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My son has declared that even with the top off of his 1990 Base Coupe, 90+ degree days are unbearable without his A/C functioning. When we got the car, we had a mechanic throw a charge of coolant in there and he said it worked, but the high-side service port just leaked it all out immediately.
There's a sticker on the fan shroud indicating it was converted to R134a at some point in the past, but there's no information about how much of a charge it was given or how much oil was put in, what kind, etc. I'm going to take a crack at sealing up the system, pulling a vacuum for a while, then charging it up, but I have the following questions:
1. I managed to pull the schrader valve core out of the high-side port, but cannot for the life of me find a matching valve. Anyone know what the size or part number would be? Parts manual from GM indicates it's part of the line. Since the threads on it are all chewed up, I might just purchase a new reproduction line from Zip Corvette anyway.
2. I'm guessing I should change the accumulator/dryer while I'm doing this, but that will remove basically all the oil in the system. Anyone know what the recommended oil for a converted system is? Would it be Ester oil, or would I switch to PAG? Anyting I should/need to do to purge any old oil out of there?
3. Anyone know the system charge amount for R134a? I could look up the original capacity for R12 in the FSM, but I don't know if that'd be the same for R134.
Thanks in advance for any insight you guys could shed (and/or any gotchas to watch out for).
My son has declared that even with the top off of his 1990 Base Coupe, 90+ degree days are unbearable without his A/C functioning. When we got the car, we had a mechanic throw a charge of coolant in there and he said it worked, but the high-side service port just leaked it all out immediately.
There's a sticker on the fan shroud indicating it was converted to R134a at some point in the past, but there's no information about how much of a charge it was given or how much oil was put in, what kind, etc. I'm going to take a crack at sealing up the system, pulling a vacuum for a while, then charging it up, but I have the following questions:
1. I managed to pull the schrader valve core out of the high-side port, but cannot for the life of me find a matching valve. Anyone know what the size or part number would be? Parts manual from GM indicates it's part of the line. Since the threads on it are all chewed up, I might just purchase a new reproduction line from Zip Corvette anyway.
2. I'm guessing I should change the accumulator/dryer while I'm doing this, but that will remove basically all the oil in the system. Anyone know what the recommended oil for a converted system is? Would it be Ester oil, or would I switch to PAG? Anyting I should/need to do to purge any old oil out of there?
3. Anyone know the system charge amount for R134a? I could look up the original capacity for R12 in the FSM, but I don't know if that'd be the same for R134.
Thanks in advance for any insight you guys could shed (and/or any gotchas to watch out for).
Sounds like you know just enough about AC to make wrong decisions. What would lead you to believe that changing the accumulator would "remove basically all the oil in the system"? The majority of the oil is in the compressor. If it has been already converted to 134A then it should have the 134A fittings on it. Not difficult to find. Since you are needing to recharge it, that means the old charge leaked out. Finding that leak would be your first move. What would be the motive in recharging a system that has a leak. Start from scratch. Charge with nitrogen and start bubble testing. Repair the leak, vacuum down and charge with around 80% of what the factory R12 charge is. Gauge up and see what you have. Do you have the nitrogen and/or the flow devices? Do you have a gauge set? Do you know how to purge your equipment? Do you know the proper gauge pressure readings? If the answer is no, Google the phone number of your local automotive AC shop.
Sounds like you know just enough about AC to make wrong decisions. What would lead you to believe that changing the accumulator would "remove basically all the oil in the system"? The majority of the oil is in the compressor. If it has been already converted to 134A then it should have the 134A fittings on it. Not difficult to find. Since you are needing to recharge it, that means the old charge leaked out. Finding that leak would be your first move. What would be the motive in recharging a system that has a leak. Start from scratch. Charge with nitrogen and start bubble testing. Repair the leak, vacuum down and charge with around 80% of what the factory R12 charge is. Gauge up and see what you have. Do you have the nitrogen and/or the flow devices? Do you have a gauge set? Do you know how to purge your equipment? Do you know the proper gauge pressure readings? If the answer is no, Google the phone number of your local automotive AC shop.
Your assessment is not entirely unfair. It's entirely possible I know just enough to be dangerous. The leak was already identified as being the high-side service port Schrader valve so I'm planning to probably replace the whole line. I've previously recharged my truck with a borrowed gauge set and vacuum pump from my local Autozone. I do not have Nitrogen. In the case of the truck I had the pressure chart from the FSM based on temp and relative humidity that I used as a reference. I have the FSM for my son's car as well. And I can certainly bring it back to the mechanic for charging, but since parts aren't readily available no one wants to work on this vehicle for repairs, so I'll need to at least replace the line and any other components before bringing it there, and I'd like to know the best course of action so I know the mechanic is doing the right thing with respect to what oil (if any) is added, etc. I didn't realize the oil primarily hung in the compressor and somehow had it in my mind that a substantial amount would be in the accumulator.
And I appreciate that you're trying to keep me out of trouble with this, but I think lots of folks here take on tasks that have some risk and require climbing a bit of a learning curve if you want to do it yourself correctly. That's what I'm trying to do here. If I assumed I already knew everything, I wouldn't be asking for help.
Your assessment is not entirely unfair. It's entirely possible I know just enough to be dangerous. The leak was already identified as being the high-side service port Schrader valve so I'm planning to probably replace the whole line. I've previously recharged my truck with a borrowed gauge set and vacuum pump from my local Autozone. I do not have Nitrogen. In the case of the truck I had the pressure chart from the FSM based on temp and relative humidity that I used as a reference. I have the FSM for my son's car as well. And I can certainly bring it back to the mechanic for charging, but since parts aren't readily available no one wants to work on this vehicle for repairs, so I'll need to at least replace the line and any other components before bringing it there, and I'd like to know the best course of action so I know the mechanic is doing the right thing with respect to what oil (if any) is added, etc. I didn't realize the oil primarily hung in the compressor and somehow had it in my mind that a substantial amount would be in the accumulator.
And I appreciate that you're trying to keep me out of trouble with this, but I think lots of folks here take on tasks that have some risk and require climbing a bit of a learning curve if you want to do it yourself correctly. That's what I'm trying to do here. If I assumed I already knew everything, I wouldn't be asking for help.
You are entirely correct in saying that every procedure carries risk. Absolutely. However, some carry more of a financial risk than others. That being said, it is not my position to tell anyone what to do with their money. In my opinion, getting advise on an internet forum without other verified confirmations is a crap shoot at best. There will be other comments made here that may differ from mine. Who's is correct? There is one member here who would like everyone to believe he knows everything there is to know about C4's and automotives in general. He has been shown to have given wrong information on more than one occasion. I personally know FA about detailing or buffing paint. I'm not about to come on here and ask how to do it and then heed someone who says "Get a high speed side grinder and outfit it with a 80 grit sanding disk". I might however take some advise on how to change out a fuel filter if I didn't know how. Only you can decide your level of comfort dealing with an expensive component that you are not well versed in.
"The leak was already identified as being the high-side service port Schrader valve so I'm planning to probably replace the whole line."
If you've already found this to be the source of the leak, why not just replace the fill valve instead of the whole line? It's a helluva lot easier and cheaper, it just screws out and you replace it with a new one. I did this and got a new valve from Autozone for $3.89, evacuated and refilled the system, and problem solved. And that was 2 years ago, no leaks since.
"The leak was already identified as being the high-side service port Schrader valve so I'm planning to probably replace the whole line."
If you've already found this to be the source of the leak, why not just replace the fill valve instead of the whole line? It's a helluva lot easier and cheaper, it just screws out and you replace it with a new one. I did this and got a new valve from Autozone for $3.89, evacuated and refilled the system, and problem solved. And that was 2 years ago, no leaks since.
I thought about that. I removed the valve core and tried to match it up unsuccessfullly. Bought various one-off sizes along with some assortments - none match what was in there. In addition, the threads on the valve body itself are all chewed up at the end. Anything trying to O-Ring seal over them (like a gauge set I think) would have a tough time.
Your assessment is not entirely unfair. It's entirely possible I know just enough to be dangerous. The leak was already identified as being the high-side service port Schrader valve so I'm planning to probably replace the whole line. I've previously recharged my truck with a borrowed gauge set and vacuum pump from my local Autozone. I do not have Nitrogen. In the case of the truck I had the pressure chart from the FSM based on temp and relative humidity that I used as a reference. I have the FSM for my son's car as well. And I can certainly bring it back to the mechanic for charging, but since parts aren't readily available no one wants to work on this vehicle for repairs, so I'll need to at least replace the line and any other components before bringing it there, and I'd like to know the best course of action so I know the mechanic is doing the right thing with respect to what oil (if any) is added, etc. I didn't realize the oil primarily hung in the compressor and somehow had it in my mind that a substantial amount would be in the accumulator.
And I appreciate that you're trying to keep me out of trouble with this, but I think lots of folks here take on tasks that have some risk and require climbing a bit of a learning curve if you want to do it yourself correctly. That's what I'm trying to do here. If I assumed I already knew everything, I wouldn't be asking for help.
OK, so I've continued down my path of investigation into the specifics of this A/C system and here's what I've found:
So it looks like there's a total of 8oz. of oil in the system along with 2 1/4 lbs. of R12 originally. Online rule-of-thumb sources seem to suggest that the correct charge of R134a would be (Original Charge in lbs x 0.9) - 1/4 lb. Using that formula here would give (2.25 * 0.9) - 0.25 = ~1.78lbs or 28.4oz. This works out to almost exactly the 80% number that arbee recommended (1.75lbs/2.25lbs), but is pretty far off from the 14.6oz that Dredgeguy recommended. Anyone else have any insight as to which is closer to correct?
Also, there's a table of oil capacities to add depending on what component is replaced:
So it looks like arbee is correct again on this one to a fair extent. I was wrong in thinking "most" of the oil would be lost if the accumulator is changed, but it does look like 3.5oz or about 43% of it will need to be replaced. A few questions on this front as well: The R134a conversion kits on Zip Corvette look like they come with Ester oil. I know the R134a system in my 2002 truck used PAG oil. Is Ester oil the correct choice? Elsewhere in the FSM it calls out "525 viscosity" refrigerant oil. Every reference I can find to this viscosity is for R12 only. Is there a correct and particular viscosity Ester oil that should be used here? And it definitely should be PAG, correct? Finally, there's a note here that says the accumulator should basically ONLY be replaced if it's damaged. I've seen numerous other forums and articles (admittedly not related to the C4 Corvette) that suggest that if a system has been depressurized and/or open to the atmosphere for a long time it's good practice to replace the accumulator. It's only a $20 part, so if there's any value in replacing it while I've got things torn apart, I'm inclined to just do it.
The last important piece of the puzzle I'm working on now is what to expect during/after charging to know whether I've got things working right. Here's the performance table from the original FSM:
My question is: Is there an established way to convert this performance table into what I'd expect with R134a? Do I just use these values as-is (seems unlikely).
Again, thanks in advance for chiming in with some details in an effort to help me maximize my odds of succes (and perhaps minimize the odds that I end up buying a new compressor in a month.
EDIT: One more question: Assuming I pull a vacuum on the system and perform the vacuum hold test, I'm guessing I should need to purge ONLY the charge line from the new can of R134a since the high and low-side lines will still be at nearly full vacuum. Is this assumption correct?
OK, so I've continued down my path of investigation into the specifics of this A/C system and here's what I've found:
So it looks like there's a total of 8oz. of oil in the system along with 2 1/4 lbs. of R12 originally. Online rule-of-thumb sources seem to suggest that the correct charge of R134a would be (Original Charge in lbs x 0.9) - 1/4 lb. Using that formula here would give (2.25 * 0.9) - 0.25 = ~1.78lbs or 28.4oz. This works out to almost exactly the 80% number that arbee recommended (1.75lbs/2.25lbs), but is pretty far off from the 14.6oz that Dredgeguy recommended. Anyone else have any insight as to which is closer to correct?
Also, there's a table of oil capacities to add depending on what component is replaced:
So it looks like arbee is correct again on this one to a fair extent. I was wrong in thinking "most" of the oil would be lost if the accumulator is changed, but it does look like 3.5oz or about 43% of it will need to be replaced. A few questions on this front as well: The R134a conversion kits on Zip Corvette look like they come with Ester oil. I know the R134a system in my 2002 truck used PAG oil. Is Ester oil the correct choice? Elsewhere in the FSM it calls out "525 viscosity" refrigerant oil. Every reference I can find to this viscosity is for R12 only. Is there a correct and particular viscosity Ester oil that should be used here? And it definitely should be PAG, correct? Finally, there's a note here that says the accumulator should basically ONLY be replaced if it's damaged. I've seen numerous other forums and articles (admittedly not related to the C4 Corvette) that suggest that if a system has been depressurized and/or open to the atmosphere for a long time it's good practice to replace the accumulator. It's only a $20 part, so if there's any value in replacing it while I've got things torn apart, I'm inclined to just do it.
The last important piece of the puzzle I'm working on now is what to expect during/after charging to know whether I've got things working right. Here's the performance table from the original FSM:
My question is: Is there an established way to convert this performance table into what I'd expect with R134a? Do I just use these values as-is (seems unlikely).
Again, thanks in advance for chiming in with some details in an effort to help me maximize my odds of succes (and perhaps minimize the odds that I end up buying a new compressor in a month.
EDIT: One more question: Assuming I pull a vacuum on the system and perform the vacuum hold test, I'm guessing I should need to purge ONLY the charge line from the new can of R134a since the high and low-side lines will still be at nearly full vacuum. Is this assumption correct?
I get the feeling you are an engineer or a school teacher. You include details that don't need "detailing" and you are confusing yourself.(see my highlighting above) AC is not rocket surgery. Let me help you out with the oils. The original system used mineral oil. New R134A systems used PAG oil. However, mineral oil and PAG oil do not mix so if you are converting a system, you need to use Ester oil which is compatible with both PAG and mineral oil. Ester oil comes in only one viscosity. As far as the chart goes, once again, there are details which don't need "detailing". Look up an R134A pressure chart on the net and charge it to those specs.(you will see there is a range so if you are attempting to attain the figures in your chart, you are in for a surprise). No harm in changing the accumulator if you wish. Myself, I couldn't care less what the supposed quantity of refrigerant is. I charge to the pressures on the chart. I suggest you do the same and start
OK, so I've continued down my path of investigation into the specifics of this A/C system and here's what I've found:
So it looks like there's a total of 8oz. of oil in the system along with 2 1/4 lbs. of R12 originally. Online rule-of-thumb sources seem to suggest that the correct charge of R134a would be (Original Charge in lbs x 0.9) - 1/4 lb. Using that formula here would give (2.25 * 0.9) - 0.25 = ~1.78lbs or 28.4oz. This works out to almost exactly the 80% number that arbee recommended (1.75lbs/2.25lbs), but is pretty far off from the 14.6oz that Dredgeguy recommended. Anyone else have any insight as to which is closer to correct?
Also, there's a table of oil capacities to add depending on what component is replaced:
So it looks like arbee is correct again on this one to a fair extent. I was wrong in thinking "most" of the oil would be lost if the accumulator is changed, but it does look like 3.5oz or about 43% of it will need to be replaced. A few questions on this front as well: The R134a conversion kits on Zip Corvette look like they come with Ester oil. I know the R134a system in my 2002 truck used PAG oil. Is Ester oil the correct choice? Elsewhere in the FSM it calls out "525 viscosity" refrigerant oil. Every reference I can find to this viscosity is for R12 only. Is there a correct and particular viscosity Ester oil that should be used here? And it definitely should be PAG, correct? Finally, there's a note here that says the accumulator should basically ONLY be replaced if it's damaged. I've seen numerous other forums and articles (admittedly not related to the C4 Corvette) that suggest that if a system has been depressurized and/or open to the atmosphere for a long time it's good practice to replace the accumulator. It's only a $20 part, so if there's any value in replacing it while I've got things torn apart, I'm inclined to just do it.
The last important piece of the puzzle I'm working on now is what to expect during/after charging to know whether I've got things working right. Here's the performance table from the original FSM:
My question is: Is there an established way to convert this performance table into what I'd expect with R134a? Do I just use these values as-is (seems unlikely).
Again, thanks in advance for chiming in with some details in an effort to help me maximize my odds of succes (and perhaps minimize the odds that I end up buying a new compressor in a month.
EDIT: One more question: Assuming I pull a vacuum on the system and perform the vacuum hold test, I'm guessing I should need to purge ONLY the charge line from the new can of R134a since the high and low-side lines will still be at nearly full vacuum. Is this assumption correct?
So I checked with Marc Haibeck to confirm and saw that I had a typo and left out 1 Lb. Marc is the ZR-1 guru and he confirmed as follows:The refrigerant is measured by weight. It should have 1 lb. 14.6 oz of R-134a.
Sorry about the confusion.
I get the feeling you are an engineer or a school teacher. You include details that don't need "detailing" and you are confusing yourself.(see my highlighting above) AC is not rocket surgery. Let me help you out with the oils. The original system used mineral oil. New R134A systems used PAG oil. However, mineral oil and PAG oil do not mix so if you are converting a system, you need to use Ester oil which is compatible with both PAG and mineral oil. Ester oil comes in only one viscosity. As far as the chart goes, once again, there are details which don't need "detailing". Look up an R134A pressure chart on the net and charge it to those specs.(you will see there is a range so if you are attempting to attain the figures in your chart, you are in for a surprise). No harm in changing the accumulator if you wish. Myself, I couldn't care less what the supposed quantity of refrigerant is. I charge to the pressures on the chart. I suggest you do the same and start
Guilty as charged (engineer). I'm an electrical engineer, however, so I tend to try to make sure I understand lots of the details when I'm undertaking something chemical or mechanical (or in this case - both). And thanks for clarifying the oils. I meant to type "definitely shouldn't be PAG..." above, but I especially appreciate you clarifying that there's only one viscosity of Ester oil. I'm going to order some parts and probably undertake this in the next week or two.
Guilty as charged (engineer). I'm an electrical engineer, however, so I tend to try to make sure I understand lots of the details when I'm undertaking something chemical or mechanical (or in this case - both). And thanks for clarifying the oils. I meant to type "definitely shouldn't be PAG..." above, but I especially appreciate you clarifying that there's only one viscosity of Ester oil. I'm going to order some parts and probably undertake this in the next week or two.
Just wanted to double back and post an update in case anyone undertakes this sort of thing in the future. My son and I did this work over the past week and it went... okayish.
We replaced the high-side line, accumulator/dryer, orifice tube, and all the O-Rings at every connection we broke (most of them except the upper evaporator connection and the back of the compressor. Dumped the requisite 3.5oz of Ester oil into the new accumulator before installing it.
Hooked up the gauges and vacuum pump and pulled a vacuum for just over an hour. Then closed off the manifold connections and let it sit for about an hour and a half - no loss of vacuum so I'm thinking we were in good shape.
Purged the charge line and started up the car/compressor and pumped in most of the first can of R134a. Eventually the A/C/ controller tripped out from fast cycling. Rather than jumper the pressure cycling connector, I just had my son disconnect/reconnect the battery. Did this twice. By the time we were loading in the second 12oz can of refrigerant, it had enough low-side pressure to stay on. I didn't do things completely by weight, but we were well into the third can of refrigerant when the pressures got to where I decided we were good to go. Probably around 30oz of R134a total.
Was around 88 degrees with high humidity. Low-side pressure hung steady at about 36 psi.
High side pressure stabilized at around 265psi.
After we were done and shut the car off, static pressure stabilized at a bit above 80psi - suggesting maybe could stand to have a bit more charge. At any rate, the system blew nice cold air and all seemed to be working well during subsequent test drives.
Now to the bad news: I strongly suspect this compressor may not be long for this world. When we were removing the old orifice tube, we found the screen was PACKED with crud:
I've seen folks in other car forums refer to this buildup as "black death" and suggest it was from running the system with moisture in it. I guess we will see what happens over time.
Any chance this level of debris buildup is just typical for a 30 year old system and not an indicator that something's on it's way out?
In any case, after a bunch of hand-wringing and information gathering, we were at least successfully able to get the system back up and running. I'll let folks here know if the crud buildup means the compressor meets an untimely death in the near future.
1990 A/C Resurrection
