversion fittings over old R-12 fittings, both high and low side.
With the system empty, pull a vacuum on the low side using an air compressor and vacuum pump ($15 Harbor Freight).
Check for leaks, repair as needed, pull vacuum again. (The hotter the temp outside the better)
After about 60 minutes at 28" of vacuum remove vacuum pump. Start car, a/c on normal (not max), fan on high.
Using the manifold gauge set, add new R-134a with suggested amount of oil. You can add it with the can upside down as the accumulator is downstream of the low port. When there is sufficient pressure the compressor will kick on.
Keep adding R-134a until the low side reaches about ~32psi. Use a meat thermometer stuck in the middle vent to watch the air temp. It will get colder as you get to your optimum amount of R-134a in the system. If you overfill, it will start getting warm again.

Good luck. A/C can be a pita.

I just fixed mine up.

Everything you listed I also did but found two more problems.

The lines from the pump to the firewall had been flexed so many times over the last twenty years that they had a leak. You can buy a $12.00 UV light to check for leaks (good investment) look where the lines meet the metal connectors. I also put in both Prothane bushings on the dogbone to prevent this. I had only installed one (of the two bushings) before to keep the vibration down. But if I was going to invest this much in the air conditioing I wanted the hose to last.

Also after filling with R134A for a couple of days I found the compressor was also leaking. Again the seals are twenty years old. Replaced the pump, new pump DOES NOT come with the high and low pressure sensors even though the auto parts store will tell you they do. It is impossible to get the old sensors out of the pump after twenty years.

Now I have cold air (finally).

quote Originally posted by Hudini: I have yet to see an a/c system that has kept the original charge forever, so yes, it is safe to assume the system is *at least* low. The most reliable way to check is a set of a/c manifold gauges. Most people won't go through the trouble of buying a set (they are not expensive at Harbor Freight) and buying a book to learn how an a/c system works. Mine has paid for itself many times over. If the system is just low you could simply have an a/c shop recharge it with R-12. It is expensive but very simple to top it off. Don't do anything like flush the system, just a simple top off. Leave all the old seals in place and untouched. As soon as you loosen a connection with the old seals, they will never hold a seal again. If you want to work on your own car then go with the R-134a (or alternatives like ES-12a) conversion kit. Personally I would not replace the accumulator or fixed orifice tube as that requires opening the system (and replacing the seals). Of course an a/c shop can do the work but it is gonna cost ya. My steps for conversion: Place new R-134a conversion fittings over old R-12 fittings, both high and low side. With the system empty, pull a vacuum on the low side using an air compressor and vacuum pump ($15 Harbor Freight). Check for leaks, repair as needed, pull vacuum again. (The hotter the temp outside the better) After about 60 minutes at 28" of vacuum remove vacuum pump. Start car, a/c on normal (not max), fan on high. Using the manifold gauge set, add new R-134a with suggested amount of oil. You can add it with the can upside down as the accumulator is downstream of the low port. When there is sufficient pressure the compressor will kick on. Keep adding R-134a until the low side reaches about ~32psi. Use a meat thermometer stuck in the middle vent to watch the air temp. It will get colder as you get to your optimum amount of R-134a in the system. If you overfill, it will start getting warm again. Good luck. A/C can be a pita.

I did the 'unopened change over' on my daily driver about a month ago, worked fine at first but now im having troubles this last week. When the compressor kicks on the belt squeals like hell for a moment. ( and ya, its tight ). Im guessing its time for a new compressor ( and o-rings and dryer while i have it apart ) . Cheapest ive found is 199 at the local autozone ( blah )

Im guessing the extra pressure + oil mixing might have been too much for it. Last year i had a friend with R12 and it worked fine, for about 4 months when it slowly leaked out. ( and i unplug it over the winter, so i can use the AC button to kick the fan on manually ).

Sooo its not foolproof :|

If your Fiero's air conditioning has worked well for years but is now in need of a recharge - I believe your very best option is to top off the charge with R12. Yes, R12 is more expensive, but it's what your Fiero's AC system was designed to use. No changes needed; fill and go.

If you just must convert to R134 then there's a few things to be aware of. First (and most important) is that most Fiero V6 AC compressors are not capable of working with the higher pressures of a R134 charge. They'll work for a short time and then fail; usually, it'll just lock up. Make sure you've got the late design compressor - or you'll need to replace it as part of the changeover. Don't try to make the wrong compressor work; it'll die, and when it does it'll spread debris throughout the system, causing more problems and expense.

The accumulator MUST be replaced as part of the changeover. Do NOT attempt to run R134 with the Fiero's original accumulator - it'll break down internally and spread debris throughout the system. This will cause the compressor to fail and leave you with a huge mess to clean up. Don't do it; replace the accumulator.

You'll want to change the orifice tube, too. This will greatly improve the cooling performance of your system with R134 in it. It'll never be as good as it was with R12, but you can get it good enough.

You need to replace the oil with 134 compatible oil - and it's a good idea to replace all the O-rings in the system with R134 compatible parts.

Some will argue that you can do much less and still have it work with R134. Yes, but - how long will it last? It's very easy to convert a system and have it last 6 months - but it's a lot more difficult to do it and have it last the life of the car.

Three questions to add:

1. I read somewhere (a car mag I believe) that there is actually a special hose material for 134a..is this true?

2. Is a variable orifice better than a fixed orifice....I see both advertised.

3 .What years should a donor for a "new" style compressor be looked at?

quote Originally posted by rjblaze: Three questions to add: 1. I read somewhere (a car mag I believe) that there is actually a special hose material for 134a..is this true? 2. Is a variable orifice better than a fixed orifice....I see both advertised. 3 .What years should a donor for a "new" style compressor be looked at?

Yes, there is a special (improved) hose material for 134. It's not necessary in a Fiero; as long as the hoses stay "damp" on the inside with the circulating oil they'll hold 134 in just fine. There's more leakage through the O-rings at the joints, anyway.

A variable orifice will give you much better cooling at low speeds / idle. If you have the option, the variable orifice is the one to choose.

Fiero V6 compressors changed over in late '87. I've never researched what other vehicles use the same compressor - but I'm sure there's quite a few. If you buy a replacement compressor, avoid rebuilt units. I don't know what the problem is, but rebuilt compressors have a high failure rate. Install a new compressor if you can, it'll last a lot longer.

quote Originally posted by User00013170: I did the 'unopened change over' on my daily driver about a month ago, worked fine at first but now im having troubles this last week. When the compressor kicks on the belt squeals like hell for a moment. ( and ya, its tight ). Im guessing its time for a new compressor ( and o-rings and dryer while i have it apart ) . Cheapest ive found is 199 at the local autozone ( blah ) Im guessing the extra pressure + oil mixing might have been too much for it. Last year i had a friend with R12 and it worked fine, for about 4 months when it slowly leaked out. ( and i unplug it over the winter, so i can use the AC button to kick the fan on manually ). Sooo its not foolproof :|

Try a bit more oil. When I changed over my '85 S10 with the 2.8L it started making these awful noises from the compressor. I added more oil until it quit making noise. Been fine now for many years. No problems with the accumulator either.

[This message has been edited by Hudini (edited 06-06-2007).]

Whuffo has things pretty well covered with correct information. Read his advice carefully, but I still have to add my own two cents worth:

As far as I know, all 4-cylinder Fieros used the GM/Harrison V5 compressor, which is a pretty sound unit. The early V6 Fieros used the fragile GM/Harrison DA6 compressor, while the later V6es used the much more robust HR6 ("Harrison Redesigned") compressor. Different versions of the V5 and HR6 compressors have been widely used in GM cars from the mid '80s clear up to the present. It is important to note that if you are replacing a DA6 compressor, you can and probably should replace it with the later and much more reliable HR6; the price will be about the same. If you still want to stick with the OEM DA6 compressor, buy a new one rather than a rebuild; the DA6 has aluminum cylinders, and they are notoriously difficult to rebuild correctly.

The current recommendations from GM and the EPA for retrofitting a Fiero to R134A are 1) properly recover all R12 refrigerant remaining in the system, 2) don't flush the system or worry about removing the old mineral-based refrigerant oil, 3) replace the accumulator and orifice tube, 4) replace or convert the old R12 service fittings to R134A fittings, 5) add 8 ounces of PAG or Ester refrigerant oil (Ester oil is somewhat more compatible with the old mineral oil still in the system), and 6) evacuate and recharge the system with ~36 ounces of R134A. You can optionally replace the R12 pressure cycling switch with one optimized for R134A (~8 psi lower switching pressures), adjust your existing switch to lower the switching pressures (yes, it's possible!), or just leave it alone.

Concerning the orifice tube. A new original-size (white) orifice tube will work just fine with R134A, and it will only cost about $2. A variable orifice tube may work slightly better, especially at idle, but it will cost you more than $20 to find out. My personal opinion is that it won't make much difference which you use, given the small cabin of the Fiero, its location in front of the hot engine compartment, and the fact that the same V5 or HR6 compressor is used on many GM cars with much larger cabins.

My '88 Fiero actually came from the factory with barrier style hoses, which are recommended for use with R134A. But as Whuffo correctly stated, older hoses that have had mineral-based refrigerant oil running through them will work just fine with R134A. The official position of GM and the EPA concerning retrofits from R12 to R134A is that you do not need to replace the older, non-barrier style hoses.

NB -- Legally-recycled R12 has become so valuable today that many A/C shops will recover the residual R12 from your system at no charge! They can sell your old R12 to a recycler, so they still make money on the deal. It's a rare win/win situation for all of us.

[This message has been edited by Marvin McInnis (edited 06-06-2007).]

Don't flush the A/C system? That goes against everything IMACA taught me. The only time I have seen GM state not to flush A/C systems is when they employ a crossflow condensor which cannot be flushed of all particulate matter, so in the case of catastrophic compressor failure, the condensor must be replaced as well otherwise when those debris finally loosen and make their way back through the lines, the new compressor is now destroyed as well.

R134a is a MACS approved flushing agent for refridgerant and oils, but not particulate matter, which is where you have the actual chemical flushes found at parts stores.

I have read where the EPA has stated that following a study, R-12 mineral oil has no effect on seals overtime and has no effect on R134a either, therefore it can be left in the system. However, my personal belief, you are still displacing 6 to 8 ounces of ester oil and R134a due to leaving the mineral oil in it.

quote Originally posted by Marvin McInnis: If you didn't replace the accumulator, it is likely that the dessicant bag has ruptured

I have converted 3 cars to R-134a (1 to ES-12a) and never had any problems like this so I have to ask what causes the desiccant to rupture?

quote Originally posted by Hudini: ... what causes the desiccant to rupture?

To quote from the Ford document you cited, "The refrigerant system should ... be flushed for ... Catastrophic accumulator failure involving a ruptured desiccant bag."

But you ask a good question. My guess would be deterioration due to age (20+ years on our Fieros), plus additional stresses due to the change of refrigerants, and the fact that the XH-5 desiccant used in our factory-installed accumulators is incompatible with R134A. (Replacement accumulators use XH-7 or XH-9 desiccant, both of which are compatible with both R12 and R134A.) There is also the issue of up to 4 ounces of mineral-based refrigerant oil that will still be sitting in the bottom of the old accumulator. Since it is insoluble in R134a, the old mineral oil will collect as a sludgy, inert mass in the bottom of the accumulator, and enough of it it may restrict refrigerant access to the filter and/or desiccant bag, and it may also obstruct the oil bleed hole.

quote I found an interesting article from Ford: ... The only time that an accumulator or orifice tube should be replaced is if there is a catastrophic failure of the compressor or if a non-repairable accumulator failure is leaking refrigerant.

Apples and oranges. Ford's statement is clearly in the context of an existing R134A system, but we are discussing retrofits from R12 to R134A here. All authoritative sources I've seen call for replacement of the accumulator when converting a system from R12 to R134A, and recommend cleaning or replacing the orifice tube. A new orifice tube for GM cars is only $2, so why not just replace it? (The Ford products I've seen use an orifice tube that is permanently embedded in a tube/hose assembly, so the cost of replacing it would probably be much higher.)

quote ... Tests have shown that A/C performance does not degrade until more than 90% of the [orifice tube] screen area is totally blocked.

I'm confident that's true. But again, an orifice tube for a GM car only costs $2 and a full set of O-rings is only about $5, so why not just replace it? Examining the screen on the old orifice tube will also give you a good idea of your compressor's health. (1 or 2 small flakes of metal are usually OK. Lots of metal or other debris => bad news.)

quote I have converted 3 cars to R-134a (1 to ES-12a) and never had any problems ....

I have to state for the record that ES-12 refrigerant is not an approved refrigerant under the EPA's SNAP program, and is thus illegal to use in a motor vehicle A/C system. Per the manufacturer, ES-12 is composed of alkanes (i.e. propane, butane, pentane, etc.) and is compatible with mineral oil. It may actually be a pretty good refrigerant, but it costs about the same as R134A and it's still illegal. You may choose to use ES-12 in your car anyway, and you may be OK as long as you are the only person who ever works on it, but anyone considering doing this should carefully consider what they're getting themselves into.

[This message has been edited by Marvin McInnis (edited 06-06-2007).]

quote Originally posted by Marvin McInnis: I'm confident that's true. But again, an orifice tube for a GM car only costs $2 and a full set of O-rings is only about $5, so why not just replace it? Examining the screen on the old orifice tube will also give you a good idea of your compressor's health. (1 or 2 small flakes of metal are usually OK. Lots of metal or other debris => bad news.)

Hey Marvin, where can I get the o-rings for an 88 V6 Fiero? Thanks, and sorry for the hijacking.

Good information to know. Thanks for posting it.

quote Originally posted by TG oreiF 8891: ... where can I get the o-rings for an 88 V6 Fiero?

Any decent auto parts store should have generic O-ring sets for GM A/C systems in stock. I bought a set for my '88 V6 Fiero about two months ago from a local Advance Auto Parts/Parts America store.

FYI: Black O-rings are usually only compatible with R12 and mineral oil. Green or blue O-rings are intended for use with R134A systems, but they are also backwards compatible with R12. The price is about the same, so I go for the green or blue.

[This message has been edited by Marvin McInnis (edited 06-06-2007).]

You can go here and get your Accumalater/Dryer and save some bucks
www.acsource.net/xcart/home.php
I have also purchased from:
http://stores.ebay.com/Texaserick-2006
I purchased on Sunday, and my items were here on Tuesday. In all fairness we both were in the Texas though. One can save some good bucks from both of these.Texaseric also has a website WWW.Texaserick.com. Acsource has all of the O-rings and schrader valves its for the conversion. I have also purchased conversion kits at NAPA that were fair priced and had all that I needed to do the switch over to 134a. Good Luck on your efforts

Joe

Thanks everyone for sharing your experiences. I'll post up and let you know how I make out!

------------------
Wesley A. Williams
MAFOA