AC help needed
Thread Starter
Burning Brakes
Joined: Sep 2019
Posts: 923
Likes: 155
From: North Port, FL
AC help needed
Hello
New C3 owner long time Vette owner here, and I will be asking alot of questions as I go thru repairing and replacing stuff on my new to me 72 coupe.
It is an excellent 1 owner 120K mile car that has been well cared for and sat in an AConditioned garage in Calif for the past 50 or so years.
Pretty much in the same condition as it left the factory. I dont want to be the one to screw it up, but I plan on some stuff that will hopefully
improve what GM designed.
My current problem is the AC compressor keeps cycling off and on and I need to fix it here in Phoenix in the summer time. I'm thinking a bad clutch
but wonder what else could it be? Any at home tests I might try?
TIA
Dan
New C3 owner long time Vette owner here, and I will be asking alot of questions as I go thru repairing and replacing stuff on my new to me 72 coupe.
It is an excellent 1 owner 120K mile car that has been well cared for and sat in an AConditioned garage in Calif for the past 50 or so years.
Pretty much in the same condition as it left the factory. I dont want to be the one to screw it up, but I plan on some stuff that will hopefully
improve what GM designed.
My current problem is the AC compressor keeps cycling off and on and I need to fix it here in Phoenix in the summer time. I'm thinking a bad clutch
but wonder what else could it be? Any at home tests I might try?
TIA
Dan
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
generally that is low refrigerant. runs until the suction-lpw pressure-side pressure drops too low then shuts off. soon as it shuts off the pressure rises until it says it is good and fires up again. is it still r12? or r134. get this.
Last edited by derekderek; May 29, 2021 at 02:35 PM.
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
or a cheapo real gauge set. which also works for r 12.
the system is charged to around 40 to 70 psi or so when not running. when compressor starts, low side drops to about 25-40 psi. if it drops too low compressor shuts off. them pressure rises and low pressure safety disengages and it starts again. now, a blockage can cause high pressure limit switch to also make system cycle. but low level more likely. a slight leak can be pricey to find and repair. if a weekend car, it may be more cost effective to add enough refrigerant to make the system happy for the day or few hours as opposed to paying hundreds and finding the leak is still there...
Last edited by derekderek; May 29, 2021 at 02:38 PM.
Thread Starter
Burning Brakes
Joined: Sep 2019
Posts: 923
Likes: 155
From: North Port, FL
or a cheapo real gauge set. which also works for r 12. https://www.amazon.com/R134a-Manifol...a-779844550016 the system is charged to around 40 to 70 psi or so when not running. when compressor starts, low side drops to about 25-40 psi. if it drops too low compressor shuts off. them pressure rises and low pressure safety disengages and it starts again. now, a blockage can cause high pressure limit switch to also make system cycle. but low level more likely. a slight leak can be pricey to find and repair. if a weekend car, it may be more cost effective to add enough refrigerant to make the system happy for the day or few hours as opposed to paying hundreds and finding the leak is still there...
Try that first.
Melting Slicks
Joined: Sep 2006
Posts: 2,810
Likes: 469
From: Wichita Kansas
I was not aware that the '72 would cycle on and off. Hmmmm I thought if it got too low on freon and caused the compressor distress, that the thermolimiter switch would melt to save the compressor....
Thread Starter
Burning Brakes
Joined: Sep 2019
Posts: 923
Likes: 155
From: North Port, FL
I just drove across the desert from LA to Phoenix and it was going off and on the whole way. Completly stock AC system
Le Mans Master
Joined: Jun 2019
Posts: 7,649
Likes: 2,466
From: Indiana
I would get some gauges..first step for anything..
doubtful though you can loan r12...rare...
you are too far for me to loan
might be good to take a pic of fittings...just to be sure r12 fittings...
doubtful though you can loan r12...rare...
you are too far for me to loan
might be good to take a pic of fittings...just to be sure r12 fittings...
Le Mans Master
Joined: Mar 2004
Posts: 7,465
Likes: 1,485
From: Little Rock AR
They click on and off on low charge. After all those years the seals are shot. R12 leaked out.
I am resealing mine now. Bought the green O-ring kit from Zip and the compressor seals/tools from Century Auto Air. Guage set from Toolsource. We have a case of R12 that I aquired years ago. Almost ready. Need a new accumuator dryer and vacuum pump then just get after it.
I am resealing mine now. Bought the green O-ring kit from Zip and the compressor seals/tools from Century Auto Air. Guage set from Toolsource. We have a case of R12 that I aquired years ago. Almost ready. Need a new accumuator dryer and vacuum pump then just get after it.
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Burning Brakes
Joined: Oct 2001
Posts: 918
Likes: 198
From: TX
They click on and off on low charge. After all those years the seals are shot. R12 leaked out.
I am resealing mine now. Bought the green O-ring kit from Zip and the compressor seals/tools from Century Auto Air. Guage set from Toolsource. We have a case of R12 that I aquired years ago. Almost ready. Need a new accumuator dryer and vacuum pump then just get after it.
I am resealing mine now. Bought the green O-ring kit from Zip and the compressor seals/tools from Century Auto Air. Guage set from Toolsource. We have a case of R12 that I aquired years ago. Almost ready. Need a new accumuator dryer and vacuum pump then just get after it.
If you have a stock 69 system I would put in a new expansion valve, too. They are cheap. Got my accumulator and valve from Old Air.
VS
Le Mans Master
Joined: Mar 2004
Posts: 7,465
Likes: 1,485
From: Little Rock AR
I have a stock '80 system. My plan is to keep it original as possible but fully functional. I know the history so that helps. No component failures that I know about. If it holds vacuum, it should work.
Thread Starter
Burning Brakes
Joined: Sep 2019
Posts: 923
Likes: 155
From: North Port, FL
So just some juice might be all I need. I'll try that and some dye first.
Le Mans Master
Joined: Mar 2004
Posts: 7,465
Likes: 1,485
From: Little Rock AR
The new green o-rings are pretty darn cheap and so is a compressor overhaul. The currently available replacement compressors are kind of suspect these days. I know my o-ring seals are 40 years old so a basic system overhaul is cheap insurance here. If R12 gets crazy expensive in the future the system will already have 134a compatible seals. I plan to stick with mineral oil for now. Flush it out if or when it's time to convert. That is the plan so far.
Thread Starter
Burning Brakes
Joined: Sep 2019
Posts: 923
Likes: 155
From: North Port, FL
If you can afford the 3 lbs of R12 just to test it? You do know you have a slow leak somewhere right now. If it leaks out fast after you fill it you are still doing a re-seal, evacuate and recharge later. Judgement call there.
The new green o-rings are pretty darn cheap and so is a compressor overhaul. The currently available replacement compressors are kind of suspect these days. I know my o-ring seals are 40 years old so a basic system overhaul is cheap insurance here. If R12 gets crazy expensive in the future the system will already have 134a compatible seals. I plan to stick with mineral oil for now. Flush it out if or when it's time to convert. That is the plan so far.
The new green o-rings are pretty darn cheap and so is a compressor overhaul. The currently available replacement compressors are kind of suspect these days. I know my o-ring seals are 40 years old so a basic system overhaul is cheap insurance here. If R12 gets crazy expensive in the future the system will already have 134a compatible seals. I plan to stick with mineral oil for now. Flush it out if or when it's time to convert. That is the plan so far.
Le Mans Master
Joined: Mar 2004
Posts: 7,465
Likes: 1,485
From: Little Rock AR
I used to be in the HVAC business years ago. We had techs with certification so it was not hard to get at that time. I have retired from that business so I would not know where to find any more. If you find some, use it sparingly.
Burning Brakes
Joined: Aug 2007
Posts: 894
Likes: 244
From: Green Valley Ca
Le Mans Master
Joined: Jun 2019
Posts: 7,649
Likes: 2,466
From: Indiana
Please do not open system yet..
you need gauges first..
are you sure its r12? Did it work before? Gauges and a small investment may last a year..it may last a day...no foul yet...
lets go with what we know first..
r-12 ebay and craigslist is where i get mine..but lets be sure you know what you have first...pics of fittings ?
you need gauges first..
are you sure its r12? Did it work before? Gauges and a small investment may last a year..it may last a day...no foul yet...
lets go with what we know first..
r-12 ebay and craigslist is where i get mine..but lets be sure you know what you have first...pics of fittings ?
Last edited by interpon; May 30, 2021 at 04:57 PM.
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
R 12 fittings look like tire valves. R 134 fittings look like air hose quick disconnects. snap a pic of your fittings but this should answer. if 134, a 20 buck charging hose with gauge in it will do the trick. snap it on. see what pressure is. start car and run ac. you will see the pressure drop when compressor fires and climb when it shuts off. post all 3 readings. if r12, get the 29 buck gauge set. you can't get r 12 but you can go to an HVAC guy sounding like you know what you need, and a screwin is not part of it...