A/C Compressor problem
Thread Starter
Heel & Toe
Joined: Nov 2013
Posts: 22
Likes: 1
From: Hazlet NJ
A/C Compressor problem
Hello everyone!
I have a 78 L48 Pace Car that is blowing warm air out of the vents when Max/Norm A/C switch is on. I checked the compressor and it is turning with the belt while engine is running. However, the clutch does not engage when the A/C switch is on. If the unit needs a recharge would this be the cause of the clutch not engaging? Clutch will not budge by hand. Can the clutch be replaced without replacing the whole compressor and can you still recharge with R12? or is a conversion to R134a in order?
Thanks in advance, Jim
I have a 78 L48 Pace Car that is blowing warm air out of the vents when Max/Norm A/C switch is on. I checked the compressor and it is turning with the belt while engine is running. However, the clutch does not engage when the A/C switch is on. If the unit needs a recharge would this be the cause of the clutch not engaging? Clutch will not budge by hand. Can the clutch be replaced without replacing the whole compressor and can you still recharge with R12? or is a conversion to R134a in order?
Thanks in advance, Jim
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,170
From: Hermosa
The clutch will not engage unless there is enough freon in the system to satisfy the low pressure switch.
R-12 is still available , but expensive.
Changing to 134a is possible, but involved and still takes some $$$ and time.
The clutch can be changed independent of the compressor. If you put 12 volts to the plug on the compressor you should hear the clutch click. It's just an electro magnet to activate the clutch.
R-12 is still available , but expensive.
Changing to 134a is possible, but involved and still takes some $$$ and time.
The clutch can be changed independent of the compressor. If you put 12 volts to the plug on the compressor you should hear the clutch click. It's just an electro magnet to activate the clutch.
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
Can you turn the center of the clutch by hand? Engine off. IF the center is locked then your compressor is most likely toast. Could be the front clutch bearing, but the odds of that are not in your favor.
Le Mans Master
Joined: May 2007
Posts: 5,009
Likes: 1,116
From: North tonawanda NY
I converted my 74 original ac over to r134a 3 years ago for about $50... They do make additives to make the r12 lubrication oil compatible with r134a and the recharge/conversion kit I bought at advance auto had a form of stopleak in it which must have sealed the hoses since I read here somewhere that they are normally too porous for R134a. That said I understand everyone's mileage may vary.
Thread Starter
Heel & Toe
Joined: Nov 2013
Posts: 22
Likes: 1
From: Hazlet NJ
Thread Starter
Heel & Toe
Joined: Nov 2013
Posts: 22
Likes: 1
From: Hazlet NJ
A/C compressor problem
The clutch will not engage unless there is enough freon in the system to satisfy the low pressure switch.
R-12 is still available , but expensive.
Changing to 134a is possible, but involved and still takes some $$$ and time.
The clutch can be changed independent of the compressor. If you put 12 volts to the plug on the compressor you should hear the clutch click. It's just an electro magnet to activate the clutch.
R-12 is still available , but expensive.
Changing to 134a is possible, but involved and still takes some $$$ and time.
The clutch can be changed independent of the compressor. If you put 12 volts to the plug on the compressor you should hear the clutch click. It's just an electro magnet to activate the clutch.
Jim
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,170
From: Hermosa
If you want to test to see if the pump is seized or not you can bypass the low pressure switch by applying 12v directly to the compressor clutch with the engine running.
Do it in such a way that you can immediately remove the 12v in the event that it is seized. Also in a way that you are clear of rotating parts. Using the original plug and tapping into the wires upstream might be a way to do it safely.
If it is seized you're gonna hear an awful lot of noise when the clutch engages and tries to turn the compressor.
If it's not seized the compressor will run fine. Don't try to cool the car that way though. It needs the freon to help move the oil through the compressor, so running it with too low of freon would also present a lack of lubrication to the compressor and ruin it if you continued to operate it that way.
Last edited by REELAV8R; May 23, 2014 at 03:31 PM.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
Advanced
Joined: Jul 2013
Posts: 52
Likes: 0
From: Crawfordsville Indiana
Okay fellow's I have some a related question. I took my 78 SA in to have the A/C charged to see what all needed to be replaced. The did the retro fit, and charged the system to find that my compressor was leaking bad and needed replaced. To get the parts and labor warranty I had to replace the dryer and oriphsis, or however it is spelled. The hose would not come off the dryer so they replace that too. $966.00 later!
I have a whole new A/C system except the condinser which was in good shape. So the new system works and it blows cold air, I wish it blew a bit harder, but I may end up replacing the switch and blower at a later date.
My question is, when the ac is on and the car is in idle the ac compressor makes a noise it is like a tink noise every few seconds. Thoughts? When you accelerate it goes away, I don't want to ruin anything.
I noticed i lose a fair bit of power with the ac on but I supposed that is to be expected. Any and all thoughts are always appreciated.
I have a whole new A/C system except the condinser which was in good shape. So the new system works and it blows cold air, I wish it blew a bit harder, but I may end up replacing the switch and blower at a later date.
My question is, when the ac is on and the car is in idle the ac compressor makes a noise it is like a tink noise every few seconds. Thoughts? When you accelerate it goes away, I don't want to ruin anything.
I noticed i lose a fair bit of power with the ac on but I supposed that is to be expected. Any and all thoughts are always appreciated.
Advanced
Joined: Jul 2013
Posts: 52
Likes: 0
From: Crawfordsville Indiana
I figured it out, it was the belt slapping the brace at the bottom where that little belt "skip pad" is located.
Does anybody know if there is a newer ac bracket for these that fit the new compressor's better. I have it as tight as the current bracket allow's. I am planning on a new set of belts when I do the water pump next anyway!
Thanks
Does anybody know if there is a newer ac bracket for these that fit the new compressor's better. I have it as tight as the current bracket allow's. I am planning on a new set of belts when I do the water pump next anyway!
Thanks
Instructor
Joined: Dec 2011
Posts: 197
Likes: 27
From: New Jersey
My a/c belt did the same thing at idle and what I never put back on when I had the valve covers off was the bracket that went from the back of the compressor to the intake manifold bolt. Without that bracket the compressor was shaking no matter how tight I made the belt. Of course that's if your bracket is missing.
Advanced
Joined: Jul 2013
Posts: 52
Likes: 0
From: Crawfordsville Indiana
So I am wondering if there is a different bracket that is supposed to be used with the new A/C compressor I bought. It lines up with the other pulley's in the system, but is not as long on the back side as the old one was. The belt is as tight as I can get it. Even know the lower, belt guide is disconnected, and pushed down and out of the way, I am assuming the repair guy did this for clearance, it is now tapping on it again and making that sound again. It makes me wonder if this new A/C compressor is supposed to be uses with a different bracket. I do not know how old the belts are, but there isn't any dry rot and it looks good and feels tight.
Any Advice would be much appreciated.
Thanks again.
Brent
Any Advice would be much appreciated.
Thanks again.
Brent
7th Gear
Joined: Jun 2014
Posts: 7
Likes: 1
From: Trenton TN
I did this same job myself on my 78. I replaced the blower and fan wheel while I had the drier out. The wheel was cracked and warped. It looked near impossible to change it with drier in there. Pull your glove box and check your duct work in the dash. Mine was leaking and blowing all the cold air in there keeping the instruments nice and cool! I used duct tape to seal them up and get much better airflow now.
Last edited by zoomee; Jun 26, 2014 at 01:10 PM.
Drifting
Joined: Aug 2005
Posts: 1,443
Likes: 65
From: Wauconda IL
GM went backwards IMO when they moved from the A-6 to the R-4 style compressors. The A-6 was bulletproof but it was heavy and required a lot of power to run. The R-4 is smaller and somewhat more efficient power-wise but is fragile. I seem to replace R-4 compressors as often as I replace brakes on some cars-
R-134a with an R-4 is not something I would run on a vehicle that is driven regularly as the higher pressures required for R-134a will make an already fragile compressor weaker yet.
Can it be done? Sure....
Personally, if I was going to switch to R-134a, I'd follow through and replace the hoses, install a Sanden compressor and install a parallel flow condenser. Anything short of that is a compromise.
Just my .02
R-134a with an R-4 is not something I would run on a vehicle that is driven regularly as the higher pressures required for R-134a will make an already fragile compressor weaker yet.
Can it be done? Sure....
Personally, if I was going to switch to R-134a, I'd follow through and replace the hoses, install a Sanden compressor and install a parallel flow condenser. Anything short of that is a compromise.
Just my .02