A/C Question

[airboatgreg]

Your system is considered operating normally if on average, your duct temps are between 36-42 degrees F (with R12, and if outside air temps are <100 degrees F) per GM technical information.

I'm not sure about other G-bodies, but a 1987 Olds Cutlass 442 requires 6 ounces (0.17 kg) as is listed as the amount of oil to use in the system. I guess you could use more, but you may be just wasting it. Not sure how much is too much. Remember the oil is miscible with R12 and it gets carried along with the R12. It may just pool there or it may build up somewhere and potentially cause problems. I doubt if you added 6.1 oz. to the system it doesn't hurt it. But the oil isn't what's flashing to cool you down. You put too many oil droplets in the way and you could hinder A/C performance at some point above 6 oz.

You can find this information in at least 2 places. If you still have the original compressor on your car, you can simply look at the label to find out you require 6 oz. of R12 oil, and if you look at the sticker on the evap housing, you'd find 3.25 lbs. as the amount of R12 refrigerant in the system. (B-body uses a bit more, at 3.50 lbs.)

Also, you can find the oil amount per the 1987 Cutlass CSM, R-4 systems distribute that 6 oz of oil as follows:

On page 1B-20-
For full system flush and/or all new system components, you add 3 oz. oil in the compressor, and 3 oz. oil to the accumulator.

On page 1B-18-
New oil must be added to the system when single components are replaced (these are not cumulative, only if the individual component gets replaced)-
- Compressor- drain old compressor oil and measure amount. If < 3 oz. of oil drained, add 3 oz. of new oil. It is stressed in the CSM that a new compressor must have at least 3 oz. of oil when installed.
- Evaporator- 3 oz.
- Condenser- 1 oz.
- Accumulator- drain oil out of old accumulator and measure amount. Add new oil in that amount PLUS 2 oz. If no old oil can be drained, add back 2 oz. of new oil.


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I have never drained any oil out of a R-4 compressor and i replaced thousands. I agree that to much oil is not good but the 6 ounces is for the compressor only. the compressor does not have a sump. The accumulator holds the oil

 

[Turbo Zach]

Another question: Why do some AC systems cycle constantly and others don't? My 1983 Bonnewagon has a 1979 Pontiac 301 but I kept the whole original stock 231 AC system intact. The Turbo 301 used the same mounting brackets for the radial compressor that came on the stock 231 so I sourced those and re-used the stock compressor. I yanked all OBD1 CCC stuff so when I turn the AC on the only control is the low pressure switch. And if there is enough pressure in the system to enable the compressor it will run constantly. Meanwhile on my 2000 Jeep Cherokee w/OBD2 the compressor cycles all the time. Some times less, sometimes more. But it never runs constantly. What are the parameters that govern this? Ambient temperature? Humidity? High/Low pressures? On both vehicles I am getting 35° below ambient so I am not complaining. But the cycling worries me. The FSM says up to 10 cycles per minute is acceptable. Really?

I am no A/C expert and have never been properly trained, but I have worked on a lot of different style systems. Seems like the newer compressors like to cycle on and off. As where the older ones stay engaged. I think it has to do a lot with the high side pressure and condenser cooling. My Monte only uses the low side pressure switch. So if the high side is too high and not cooling fast enough it will cycle the compressor on a newer system. Like idling. I bet if you were going down the highway it would not cycle as much. Plugged condensers or bad condenser fans will do that. I have fixed a lot of machines. I probably don't do everything right, but they work when I am done. Usually a heavy equipment machine A/C only works for a couple years before something always happens. I have found a good reference point is 15psi or 35psi on the low side is a happy medium. One or the other is usually close. High side depends on ambient temperature. 150-250 some where in there. I am always open to learn new tricks, so if I am in left field let me know. I like hearing how other people do things.

 

[69hurstolds]

I have never drained any oil out of a R-4 compressor and i replaced thousands. I agree that to much oil is not good but the 6 ounces is for the compressor only. the compressor does not have a sump. The accumulator holds the oil

Hmmm. You saying GM is wrong? It's right there in the CSM and on the compressor label. I don't doubt you've replaced thousands, but I've followed the CSM adding oil to the system every time I've flushed one and replaced all or nearly everything. No issues so far. But if you've tossed in 10 oz without issue, then the system can obviously hold it. But I've never seen any documentation showing 10 ounces.

Not for nothing, but I would like to see a service bulletin or some other technical write-up saying it's more than 6 ounces before I change my approach. I realize there's all sorts of revisions for service crap, but I've never heard of the 10 ounce rule.

 

[airboatgreg]

Hmmm. You saying GM is wrong? It's right there in the CSM and on the compressor label. I don't doubt you've replaced thousands, but I've followed the CSM adding oil to the system every time I've flushed one and replaced all or nearly everything. No issues so far. But if you've tossed in 10 oz without issue, then the system can obviously hold it. But I've never seen any documentation showing 10 ounces.

Not for nothing, but I would like to see a service bulletin or some other technical write-up saying it's more than 6 ounces before I change my approach. I realize there's all sorts of revisions for service crap, but I've never heard of the 10 ounce rule.

10 ounce for the whole system is a good rule of thumb. The R-4 has no sump so the accumulator is where the oil goes into. You also have the condenser and the evaporator needs which are included in the 10 ounce. The hoses, mufflers and lines also. The desiccant bag also absorbs some and if you use a quality accumulator there are 2 desiccant bags that absorb moisture

 

[g3chevy]

Mac442- THANKS!!! That is what I wanted to see. As for the R-12 equivalent I am using Enviro-Safe R134/R12 replacement. Here is what has changed since I first did this. At the time it was OK to sell R-12 replacement freons. Thus you had a plethora of brands (Freeze12, etc) vying for that market. The stuff Enviro-Safe sold was just another replacement and mixed fine with the original mineral oil in R-12 systems. Next time I ordered I noticed it only said R134a replacement. Huh? Then when I got my 609 certification I saw that R-12 equivalents were banned. But, it was the same stuff, right? Right. Same part number- just different text on can. It is a hydrocarbon based refrigerant and while flammable, works great in either system. But they can't legally SAY it works in R-12 systems. So- I used it and am glad I did. I left the oil alone and only changed the compressor and accumulator. Here is the site https://www.es-refrigerants.com/pro...rial-r134a-replacement-cans-cases/details.asp and here is the R-12 disclaimer https://www.es-refrigerants.com/resources/faq/w/id/76/refid/461/details.asp .

I've been using the Enviro-Safe refrigerant also for over 20 years. Love this stuff. Here is an earlier post discussing this alternative.

R12 Freon

I also recall hearing the same about co2 being considered, but as I recall you’re running pressures in excess of 1000 psi, so it becomes a safety concern, a weight concern to be able to hold those pressures, and a fuel economy concern trying to turn s compressor to make that much pressure...

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