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So I’m trying to charge the A/C in my 78 corvette and there’s no Freon left in it at all, therefore the compressor clutch will not engage so I have hot wired the compressor to come on so that it will take my first can of Freon but it still won’t take any Freon. When I hook the hose up and crack the Freon can open the needle spikes from 0 to 100 and just sits there while the car is running at 1500 rpm and compressor running. I asked the guy who I got the charge kit from about it and he said the can has 100 pounds of pressure so it will show that on the gauge until you get the first can into the system but the system will not take any Freon, I held the can with it open for 20 minutes car and compressor running and all and it simply won’t take Freon so my question is why? What do I need to look for now?
The schrader core is either damaged or not being pressed in all way by the brass fitting on your hose.
If it's been "converted" to 134a, whatever adapter they used is most likely bad.
Either way, if there really is zero pressure in the system, you should pull a proper vacuum before charging it...better if you also replace the desiccant.
Aero is correct, if your system is empty then there is no possible way to charge it without a vacuum. You will probably need a new dryer also. However, if there is truly no freon in it then you need to determine why, otherwise any you put in will simply leak out. Probably easier to take it to a shop and let them look at it.
If the system is empty pressure test first with a bottle of Nitrogen to check for leaks; then draw and hold a vacuum to dry out the system; now it’s ready for oil/refrigerant charge. If it’s partly charged and has a slow leak it will still need to be drained and dismantled to fix.
You have to evacuate the system of all air and moisture before charging it. Otherwise, the moisture in there will freeze when cooled and give you BIGGER problems.
If the system is empty pressure test first with a bottle of Nitrogen to check for leaks; then draw and hold a vacuum to dry out the system; now it’s ready for oil/refrigerant charge. If it’s partly charged and has a slow leak it will still need to be drained and dismantled to fix.
I think drawing a vacuum and seeing if it holds for an hour will accomplish the same thing as the nitrogen. Not many of us have nitrogen around the house.
If the system is empty pressure test first with a bottle of Nitrogen to check for leaks; then draw and hold a vacuum to dry out the system; now it’s ready for oil/refrigerant charge. If it’s partly charged and has a slow leak it will still need to be drained and dismantled to fix.
even compressed air to check for leaks as they show much faster..and see how it holds.. then draw down with vacuum to remove moisture and see if it holds... personally i like to verify overnight vacuum AFTER the compressed air check..and that also lets any moisture boil out..
if system open for long time then for sure replace accumulator/ desiccant.. which is a
big PITA
Last edited by interpon; Aug 23, 2021 at 05:22 PM.
Where in the US are you in case someone near can help?
The orifice tube should be removed after evacuating the system to check for debris. If the system isn't taking in refrigerant then it could be blocked. That will ruin the compressor if it already isn't. The orifice tube will be full of gray/black gunk if the compressor has failed. Then it is time to properly flush the entire system, replace the compressor, orifice tube, and accumulator (and correct oil) plus new o-ring seals suitable for the refrigerant type, and vacuum. If it holds vacuum for a couple of hours then you can move forward with the charge.
Where in the US are you in case someone near can help?
The orifice tube should be removed after evacuating the system to check for debris. If the system isn't taking in refrigerant then it could be blocked. That will ruin the compressor if it already isn't. The orifice tube will be full of gray/black gunk if the compressor has failed. Then it is time to properly flush the entire system, replace the compressor, orifice tube, and accumulator (and correct oil) plus new o-ring seals suitable for the refrigerant type, and vacuum. If it holds vacuum for a couple of hours then you can move forward with the charge.
I was going to suggest this but honestly didn't know if it had one or if it was replaceable. This could be the entire issue actually.
I agree with interpon.. Pressure testing with compressed with air is not ideal, but it is ok since you’ll have to evacuate the system anyway.
The factory install would require the completion of a pressure test and evaluation before moving forward to the evacuation of ambient gasses and system charge.
Since the refrigerant is gone, air saturated with moisture has ben drawn into the system to replace the leaked gas. From the perspective of the refrigeration cycle, once the air is in your system the refrigerant circuit is contaminated.
As for system evacuation, I would run the vacuum pump for a minimum of an hour, and then let it sit for 30 minutes to insure there is no leakage.
But if you have time available, let the vacuum pump run overnight. Evacuating the system is nonlinear, and it can take hours or even days to get all the moisture and ambient gasses completely out of the system. And the more air and moisture you get out, the more space is available for the refrigerant.
metal line going from condenser in front of the radiator to the evaporator in the firewall. the fitting on the evap is where the orifice tube is located. https://www.ebay.com/itm/28385510349...IaAqF2EALw_wcB the rear fitting in the pic. the drier needs replaced as it has been open to air so it is sucking up water. not why it is called a drier though. it collects liquid refrigerant so the compressor doesn't try to compress a liquid which never ends well. dryer. https://www.topflightautomotive.com/...kaAj1bEALw_wcB
now, you are saying freon. which is r12. even people with AC licenses don't use 12 any more. and can't get it. so i am assuming it is converted to R134. no ability to charge is usually the charge fitting. some are loctited on, but most come off easy. you are charging on the low side, correct?
now, you are saying freon. which is r12. even people with AC licenses don't use 12 any more. and can't get it. so i am assuming it is converted to R134. no ability to charge is usually the charge fitting. some are loctited on, but most come off easy. you are charging on the low side, correct?
EPA 609 certification is easy to get online after studying the supplied material and taking a test. R12 was easy to get on eBay, and nobody ever asked to see my certification. Both of my 78’s are charged with r12. Mac’s Radiator here in town evacuated the old r12 for $60; they quoted me $300 to put recycled r12 back in. Their price for overhauling ac was around $2000, so I did the rest. R134 is already obsolete, banned from use in new cars because it is also a greenhouse gas (not as potent as r12 in ozone depletion).
Vacuum it and close the manifold......I like to see if it holds for about 2 hours, after vacuuming for 15-30 minutes........if it holds, a fresh can will suck right in and start the compressor.
Make sure that you vacuum through the manifold and close the valve at the manifold (blue ****)........disconnect vacuum pump and hook up the r134a line with a can ready to go......tap it and purge refridgerant at the schreader below the sight glass.....this gets all the air out of the manifold.....then open everything and let er rip.....
I do so many here in Texas for friends and family that it is like muscle memory.....
Jebby
Last edited by Jebbysan; Aug 24, 2021 at 11:44 AM.
Make sure the fill valve is right and not clogged It's sounds to me like the freon isn't even leaving the can because the Schrader valve is clogged or not pushed all the way down
EPA 609 certification is easy to get online after studying the supplied material and taking a test. R12 was easy to get on eBay, and nobody ever asked to see my certification. Both of my 78’s are charged with r12. Mac’s Radiator here in town evacuated the old r12 for $60; they quoted me $300 to put recycled r12 back in. Their price for overhauling ac was around $2000, so I did the rest. R134 is already obsolete, banned from use in new cars because it is also a greenhouse gas (not as potent as r12 in ozone depletion).
love the way he charged you 60 bucks to remove the r12 he was gonna charge you 300 to put back. win win... for him!
now, you are saying freon. which is r12. even people with AC licenses don't use 12 any more. and can't get it. so i am assuming it is converted to R134. no ability to charge is usually the charge fitting. some are loctited on, but most come off easy. you are charging on the low side, correct?
Freon doesn't mean R12, it's just a trademark name for the Chemours Company who makes endless amounts of refrigerants, including 134a.
My license is so old, it's my social security number. I've been in the trade for over 30 years and use R12 in all my vehicles that require it. Not difficult to find and the demand is so little, it's not all that expensive in the grand scheme of things.
R22 used in older home A/C systems is now over $1,000 a keg. 410a which was the more ozone friendly replacement went from $89 a keg just a few months ago to over $400 when I bought it last week.
Now is probably a good time to start stocking up on 134a. It's going to be going the way of R12 real soon.
A/C won’t charge
even compressed air to check for leaks as they show much faster..and see how it holds.. then draw down with vacuum to remove moisture and see if it holds... personally i like to verify overnight vacuum AFTER the compressed air check..and that also lets any moisture boil out..
