AC problems, new parts no cool!
Thread Starter
6th Gear
Joined: Feb 2013
Posts: 6
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AC problems, new parts no cool!
1981 Chevy Corvette 32 k mile all original, except for the AC.
Just converted everything to R134, new Compressor, Condenser & Dryer. Compressor head pressure is running around 270 to 300, should be around 240. Mechanic said the stock condenser for the old R12 systems are not big enough to handle the heat generated by R134. So the car does not cool well at all especially in hotter temps over 90 degrees
Has anyone heard of this a do you recommend going to a larger condenser? They told us to put a push fan on it. There is only ½” between the Hood & Condenser with the hood open so there is not much room for a fan. So I don’t think a fan will fit. Do you know of a heavy duty Condenser that would work on this car?
Just converted everything to R134, new Compressor, Condenser & Dryer. Compressor head pressure is running around 270 to 300, should be around 240. Mechanic said the stock condenser for the old R12 systems are not big enough to handle the heat generated by R134. So the car does not cool well at all especially in hotter temps over 90 degrees
Has anyone heard of this a do you recommend going to a larger condenser? They told us to put a push fan on it. There is only ½” between the Hood & Condenser with the hood open so there is not much room for a fan. So I don’t think a fan will fit. Do you know of a heavy duty Condenser that would work on this car?
Le Mans Master
Joined: Aug 2010
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Last edited by oldalaskaman; Jul 7, 2013 at 07:20 PM.
Melting Slicks
Joined: May 2002
Posts: 2,717
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From: Sulphur LA
St. Jude Donor '05-'06,'11,'13-'14,'16,'18,'19,'24, '25
1981 Chevy Corvette 32 k mile all original, except for the AC.
Just converted everything to R134, new Compressor, Condenser & Dryer. Compressor head pressure is running around 270 to 300, should be around 240. Mechanic said the stock condenser for the old R12 systems are not big enough to handle the heat generated by R134. So the car does not cool well at all especially in hotter temps over 90 degrees
Has anyone heard of this a do you recommend going to a larger condenser? They told us to put a push fan on it. There is only ½” between the Hood & Condenser with the hood open so there is not much room for a fan. So I don’t think a fan will fit. Do you know of a heavy duty Condenser that would work on this car?
Just converted everything to R134, new Compressor, Condenser & Dryer. Compressor head pressure is running around 270 to 300, should be around 240. Mechanic said the stock condenser for the old R12 systems are not big enough to handle the heat generated by R134. So the car does not cool well at all especially in hotter temps over 90 degrees
Has anyone heard of this a do you recommend going to a larger condenser? They told us to put a push fan on it. There is only ½” between the Hood & Condenser with the hood open so there is not much room for a fan. So I don’t think a fan will fit. Do you know of a heavy duty Condenser that would work on this car?
What was the suction pressure?
How much Freon did you put in the system?
Are you using the factory clutch driven fan and are the core support seals in good shape?
A good number of members here have been able to get the conversion to work for them without changing the condenser to a cross flow condenser like the newer cars.
Don’t see where you pulled and cleaned the orifice tube,
Sorry for all the questions but the answers are needed to help us understand what was done and how it was done.
Neal
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
I was gonna ask that one too. Although I'll be pedantic and say "R-134a" rather than R-12/Freon.
R-134A setups use less refrigerant by lb than R-12 setups, IIRC when converting you use 80% of the original value, but I'd need to look it up so don't quote me on that.
R-134A setups use less refrigerant by lb than R-12 setups, IIRC when converting you use 80% of the original value, but I'd need to look it up so don't quote me on that.
Racer
Joined: Sep 2009
Posts: 437
Likes: 3
From: Alvin Texas
It looks as if you have everything. This is the procedure I have always used; after evacuation of about 45 minutes or an hour I add the refrigerant to the High side until the until both pressures are equal. Close the valves on the gauge set, jump the clutch cycle switch, start the engine and run at 1500rpm,, turn on the A/C, charge through the Low side. I generally charge the High pressure to 2 times ambient temp + 20 psi. The low side should be 15#-25#. Duct temp should be 40*-50*. The clutch switch is adjustable by a screw between the terminals, turning the screw CCW lowers the pressure the compressor cycles off, I set mine at 25# on the low side to prevent freezing.
Hope this helps; It should take about 2 cans (20-24ozs) of R134a with a leak detector dye. I DO NOT use 134a with a leak sealer.
Your 81 should an auxiliary fan behind the radiator, it comes on around 230*, it's switch is on the R cyl head and provides the ground to control that fan. I turn this on at a lower temp you could install an aux fan control.
I live on the Texas Golf Coast, this works for me.
Butch
Hope this helps; It should take about 2 cans (20-24ozs) of R134a with a leak detector dye. I DO NOT use 134a with a leak sealer.
Your 81 should an auxiliary fan behind the radiator, it comes on around 230*, it's switch is on the R cyl head and provides the ground to control that fan. I turn this on at a lower temp you could install an aux fan control.
I live on the Texas Golf Coast, this works for me.
Butch
Le Mans Master
Joined: Aug 2010
Posts: 9,272
Likes: 17
It looks as if you have everything. This is the procedure I have always used; after evacuation of about 45 minutes or an hour I add the refrigerant to the High side until the until both pressures are equal. Close the valves on the gauge set, jump the clutch cycle switch, start the engine and run at 1500rpm,, turn on the A/C, charge through the Low side. I generally charge the High pressure to 2 times ambient temp + 20 psi. The low side should be 15#-25#. Duct temp should be 40*-50*. The clutch switch is adjustable by a screw between the terminals, turning the screw CCW lowers the pressure the compressor cycles off, I set mine at 25# on the low side to prevent freezing.
Hope this helps; It should take about 2 cans (20-24ozs) of R134a with a leak detector dye. I DO NOT use 134a with a leak sealer.
Your 81 should an auxiliary fan behind the radiator, it comes on around 230*, it's switch is on the R cyl head and provides the ground to control that fan. I turn this on at a lower temp you could install an aux fan control.
I live on the Texas Golf Coast, this works for me.
Butch
Hope this helps; It should take about 2 cans (20-24ozs) of R134a with a leak detector dye. I DO NOT use 134a with a leak sealer.
Your 81 should an auxiliary fan behind the radiator, it comes on around 230*, it's switch is on the R cyl head and provides the ground to control that fan. I turn this on at a lower temp you could install an aux fan control.
I live on the Texas Golf Coast, this works for me.
Butch
Thread Starter
6th Gear
Joined: Feb 2013
Posts: 6
Likes: 0
AC problems, new parts no cool.
Guys, after reading and printing out all of your replies, I will take to my mechanic. Am I reading this correctly that you do not think that this problem is the condenser coil?Our mechanic suggested adding another fan, or can we add a relay that will kick the fan on when the compressor comes on? Or do you feel this mechanic doesn't know how to charge this system correctly? Thank you for all of your input on this problem. Nona.
Safety Car
Joined: Mar 2007
Posts: 3,518
Likes: 37
I have a similar problem. 1977 September build. Had it looked at by a shop that does some AC. They put a kit on and changed it to 134. Tried to charge it but the compressor leaked. He put on a new compressor and charged it. It now has some cool air but very weak cooling, not weak fan but not cold.
I did my own complete compressor change including changing the orifice tube and drier, cleaning etc and bringing it in for charge. On my C5. Did that 2 years ago and it still blows low 40 degree like a champ. So I asked the guy why aren't you changing the orifice and drier? He said it is not needed in the older systems they are simpler than the new ones.
My questions are on the C3 is there an orifice tube and could it help to change it and recharge? Beside taking it to a real pro AC shop any other advise?
I did my own complete compressor change including changing the orifice tube and drier, cleaning etc and bringing it in for charge. On my C5. Did that 2 years ago and it still blows low 40 degree like a champ. So I asked the guy why aren't you changing the orifice and drier? He said it is not needed in the older systems they are simpler than the new ones.
My questions are on the C3 is there an orifice tube and could it help to change it and recharge? Beside taking it to a real pro AC shop any other advise?
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Le Mans Master
Joined: Oct 2006
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From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
There IS an orifice. Has to be. The older systems used the VIR, kind of a hard way to get there, but it did basically the same thing as the later model orifice. IF it gets plugged or restricted more than it's supposed to be, or not there, no cold air.
Race Director
Joined: Mar 2006
Posts: 14,112
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From: Florida
Nona
Hard to tell whats going on without the low side pressures. At 90° ambient, that is not all that high a pressure.
High pressure can be from overfill, bad condenser/dirty, bad clutch fan, wet system, air in system, too much oil.
Best is to wire your electric fan to always run with the a/c.
Your mechanic is basically right about the condenser. Despite the fact that some are satisfied using the original one, installing a large "parallel flow" condenser will ALWAYS produce colder air, but that is not your immediate problem.
Make sure he replaced the orifice tube and evacuates it for at least an hour min with a good (two stage) pump.
Bad part is that you almost have to start over from scratch for some of the symptoms.
Hard to tell whats going on without the low side pressures. At 90° ambient, that is not all that high a pressure.
High pressure can be from overfill, bad condenser/dirty, bad clutch fan, wet system, air in system, too much oil.
Best is to wire your electric fan to always run with the a/c.
Your mechanic is basically right about the condenser. Despite the fact that some are satisfied using the original one, installing a large "parallel flow" condenser will ALWAYS produce colder air, but that is not your immediate problem.
Make sure he replaced the orifice tube and evacuates it for at least an hour min with a good (two stage) pump.
Bad part is that you almost have to start over from scratch for some of the symptoms.