A/C advice - convert to R134 or stay with R12 (Page 2/2)
Sledgehammer MAY 31, 12:02 AM
Thanks for all the help
gjgpff JUL 19, 07:09 PM
Sledgehammer's question seemes similar to mine, so I'm going to post here. When I bought my 1988 4cyl Fiero the previous owner, who'd had it for about 18 months, said that the A/C didn't work. He gave no specifics beyond that. Here's what I've learned:
1) When turned on, the system does not cool the interior of the car. So, it wasn't like the previous owner didn't know where the A/C on/off switch was or anything. I was kind of hoping for that, but I guess I was a little optimistic.
2) The compressor appears to kick in and its clutch appears to function. When I turn on/off the A/C I can hear the clutch kick in. Also, my rev's change indicating that the clutch is putting a load on the system.
3) The system appears to pressurize at least a little. It was probably wrong, but I let a little air/gas out through the schrader valve at the top of the accumulator and I got an encouraging hiss.

Here's what I don't know:
1) Is this system set up for R12? How can I be sure? The accumulator has, what I've been led to believe are R12 type fittings (Shrader valves) and there's a sticker with "R-12" on it:



2) If the system is set up for R-12, what else do I need to know in order to make a decision regarding topping off with R12 or going to R134a? After 32 years is it possible that the system will still work with just a charge of R-12? I know for a fact that the car spent many years in Arizona, so it is very likely it's A/C got a regular workout.

Thanks again!

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Geoff Gibbons
1988 4cyl Manual

Dennis LaGrua JUL 19, 07:18 PM

quote
Originally posted by RWDPLZ:


There he is! What took so long?



The information that I provide was given to me by a tech in a local Automotive A/C shop who I learned from. I always go with what the pros tell me. Its always worked on the systems that I converted over to R-134a , so disagree if you like. The knowledge and value has been proven on this end.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
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" ON THE LOOSE WITHOUT THE JUICE "

Raydar JUL 19, 08:00 PM

quote
Originally posted by RWDPLZ:
There he is! What took so long?



What he said is true. If the system has "R12" oil in it, use Ester oil.
If it's been completely rebuilt and flushed, use PAG.

With that said... it's been my experience that compressor manufacturers/remanufacturers will not warranty a compressor unless you have proof-of-purchase for a new accumulator/dryer, and possibly orifice tube, too.
At that point, almost all of the old oil is gone, anyway. Not much more trouble to just flush the entire system and refill it with PAG.
RWDPLZ JUL 20, 09:37 AM

quote
Originally posted by gjgpff:

1) Is this system set up for R12? How can I be sure? The accumulator has, what I've been led to believe are R12 type fittings (Shrader valves) and there's a sticker with "R-12" on it:



2) If the system is set up for R-12, what else do I need to know in order to make a decision regarding topping off with R12 or going to R134a? After 32 years is it possible that the system will still work with just a charge of R-12? I know for a fact that the car spent many years in Arizona, so it is very likely it's A/C got a regular workout.

Thanks again!




1. Yes, that system is still set up for R-12, the ports don't have the conversion fittings and no sign of a conversion sticker.
2. You need to determine if the system has any charge. You can press a screwdriver tip on one of the schrader valves briefly and see if anything comes out, if there is pressure, you'll need a gauge set to determine the state of charge.
Will JUL 20, 11:26 AM
There are a number of R12 drop-in replacements on the market. I've used products from these guys with good success: https://www.es-refrigerants.com/?site=dom

Typically, an R12 system converted to R134 will not perform as well as it did originally. There are things you can do to help, like use a variable orifice valve instead of the factory fixed orifice valve, but those don't change the fact that the condenser designed for R12 is not as good with R134 as it is with R12, and conversely, does not perform as well with R134 as a condenser designed for R134 would. I have not heard of a drop-in R134 style condenser for the Fiero.

Also, R134 is more sensitive to charge weight than R12. An R12 system can be charged fairly correctly by watching the high side/low side pressures, while an R134 system is difficult to charge correctly by watching pressures. To really charge an R134 system correctly, you need to vacuum the system down and then blow in the correct weight of refrigerant... this is much more difficult to DIY.

Also, the reason an R12 system needs to be vacuumed extensively is that R12 reacts with moisture to form corrosive compounds. The R12 replacement refrigerants do not, making it easier to vacuum the system out as the requirements are less stringent.

All that being said, don't bother converting to R134... it's more trouble than it's worth and you'll get a system that doesn't work as well as original.

You *WILL* need a new compressor and dryer and the right oil for your refrigerant choice.

I can't recommend a variable orifice valve enough... it really broadens the window of RPM and vehicle speed at which you get max A/C effectiveness.

[This message has been edited by Will (edited 07-20-2020).]

gjgpff JUL 21, 03:09 PM

quote
Originally posted by Will:

There are a number of R12 drop-in replacements on the market. I've used products from these guys with good success: https://www.es-refrigerants.com/?site=dom

...

You *WILL* need a new compressor and dryer and the right oil for your refrigerant choice.

I can't recommend a variable orifice valve enough... it really broadens the window of RPM and vehicle speed at which you get max A/C effectiveness.




Thanks for the detailed response, I'm thinking you're referring to the "Artic Air for R12 Systems" product in the above link? Looks reasonable.

I get that I will need a new dryer, but why will I need a new compressor? Is it just very very likely given the age of the vehicle, how long it has been since the AC worked, etc?

The refrigerant oil for the compressor would be ester oil since it's R-12 (like?), right?

For sure I'll be getting a variable orifice valve.

[This message has been edited by gjgpff (edited 07-21-2020).]

gjgpff JUL 21, 03:51 PM

quote
Originally posted by RWDPLZ:


1. Yes, that system is still set up for R-12, the ports don't have the conversion fittings and no sign of a conversion sticker.
2. You need to determine if the system has any charge. You can press a screwdriver tip on one of the schrader valves briefly and see if anything comes out, if there is pressure, you'll need a gauge set to determine the state of charge.



So, the schrader valve already gives a hiss when pressed, therefore I'll be using a gauge to determine how much charge is in there and/or removing any R-12 that is present, right?


I'm kind of convinced by Will's reasoning to go the R-12 route instead of R-134a, but there's still alot of figuring out to do.
RWDPLZ JUL 21, 04:46 PM
R-12 replacements are typically propane or other flammable gas based, and a bad idea. People typically go this route because they want a cheap, easy fix. They are not NHTSA approved and can be very dangerous.

R-12 oil is 525 viscosity mineral oil, not ester oil. Total Fiero capacity is 8 oz

If pressing the schrader valve gave a weak hiss, it's likely empty, if it was a strong loud hiss it might be partially charged, a gauge set is the only way to tell.

It is possible to get an R-12 system functional again, but the gas is prohibitively expensive. Fiero capacity is 2.5lbs, and you need EPA section 609 certification to purchase it (you can take and pass the test online, really easy). Few shops will service an R-12 system anymore unless you live in a highly populated desert region (and no shop will touch an alternative refrigerant system). The reason is shops are required to have separate systems for different refrigerant types. A dedicated A/C shop may be able to afford this, but most smaller shops won't put up with the expense.

You need a new accumulator (dryer) to replace the desiccant that is likely saturated with moisture at this point. A new compressor is a good idea as the originals are all 30+ years old at this point, and tend to be the primary source of leaks, at the shaft seal or body o-rings.

An R-134A conversion that is done PROPERLY will cool 90%+ as well as an R-12 charged system. Charging by weight not pressure is key. 3 12oz cans is close enough.

Ester oil was introduced and sold by the automotive aftermarket (adapted from residential/commercial refrigeration systems) specifically for use in conversions when it was widely believed that mixing mineral and PAG oils resulted in a corrosive substance. However, it is not supported by any of the OEM's or reputable aftermarket compressor manufacturers. According to AC Delco 'Guidelines for Retrofitting Vehicles to R-134a' Page 16:


quote

5. PAG or V5 Oil Compatibility
Contrary to information published to date outside of ACDelco, mineral oil and PAG or V5 oil are chemically compatible. The mineral oil left in the system after reclaiming the R-12 can remain in the system with no harmful effects. However, the mineral oil will not mix with the R-134a, and so will not circulate and perform its lubricating function. Testing has shown that most of the mineral oil will eventually collect in the accumulator. The system will operate properly as long as refrigerant charge amounts are strictly adhered to.

6. Retrofit Charge Level
The retrofit R-134a charge level is more critical than with R-12 systems. Overcharging may push the mineral oil out of the A/D and cause it to circulate as a liquid. This is more likely to result in compressor damage. Undercharging may lead to loss of performance



This is why you want to remove as much of the old mineral oil as possible. Replacing the accumulator and compressor will eliminate most of it, and flushing the lines and evaporator will replace the majority of the rest. Many people have used ester and it worked, but it will void any warranty for a compressor. Ester is also only available in 100 viscosity, where PAG is available in many ranging from 46 to 150, the correct viscosity dictated by compressor design.
gjgpff JUL 22, 12:13 PM

quote
Originally posted by RWDPLZ:

R-12 replacements are typically propane or other flammable gas based, and a bad idea. People typically go this route because they want a cheap, easy fix. They are not NHTSA approved and can be very dangerous.

R-12 oil is 525 viscosity mineral oil, not ester oil. Total Fiero capacity is 8 oz

If pressing the schrader valve gave a weak hiss, it's likely empty, if it was a strong loud hiss it might be partially charged, a gauge set is the only way to tell.

It is possible to get an R-12 system functional again, but the gas is prohibitively expensive. Fiero capacity is 2.5lbs, and you need EPA section 609 certification to purchase it (you can take and pass the test online, really easy). Few shops will service an R-12 system anymore unless you live in a highly populated desert region (and no shop will touch an alternative refrigerant system). The reason is shops are required to have separate systems for different refrigerant types. A dedicated A/C shop may be able to afford this, but most smaller shops won't put up with the expense.

You need a new accumulator (dryer) to replace the desiccant that is likely saturated with moisture at this point. A new compressor is a good idea as the originals are all 30+ years old at this point, and tend to be the primary source of leaks, at the shaft seal or body o-rings.

An R-134A conversion that is done PROPERLY will cool 90%+ as well as an R-12 charged system. Charging by weight not pressure is key. 3 12oz cans is close enough.

Ester oil was introduced and sold by the automotive aftermarket (adapted from residential/commercial refrigeration systems) specifically for use in conversions when it was widely believed that mixing mineral and PAG oils resulted in a corrosive substance. However, it is not supported by any of the OEM's or reputable aftermarket compressor manufacturers. According to AC Delco 'Guidelines for Retrofitting Vehicles to R-134a' Page 16:


This is why you want to remove as much of the old mineral oil as possible. Replacing the accumulator and compressor will eliminate most of it, and flushing the lines and evaporator will replace the majority of the rest. Many people have used ester and it worked, but it will void any warranty for a compressor. Ester is also only available in 100 viscosity, where PAG is available in many ranging from 46 to 150, the correct viscosity dictated by compressor design.



So, this comment and comparing prices for R-12 vs R-134a has kind of convinced me to retrofit. I've also done some looking around to see what's involved in a compressor retrofit and it looks do-able, assuming I can find a way to acquire/borrow some of the specialized tools.

So, my plan right now is the following:
1) Pump out any remaining R-12 in the system.
2) Get a "no A/C" belt, and remove the compressor, and the hoses to it, plugging them and storing them somewhere clean and dry. Also, plug the system so it stays as clean as it is prior to flushing it.
3) Refurbish the compressor as time permits. I'll try to follow this youtube video: "Delphi Harrison V5 A/C Compressor - Full Teardown and Reseal"
4) When the compressor is ready.. or the refurbish failed and I get a new compressor, install, flush everything, vacuum test, replace other gaskets, etc.
5) Charge with R134a.
6) Chill

Does anyone have tips/advice regarding getting the loan of specialized pullers, tools, etc?

[This message has been edited by gjgpff (edited 07-22-2020).]