wajulia

1981 - Finally got around to fixing my AC after it has been empty for 27years. I pulled a vacuum on it for about an hour. After 30 minutes it was still holding a vacuum. So I added three 6 oz cans of Enviro- Safe. I decided to use this instead of converting to r134. The instructions say that each can is equivalent to 18 oz of r12

After the first can, the compressor clutch came on ( I admit I was happily surprised). I put in the other two cans, compressor cycled nicely. I used an oil tester and it read low on oil, so I added 3 oz of oil.

Problem, the air from the dash is 60 deg. I am pretty sure the heater is not on, temp from the vent setting is the same temp as outside air

Static pressure on both sides is 80 psi

Operating pressures when cycling
Low side 25-45 psi
High side 180- 215 psi
Ambient temperature is about 80 deg
Low side pipe to the compressor is cold to the touch ( seems much colder than 60 deg)

Seems like the compressor is working correctly. Any ideas why the temperature is so high?

qwank

see what the temp is while driving down the highway, you might not be getting enough air flow through the condenser at idle

you need 2.75lbs of r12 or about 2.25lbs of r134

wajulia

The temperature is driving down the road.

If the markings on the can are correct that 6 oz of enviro-safe is equivalent to 18 oz of r12, I put an equivalent of 3.3 lbs in the system.

chevymans 77

according to the conversion for R12 vs Enviro-Safe your a little over charged but your pressures indicate your low on charge.

The low pressure switch is set to shut the compressor off around 18 to 22 psi. If the clutch is cycling then their is something else wrong after putting in 3 6oz cans of Enviro-Safe.

I've used Enviro-Safe Industrial 12 and was impressed with the vent temps.

what are the pressure readings sitting in the driveway idling with the AC on?

Is the compressor cycling while idling?

Neal

noonie

Don't know what the ambient temp is, but if your driving on a hot sunny day with a decent heat load and it is not in max mode (recirculating), then 60° isn't that bad a temp for an older car with for certain air leaks.

And before anyone says their temps are <40°, I could probably take this car and get it to read 38° without doing anything to the system.

TimAT

Could also be the evaporator has a bunch of trash on it. Again, airflow. Somehow all sorts of leaves, dirt, bugs, and paper finds it's way to the inside of the sir box.

speedreed8

i would still put a manual shutoff valve in one of the heater hoses.

Jud Chapin

I too would block off the heater. You can just take a pair of vice grips and squeeze one of the heater hoses for test purposes. Put something flat between the teeth to keep from damaging the hose. Another thing to check is the weather stripping at the rear of the hood. I believe the '81 came with one and if its missing or not sealing, hot air from the engine compartment will end up in your duct work raising a/c temps at the vents.

zwede

Do the later C3s not have one from the factory? My '71 has a heater shutoff valve that shuts water to the heater core off when the selector is on 'Max AC'.

The pressures look OK, maybe a bit low but I have no experience with the refrigerant you use.

On a 80F day I expect a C3 AC system to blow <50F out the vents @ idle.

Disconnecting/blocking the heater core is a good suggestion. Might be that your blend door is misaligned or leaking to where you always blow heated air out the vents.

wajulia

It cycles on idle but very long cycles, the clutch is on most of the time. At 2000 rpm it cycles about every 20 seconds

At idle low side about 35. High side around 220

I will try to check the evaporator

wajulia

I am very unsure about the oil. As I said, I put three oz in. Not sure what was already in it. Could there be to much oil. Could that cause this to happen?

mds3013

Please explain how the oil tester works. What type of oil did you put into the system? Envirosafe is a Hydrocarbon which means flammable as in Freeze12. Take that $h!t out and get some R-12. We sometimes make things harder than they need to be. If the compressor is not staying on all of the time until the interior gets to about 60 degrees then something is not right. You stated that the vent on cold is the same as ambient. Is this with a car up to operating temps.? If so, then you do not have a problem with the heater shut off valve or blend door. mike...

oldalaskaman

I have to ask the unasked question, how would you do it? many thanks, bob

qwank

same goes for the condenser.

wajulia

The oil tester I used is Pittstop AC oil analyzer

I used the enviro-safe oil charge 3. Safe for r12 systems

wajulia

The compressor should be on all the time? I thought it should cycle. It is practically on all the time at idle,, cycles every 30 seconds at 2000 rpm

noonie

I'm sure mds3013 was concerned about the amount of oil. there is no way to test for that. take it apart and drain each component and refill is the only way. Too much oil will reduce the amount of cooling.

noonie

Just the basics I mentioned before.
Here in S Florida, where the sun is brutal, the heat gain on a car in the open is amazing. Shoot a black dash with an IR gun that's been in the sunlite for awhile, even with the air on.

I can take a black car the has vent temps in the 50s or low 60s while driving and put it in the shade, windows rolled up, set on recirculate max, engine at >1500rpm and after about 15-20 minutes the center vent will be in the 30s. Wows people every time wondering why they can't get theirs that low.
Realistically, while driving, especially short distances, the vent temps will be close to 60.

How long does your house take to cool from 90 to 75. same thing.

AirborneSilva

Well shoot, where do you live? When I am able to get my AC stuff I want you to work on it for me never mind, just saw the post above!