Unless you have a vacuum pump and gauges you would be further ahead to take it to an AC shop. If you can get a pump and it holds vacuum 3 cans will do, however you may or may not use all of the 3rd can. See Ogres cave, he has a good article on the AC.
[This message has been edited by tebailey (edited 06-20-2015).]
The system will take approx. 2 1/2 cans of R-134a but it could take a bit more or less. As tebailey has said you MUST evacuate the system to 29" Hg prior to recharging and hold that vacuum for about 30 minute to insure that there are no leaks. You need a manifold gauge set and a vacuum pump to get this done. If all is OK then you start putting refrigerant into the low side fitting on the line start engine and follow the procedure for getting a good charge. I follow the system pressures relative to the ambient temperature and measure the air temps coming from the vents. If you do everything correctly the A/C should blow very cold.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Flotech Afterburner Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
I interpret it that the system was charged but emptied to replace the pressure switch. If that's the case and you don't have a pump and manifold gauges, you can do it with the parts store recharge kits. But the best way is to have a certified automotive AC technician do it.
Using the valve on the front top side of the receiver drier to fill the system, you can unplug the compressor cycle switch harness that plugs into the driver's side top of the receiver dryer. Connect the recharge kit hose and can, insert a jumper wire into the two terminals in the harness and start the engine. Rock the can from upright to horizontal and back while charging. This keeps oil mixed into the flow.
The normal charge for an R12 system is 30-31 ozs 40 oz. I've read on this forum so many times that because of the higher expansion rate of the R134a, that only 80% of the R12 charge should be used. That would convert to 26-27 oz 32 oz. or just a quick shot from a 3rd can. [strike]Two cans should give you cold air. It may not be worth wasting a 3rd just for 1 or 2 ozs.[/strike] My 86 and 87 and my brother's 86 are all working well with just 2 cans, and we're bumping 100 every day, now.
Dennis may be correct on the amount to use, but I erred on the safe side because I didn't want to overcharge the system, and the gauge on the recharge kit indicated it was sufficient.
Edited to correct the capacities needed for recharging.
[This message has been edited by fierofool (edited 06-24-2015).]
Note that using small cans, you loose some refrigerant every time you change cans. 1-2 oz lost is common. Using a full gauge set looses more when you start/finish. Another 1-2 oz. So you never get 3 full cans in the system.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
The system will take approx. 2 1/2 cans of R-134a but it could take a bit more or less. As tebailey has said you MUST evacuate the system to 29" Hg prior to recharging and hold that vacuum for about 30 minute to insure that there are no leaks. You need a manifold gauge set and a vacuum pump to get this done. If all is OK then you start putting refrigerant into the low side fitting on the line start engine and follow the procedure for getting a good charge. I follow the system pressures relative to the ambient temperature and measure the air temps coming from the vents. If you do everything correctly the A/C should blow very cold.
^^ Dennis is correct. About 2 1/2 cans because R134 equivalent is 85-90% of R12 capacity. You should also replace the dryer and orifice filter because of how cheap those items are. You can't refill the system without pulling a vacuum on it or the refrigerant won't suck into a system that's equal atmospheric pressure as the outside. You can "rent" manifold gauge set and vacuum pump at Autozone but it's usually special order. Or buy them at Harbor Freight.
^^ Dennis is correct. About 2 1/2 cans because R134 equivalent is 85-90% of R12 capacity. You should also replace the dryer and orifice filter because of how cheap those items are. You can't refill the system without pulling a vacuum on it or the refrigerant won't suck into a system that's equal atmospheric pressure as the outside. You can "rent" manifold gauge set and vacuum pump at Autozone but it's usually special order. Or buy them at Harbor Freight.
......and if I may again drive the point home that you should not recharge without pulling a vacuum to 29" Hg. Why??? Here is another reason. When the system is discharged outside air enters the system. If the system is open for a few hours, the humidity present can saturate the desiccant in the accumulator, cause icing of the system and at the least lower efficiency as there will be air taking up refrigerant space. That is why sticka01 stated that you should replace the accumulator. Doing the job right the first way will insure that you won't have to do it again a second time. If you cannot afford a vacuum pump, rent one or if you have an large air compressor buy a Roninaire air vac attachment. I use one and on a 5hp unit it works well.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Flotech Afterburner Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
To be honest, the system has not been charged since January, I did an engine swap at the beginning of the year leaving the system was open for about 5 months. We don't get humidity in Colorado, its too dry here. I still need to use a vacuum?
We don't get humidity in Colorado, its too dry here. I still need to use a vacuum?
Does it ever rain there? Do you have outdoor plants that survive without being watered? Have you ever had clouds in the sky? If any answers are 'yes' then you have humidity.
In the case of my 87, it had a charge and was working, though poorly. I inserted a small screwdriver into the schrader valve and slowly released the refrigerant, (helping to promote global warming, so sue me). This should have equalized the system pressure with atmospheric pressure. Without the aid of a vacuum pump, I attached a can of 134a refrigerant and the pressure inside the can overcame the atmospheric pressure in the system and flowed into the system. So, I disagree with the belief that you can't charge the system without pulling a vacuum.
Once the can had equalized pressure with the system, I started the engine and turned the AC on. There was enough pressure in the system that the AC compressor pulled the remainder of the refrigerant into the system. I then added the second can using the car's compressure to pull it in.
At no time was the system ever open to the atmosphere so removing moisture wasn't necessary. But in fieromatty's case, it most definitely needs a vacuum applied, system thoroughly evacuated, flushed and recharged with oil and refrigerant.
Thanks for the heads up. I called my buddy who does HVAC. Said he had a 30 gallon tank of r134a and would pull the moisture out with a vacuum for free. Looks like he is going to fix it for me. Thanks for the information guys.
I inserted a small screwdriver into the schrader valve and slowly released the refrigerant, (helping to promote global warming, so sue me). This should have equalized the system pressure with atmospheric pressure. Without the aid of a vacuum pump, I attached a can of 134a refrigerant and the pressure inside the can overcame the atmospheric pressure in the system and flowed into the system. So, I disagree with the belief that you can't charge the system without pulling a vacuum. .
Only one problem. The system will be at atmospheric pressure by letting all the refrigerant out but all the refrigerant will come out as R-134a is lighter than air and air will get in. . You need to start with a vacuum so the system pulls in a full charge of R-134a. Your method may work but the system efficiency will be compromised.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Flotech Afterburner Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
Dennis, I'm lost on this one. If refrigerant is spewing out of the depressed, not removed, schrader valve, how can air go back in at the same time. The refrigerant is coming out because of it's expansion pressure against the inside of the system, not because it's being replaced by atmosphere. Just like an aerosol can. If I stopped vacating the refrigerant while it's still slightly spewing, indicating it's higher than atmospheric, nothing should enter.
I'm not a physicist, but I don't understand how moisture could enter under those conditions. But, in case I'm wrong, as a matter of yearly maintenance, RockinRoger is coming by one day this week to check the system with the proper equipment.
Dennis, I'm lost on this one. If refrigerant is spewing out of the depressed, not removed, schrader valve, how can air go back in at the same time. The refrigerant is coming out because of it's expansion pressure against the inside of the system, not because it's being replaced by atmosphere. Just like an aerosol can. If I stopped vacating the refrigerant while it's still slightly spewing, indicating it's higher than atmospheric, nothing should enter.
I'm not a physicist, but I don't understand how moisture could enter under those conditions. But, in case I'm wrong, as a matter of yearly maintenance, RockinRoger is coming by one day this week to check the system with the proper equipment.
Even if no air enters the system you need the vacuum to pull a full charge and to confirm that the system has no leaks. . I learned this from the automotive A/C guys who are probably smarter than myself on the subject. My way is to follow accepted practice because it works. You can ignore this, do it your way and what more can I say? The guys on the automotive A/C forum may have a better answer. http://acsource.net/acforum/viewforum.php?f=1
I don't dispute that using a vacuum pump and gauges to evacuate and charge the system are the correct and best way to do it. But if the system has been holding a charge for years without leaking down, the system can be drained of refrigerant without opening it to the atmosphere, and it can be recharged without the use of a vacuum pump. Even if it has been opened for an hour, such as replacing the receiver dryer, it can still be recharged without a vacuum pump. It shouldn't be, but it can be.
Originally posted by fierofool: I don't dispute that using a vacuum pump and gauges to evacuate and charge the system are the correct and best way to do it. But if the system has been holding a charge for years without leaking down, the system can be drained of refrigerant without opening it to the atmosphere, and it can be recharged without the use of a vacuum pump. Even if it has been opened for an hour, such as replacing the receiver dryer, it can still be recharged without a vacuum pump. It shouldn't be, but it can be.
I get what you're saying, however, draining the system to atmospheric pressure through recovery and recharging and OPening the system to atmospheric pressure and then recharging is not the same thing. The first circumstance would be restoring the system to its previous state exactly +/- if it were recharged without vacuum. The latter state would be restoring the system to its previous state with a contaminated charge. The refrigerant temps drop below freezing inside the system. Humid air contamination could result in internal freezing and blockage of the system is my understanding. The vacuuming process not only helps the introduction of the refrigerant, it also lowers the boiling point of any water in the system so that it can boil into vapor and be vacuumed out of the closed system before charging to help prevent the above. That's my understanding.
The ability to hold a vacuum says little about the integrity of your system. If the leak point requires pressure greater than 30 psi to show, you'll pass the vacuum test and fail during the charge when that point is reached, just as I did yesterday.
Go to autozone, rent their pump and gauges if they have them, or pick up a set from Harbor freight and pull it down if you must do it yourself. You'll be much happier, unless there's a leak.
I would also guess that having air in the system would reduce the system performance, even if it doesn't cause icing. The air is displacing refrigerant so there is less refrigerant to transfer heat.
I had my AC compressor replaced and converted to 134a by Robert Finley of Robs Fieros, some 5 or 6 years ago, before he had his accident. It was done with a vacuum pump and manifold gauges. It always cooled, but in the really hot days like we're having now, it was a little less desirable than our other car or truck.
I added refrigerant using the refill kits with the gauge and trigger valve, commonly found at chain stores. It seemed to improve but still wasn't on par with the other cars. That's when I opted to lightly depress the low side schrader valve and release the refrigerant. I then refilled it as described in my earlier post, using 2 12oz cans of R134a.
Roger came by this afternoon and checked the system. It's only a hairline below being at optimum charge. It can't be humidity in the system since it has never been opened to the atmosphere since the initial fill, so I guess it's time to get all that debris that's collected in the AC condenser, along with any chipmunk or rat bedding. A good possibility because the car hasn't been driven much in the past couple of years.
A/C is a closed system. If you need to add refridgerant, you have a leak. In a perfect world, you should never need to add refridgerant, even after 100 years.
A/C is a closed system. If you need to add refridgerant, you have a leak. In a perfect world, you should never need to add refridgerant, even after 100 years.
R134a will leak from the hoses at .04 lbs per foot per year. And this is with hoses that are made for R134a that have the liner in them. R1`34a will leak out of th old R12 hoses at a faster rate as these hoses do not have the liners
Originally posted by fierofool: I had my AC compressor replaced and converted to 134a by Robert Finley of Robs Fieros, some 5 or 6 years ago, before he had his accident. It was done with a vacuum pump and manifold gauges. It always cooled, but in the really hot days like we're having now, it was a little less desirable than our other car or truck.
I'm hoping the parallel flow condenser (which was designed for R134) swap will improve this circumstance tomorrow if the weather permits the necessary hose repair.
Alright so I evaced the system and it held vaccum for 30 min. I started it up, put the ac on low and started to add 134a. The pressure climbed to about 55, but the compressor never kicked on. For some reason the clutch is not engaging. How do I trouble shoot this problem.
I put a new high pressure switch but wasn't sure how to connect the new wire.
This is the one I put in....
It has 2 wires on the connector, the old switch only had 1. I have it disconnected for right now until i know how to hook it up.
Alright so I evaced the system and it held vaccum for 30 min. I started it up, put the ac on low and started to add 134a. The pressure climbed to about 55, but the compressor never kicked on. For some reason the clutch is not engaging. How do I trouble shoot this problem.
I put a new high pressure switch but wasn't sure how to connect the new wire. It has 2 wires on the connector, the old switch only had 1. I have it disconnected for right now until i know how to hook it up.
Where do I start?
I believe you should be running the AC on the HIGH setting while charging...
[This message has been edited by Jason88Notchie (edited 06-24-2015).]
I believe you should be running the AC on the HIGH setting while charging...
I wonder how this really matters. Correct me if I'm wrong but I don't believe the MAX position causes the compressor clutch to lock on. I find that my compressors will cycle, even when on MAX. The fan speed from low to high is just a fan and isn't connected to the compressor. The MAX and NORM selector on the slider only moves the mixer door from a position that allows outside air to be brought in when in the NORM position, to recirculating cabin air in the MAX position. Neither is the mixer door connected to the compressor. Maximum cooling is achieved by re-cooling air that is already cooled.
RockinRoger just put a new compressor on his Formula and ran into the same issue with the switches on the compressor. His solution ended up being to run a wire to a switch in the trunk. He has to get out and manually turn on the switch to engage the clutch and when he stops, he has to get out and turn it off. Though it works, he says that the engine wants to stall at stops because it doesn't bump up the rpm.
In addition to what you're replacing on the system, may I recommend that you also get a new cycle switch set for the 134a refrigerant. Screw it into the receiver dryer and don't fool with adjusting the old R12 by turning it "about an eighth of an in or so".
The old single wire switch grounded through the compressor. Not sure, but can you ground one of those wires and connect the other to the existing wire?
Regarding the compressor cycling, how often should it "click on" whlie idling? I think My Formula which was converted to R134a a few years ago is clicking on far too often. What can cause that?
[This message has been edited by 2.5 (edited 06-24-2015).]
It already had 134a in it before. I don't see how I could have the wrong switch. The high limit switch should only complete the circuit when the compressor is too high right? Everything else is the same.
I will try to run the compressor on High, but I am not sure if that will make much of a difference. All the videos I watched on refilling the system said I need to run it on low.
The compressor cycle switch is the one on the receiver dryer and engages and disengages the clutch. Common habit is is to convert to 134a, leaving the original or replace the receiver dryer and transfer the existing cycle switch to the new receiver dryer. The R12 cycle switch is set for different pressures than are required for R134a due to different expansion rates of the two refrigerants. The switches on the compressor turn the compressor off if the pressures are outside the limits of safe operation so that you don't destroy the system. At least that's the way I understand the operation.
To fix some info on here. R12 charge is 40ozs, R134 should be 32ozs, or 2 2/3rd cans.
I stand corrected. It took a lot of reading, but finally on the last page of the AC section of the 87 Helms manual, page 1B-37, I found that the capacity of the V6 equipped Fiero is 40 oz. of R12. Seems the 4-cylinder cars capacity varied with no specified amount, so you should use a gauge set to recharge those. I'll go back and correct my first posting. Thank you.
And the manual says to place the slider switch on NORM with the fan switch on High. This is to draw air across the condenser, creating a better temperature exchange.
[This message has been edited by fierofool (edited 06-24-2015).]
It already had 134a in it before. I don't see how I could have the wrong switch. The high limit switch should only complete the circuit when the compressor is too high right? Everything else is the same.
I will try to run the compressor on High, but I am not sure if that will make much of a difference. All the videos I watched on refilling the system said I need to run it on low.
I have a 7730 ECM and tried to disconnect the high pressure switch on the compressor and it prevented it from turning on.
I think the switch grounds through the compressor body when the pressure is not excessive. So if you leave it unplugged or have it connected wrong, the compressor will never turn on. Try grounding one wire of the switch.
I wonder how this really matters. Correct me if I'm wrong but I don't believe the MAX position causes the compressor clutch to lock on. I find that my compressors will cycle, even when on MAX. The fan speed from low to high is just a fan and isn't connected to the compressor. The MAX and NORM selector on the slider only moves the mixer door from a position that allows outside air to be brought in when in the NORM position, to recirculating cabin air in the MAX position. Neither is the mixer door connected to the compressor. Maximum cooling is achieved by re-cooling air that is already cooled.
RockinRoger just put a new compressor on his Formula and ran into the same issue with the switches on the compressor. His solution ended up being to run a wire to a switch in the trunk. He has to get out and manually turn on the switch to engage the clutch and when he stops, he has to get out and turn it off. Though it works, he says that the engine wants to stall at stops because it doesn't bump up the rpm.
In addition to what you're replacing on the system, may I recommend that you also get a new cycle switch set for the 134a refrigerant. Screw it into the receiver dryer and don't fool with adjusting the old R12 by turning it "about an eighth of an in or so".
The old single wire switch grounded through the compressor. Not sure, but can you ground one of those wires and connect the other to the existing wire?
Thanks for the clarification. That makes sense. When I filled mine last year the can said the A/C needed to be on the max setting.
I have had good luck with recharging my car by putting the can in a tub of hot water to get it started with a completely discharged system. After a couple of minutes the compressor will kick in. Got this method from old timer at auto parts store. I also have the vacuum pump and have used that. It will take approx. 3 cans.
I have a 7730 ECM and tried to disconnect the high pressure switch on the compressor and it prevented it from turning on.
I think the switch grounds through the compressor body when the pressure is not excessive. So if you leave it unplugged or have it connected wrong, the compressor will never turn on. Try grounding one wire of the switch.
I will try this tonight. I figured the switch only completed the circuit when it when the pressure got too high.Does it matter which one I ground or is it dealers choice?
The old single wire switch grounded through the compressor. Not sure, but can you ground one of those wires and connect the other to the existing wire?
Fierofool and masospaghetti.... you da real mvp.
Grounded one wire and connected the other.... worked like a champ.
