A/C help
Thread Starter
Instructor
Joined: May 2006
Posts: 106
Likes: 0
From: Cary NC
A/C help
i just bought a new compressor and receiver for my 84 corvette and i was wondering how many cans of refrigerant is needed to fill my system and how many things of oil i should buy.
Racer
Joined: May 2004
Posts: 318
Likes: 0
From: Kissimmee FL
Reifil
It depends on the size of the can but in general 2 small cans at the most. Get the r134 with the oil already mixxed in. You can get a gauge at any parts store and you really should use that. Some are inexpensive but will better than not using a gauge, they will say need charging, full, and overfull. Remember to much freon will make you a/c system hot or other problems, this is a case where to much can be a bad idea. Be carefull when using the freon as it will freeze your eyeballs instantly. Where glasses and keep all freon off of you. Good luck....G
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Depends on the gas - the fill is listed on the Blower Motor Housing - most R12 Vettes are 2.25 lbs (3 12 ounce cans) which should be reduced by about 20% if you're switching to R134 - so 2 cans of R134 and a tad of another should be about right. www.ackits.com has a chart where you can get the factory fill specs.
The oil charge is 8 ozs. Add it separately if you want long life. Drain whatever came in the new compressor and dump in 4 ozs. Turn the shaft a dozen or so times in one direction and then in the other. Drain and repeat; then put in 4 ozs. of fresh oil. Put the other 4 ozs in a new accumulator. That will ensure a good supply of oil when you start it up. (Start it up without any oil and your new compressor will immediately seize.) Pull a vacuum and let that vacuum pull in the 1st can (or as much as it will suck out of it). Jump the low pressure switch harness with a paperclip, start the engine and prop the throttle so that it's running at about 1500 rpms, get the main fan running (which on the '84 I believe it does once a/c is commanded) and turn the a/c controls to max. Let the system pull in the balance of the charge monitoring the high side until the pressure is about 2.2 to 2.5 times the temperature of the air across the condensor (so if it's 80 degrees at the condensor, you want to think about stopping once you see 175 to 200 psi on your high side gage. And with a bottom feeder like the Vette, even with main fan running - condensor air temp is usually about 10 degrees hotter than ambient).
When you're done filling it up, plug in the low pressure switch harness and with the a/c still on max, disconnect the blower motor. The low side will drop and the low pressure switch should open cutting power to the compressor clutch. Note that pressure. For R12, it should be 25 psi; for R134 22.5 psi. There is an adjustment screw between the low pressure switch terminals. Turning it clockwise will raise the cutoff threshold; counterclockwise will reduce it. Most need no more than 1/2to a full turn in one direction or the other to get it right, but you may have to unplug the harness, turn the screw a bit and then plug it back in a couple of times to get it right.
The oil charge is 8 ozs. Add it separately if you want long life. Drain whatever came in the new compressor and dump in 4 ozs. Turn the shaft a dozen or so times in one direction and then in the other. Drain and repeat; then put in 4 ozs. of fresh oil. Put the other 4 ozs in a new accumulator. That will ensure a good supply of oil when you start it up. (Start it up without any oil and your new compressor will immediately seize.) Pull a vacuum and let that vacuum pull in the 1st can (or as much as it will suck out of it). Jump the low pressure switch harness with a paperclip, start the engine and prop the throttle so that it's running at about 1500 rpms, get the main fan running (which on the '84 I believe it does once a/c is commanded) and turn the a/c controls to max. Let the system pull in the balance of the charge monitoring the high side until the pressure is about 2.2 to 2.5 times the temperature of the air across the condensor (so if it's 80 degrees at the condensor, you want to think about stopping once you see 175 to 200 psi on your high side gage. And with a bottom feeder like the Vette, even with main fan running - condensor air temp is usually about 10 degrees hotter than ambient).
When you're done filling it up, plug in the low pressure switch harness and with the a/c still on max, disconnect the blower motor. The low side will drop and the low pressure switch should open cutting power to the compressor clutch. Note that pressure. For R12, it should be 25 psi; for R134 22.5 psi. There is an adjustment screw between the low pressure switch terminals. Turning it clockwise will raise the cutoff threshold; counterclockwise will reduce it. Most need no more than 1/2to a full turn in one direction or the other to get it right, but you may have to unplug the harness, turn the screw a bit and then plug it back in a couple of times to get it right.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Originally Posted by kdf1986
Will the R134 recharge cans work on the R12 compressor/cars?
I did not know you could mix the two Freons.
kdf1986
I did not know you could mix the two Freons.
kdf1986
You'll then know all there is to know.
Safety Car
Joined: Jun 2004
Posts: 4,652
Likes: 80
From: Lakeland Florida
Thanks for the tips on the paper. The EPA.GOV paper was pretty good in explaining some of the problems and regulatory issues.
I think that due to the age of my car, 1986, and that I want this done right, and working for the upcoming summer months, I will leave it to a professional shop to make the change.
thanks for the links.
kdf
I think that due to the age of my car, 1986, and that I want this done right, and working for the upcoming summer months, I will leave it to a professional shop to make the change.
thanks for the links.
kdf
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Instructor
Joined: May 2006
Posts: 202
Likes: 16
Originally Posted by SunCr
Depends on the gas - the fill is listed on the Blower Motor Housing - most R12 Vettes are 2.25 lbs (3 12 ounce cans) which should be reduced by about 20% if you're switching to R134 - so 2 cans of R134 and a tad of another should be about right. www.ackits.com has a chart where you can get the factory fill specs.
The oil charge is 8 ozs. Add it separately if you want long life. Drain whatever came in the new compressor and dump in 4 ozs. Turn the shaft a dozen or so times in one direction and then in the other. Drain and repeat; then put in 4 ozs. of fresh oil. Put the other 4 ozs in a new accumulator. That will ensure a good supply of oil when you start it up. (Start it up without any oil and your new compressor will immediately seize.) Pull a vacuum and let that vacuum pull in the 1st can (or as much as it will suck out of it). Jump the low pressure switch harness with a paperclip, start the engine and prop the throttle so that it's running at about 1500 rpms, get the main fan running (which on the '84 I believe it does once a/c is commanded) and turn the a/c controls to max. Let the system pull in the balance of the charge monitoring the high side until the pressure is about 2.2 to 2.5 times the temperature of the air across the condensor (so if it's 80 degrees at the condensor, you want to think about stopping once you see 175 to 200 psi on your high side gage. And with a bottom feeder like the Vette, even with main fan running - condensor air temp is usually about 10 degrees hotter than ambient).
When you're done filling it up, plug in the low pressure switch harness and with the a/c still on max, disconnect the blower motor. The low side will drop and the low pressure switch should open cutting power to the compressor clutch. Note that pressure. For R12, it should be 25 psi; for R134 22.5 psi. There is an adjustment screw between the low pressure switch terminals. Turning it clockwise will raise the cutoff threshold; counterclockwise will reduce it. Most need no more than 1/2to a full turn in one direction or the other to get it right, but you may have to unplug the harness, turn the screw a bit and then plug it back in a couple of times to get it right.
The oil charge is 8 ozs. Add it separately if you want long life. Drain whatever came in the new compressor and dump in 4 ozs. Turn the shaft a dozen or so times in one direction and then in the other. Drain and repeat; then put in 4 ozs. of fresh oil. Put the other 4 ozs in a new accumulator. That will ensure a good supply of oil when you start it up. (Start it up without any oil and your new compressor will immediately seize.) Pull a vacuum and let that vacuum pull in the 1st can (or as much as it will suck out of it). Jump the low pressure switch harness with a paperclip, start the engine and prop the throttle so that it's running at about 1500 rpms, get the main fan running (which on the '84 I believe it does once a/c is commanded) and turn the a/c controls to max. Let the system pull in the balance of the charge monitoring the high side until the pressure is about 2.2 to 2.5 times the temperature of the air across the condensor (so if it's 80 degrees at the condensor, you want to think about stopping once you see 175 to 200 psi on your high side gage. And with a bottom feeder like the Vette, even with main fan running - condensor air temp is usually about 10 degrees hotter than ambient).
When you're done filling it up, plug in the low pressure switch harness and with the a/c still on max, disconnect the blower motor. The low side will drop and the low pressure switch should open cutting power to the compressor clutch. Note that pressure. For R12, it should be 25 psi; for R134 22.5 psi. There is an adjustment screw between the low pressure switch terminals. Turning it clockwise will raise the cutoff threshold; counterclockwise will reduce it. Most need no more than 1/2to a full turn in one direction or the other to get it right, but you may have to unplug the harness, turn the screw a bit and then plug it back in a couple of times to get it right.
Nice post. The only additions I would add are:
When pulling the vacuum, let it continue vacuuming for enough time to boil out any moisture that may have entered the unit. If the hoses were off & open to atmosphere, there will be moisture in it. If the unit was open overnight or longer, I would vacuum (boil) it out for 40 minuites or more.
When recharging you MAY add that first can as a fluid (can upside down) to the Hi side, WITH THE CAR OFF. After adding to the fluid side, the gauges should even out. If the low don't equal the Hi (ENG OFF) there is a blockage. The balance of the charge should be added through the LOW side (can right side up) as described. Make sure to close the red **** on gauge set. NEVER OPEN THE RED **** (on the gauges) WITH THE CAR RUNNING.
