AC Rebuilding Question?
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FTE Legend
Joined: Nov 2015
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From: Angier, NC
My overinflated thoughts:
Any AC system is designed to operate with a fixed amount of refrigerant, plus/minus a certain margin. Because the volume changes so much with temperature, the amount is determined by weight. Sounds daunting having to weigh the stuff, but it's not really necessary to be so precise. Those small cans are 12 ounces (weight, not volume as in fluid ounces). I've always guesstimated on getting 11 ounces per can (you can't get every last bit) and then reaching the desired total weight by guessing on a fraction of the final can. For any R134a conversion, a good rule of thumb is 80% of the R12 capacity.
is this method close enough? 38F air from the center vent, you decide for yourself.
Personally, I'm not a fan of filling by pressure. There are just so many variables, especially airflow through the condenser and ambient air temperature. If all components are in perfect condition, I guess it can be done. But let's throw in a common fault, like a little moisture in the system or a slipping compressor clutch. Fill to pressure now and the refrigerant amount could be all over the place, high or low. Besides the original fault, now you've got an unknown quantity of refrigerant to add confusion. You could end up chasing your tail when troubleshooting. Hopefully you will get suspicious by the third compressor.
That's why I like to fill by weight, so you know you've at least got the correct amount if you have to do any troubleshooting. And my weight guesstimation method seems to be reasonably accurate, no scales or special equipment required.
Any AC system is designed to operate with a fixed amount of refrigerant, plus/minus a certain margin. Because the volume changes so much with temperature, the amount is determined by weight. Sounds daunting having to weigh the stuff, but it's not really necessary to be so precise. Those small cans are 12 ounces (weight, not volume as in fluid ounces). I've always guesstimated on getting 11 ounces per can (you can't get every last bit) and then reaching the desired total weight by guessing on a fraction of the final can. For any R134a conversion, a good rule of thumb is 80% of the R12 capacity.
is this method close enough? 38F air from the center vent, you decide for yourself.
Personally, I'm not a fan of filling by pressure. There are just so many variables, especially airflow through the condenser and ambient air temperature. If all components are in perfect condition, I guess it can be done. But let's throw in a common fault, like a little moisture in the system or a slipping compressor clutch. Fill to pressure now and the refrigerant amount could be all over the place, high or low. Besides the original fault, now you've got an unknown quantity of refrigerant to add confusion. You could end up chasing your tail when troubleshooting. Hopefully you will get suspicious by the third compressor.
That's why I like to fill by weight, so you know you've at least got the correct amount if you have to do any troubleshooting. And my weight guesstimation method seems to be reasonably accurate, no scales or special equipment required.
I know by weight is the way they want R134A done but if you don't have that kind of setup you go with the next best .......... by PSI / Temp.
Dave ----
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FTE Legend
Joined: Nov 2015
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From: Angier, NC
WE ARE CHILLING! <smiley image="anim_jump.gif"/>
First I have to say thank you for all the help to get this working.
All readings are on the low side of system as I don't have the adaptor for the high side.
When I first checked static PSI it was 88 PSI @ 90*F and by the chart should be up around 104 - 114 PSI
When running, fan on high, RPM @ idle, large fan in front of condenser I had like 45 PSI, chart said 50 - 55 PSI.
I used a bucket of hot water on the cans and even emptied the 2 that had a little still in them.
The 3 first can did not bring it up to the 50 - 55 PSI so added a 4th and still not so a 5th went in.
That got it up to 58 PSI at idle and at about 2000 RPM came down to the 50 - 55 PSI reading.
Also when you unscrew the low side hose, some Freon comes out so I would say I am at 55 PSI.
So 5 - 12oz cans of Freon & 8oz to 10oz of Ester oil was needed to get my system working.
Oh an not too soon as the front fan, front / rear system, in the Durango stopped working this morning when I got in it at 1am to go to work.
I have replace the resister for the fan like 3 time & the pig tail to it once because it melted but the fan always worked on high. I hope the pig tail melted and why the fan does not work. I don't know where the fan motor is and what it would take to replace it?
Thanks again
Dave G
First I have to say thank you for all the help to get this working.
All readings are on the low side of system as I don't have the adaptor for the high side.
When I first checked static PSI it was 88 PSI @ 90*F and by the chart should be up around 104 - 114 PSI
When running, fan on high, RPM @ idle, large fan in front of condenser I had like 45 PSI, chart said 50 - 55 PSI.
I used a bucket of hot water on the cans and even emptied the 2 that had a little still in them.
The 3 first can did not bring it up to the 50 - 55 PSI so added a 4th and still not so a 5th went in.
That got it up to 58 PSI at idle and at about 2000 RPM came down to the 50 - 55 PSI reading.
Also when you unscrew the low side hose, some Freon comes out so I would say I am at 55 PSI.
So 5 - 12oz cans of Freon & 8oz to 10oz of Ester oil was needed to get my system working.
Oh an not too soon as the front fan, front / rear system, in the Durango stopped working this morning when I got in it at 1am to go to work.
I have replace the resister for the fan like 3 time & the pig tail to it once because it melted but the fan always worked on high. I hope the pig tail melted and why the fan does not work. I don't know where the fan motor is and what it would take to replace it?
Thanks again
Dave G
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Joined: Nov 2013
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First you must answer these questions:
Who is buried in Grant's tomb?
What color is the White House?
Who wrote Beethoven's 5th Symphony?
A 12 ounce can of refrigerant contains - drum roll please:
Twelve (12) ounces of refrigerant.
That's plain ordinary ounces, as in weight on a scale. Think 12 ounces of gold dust, measured by weight, not volume. Or 12 ounces of pretzels or flour, sold by weight not volume (contents may have settled during shipping). Three quarters of a pound, if you will. It's NOT fluid ounces, a common and confusingly named measure of liquid volume, as seen on a soda can for example.
Who is buried in Grant's tomb?
What color is the White House?
Who wrote Beethoven's 5th Symphony?
A 12 ounce can of refrigerant contains - drum roll please:
Twelve (12) ounces of refrigerant.
That's plain ordinary ounces, as in weight on a scale. Think 12 ounces of gold dust, measured by weight, not volume. Or 12 ounces of pretzels or flour, sold by weight not volume (contents may have settled during shipping). Three quarters of a pound, if you will. It's NOT fluid ounces, a common and confusingly named measure of liquid volume, as seen on a soda can for example.
Lead Driver
Joined: Nov 2013
Posts: 7,173
Likes: 1,173
The stock specs for factory AC is 3 pounds of R12, plus/minus a quarter of a pound. Remember, that's weight, not volume. That's 48 ounces of R12, plus/minus 4, so 44 to 52 ounces is your target range. With an R134a conversion, the general target is 80% of R12 specs. That's means you want 35 to 42 ounces of R134a. You've got about 60 ounces. Even with the upper end of the target range, you're about 50% over.
You may have something else going on with your AC system. Were you taking your readings while parked, with minimal airflow over the condenser? You're not going to see much cooling like that. Ideally, you really want to go for a test drive and gets lots of ram airflow through the condenser.
You may have shot yourself in the foot with such an overfill. Short of using fancy recovery equipment, there's no reasonable method to bleed off any of that overfill. I'd suggest starting over, refilling by weight, and going from there. Three 12 ounce cans will give you 36 ounces, at the low end of the target range. I usually use 3 and a half cans, which accounting for the little bit remaining in each can plus the manifold and hoses, puts me near the upper end of the target range.
Tuned
Joined: Dec 2019
Posts: 262
Likes: 37
From: East Tennessee
Dave, your system is SERIOUSLY overfilled.
The stock specs for factory AC is 3 pounds of R12, plus/minus a quarter of a pound. Remember, that's weight, not volume. That's 48 ounces of R12, plus/minus 4, so 44 to 52 ounces is your target range. With an R134a conversion, the general target is 80% of R12 specs. That's means you want 35 to 42 ounces of R134a. You've got about 60 ounces. Even with the upper end of the target range, you're about 50% over.
You may have something else going on with your AC system. Were you taking your readings while parked, with minimal airflow over the condenser? You're not going to see much cooling like that. Ideally, you really want to go for a test drive and gets lots of ram airflow through the condenser.
You may have shot yourself in the foot with such an overfill. Short of using fancy recovery equipment, there's no reasonable method to bleed off any of that overfill. I'd suggest starting over, refilling by weight, and going from there. Three 12 ounce cans will give you 36 ounces, at the low end of the target range. I usually use 3 and a half cans, which accounting for the little bit remaining in each can plus the manifold and hoses, puts me near the upper end of the target range.
The stock specs for factory AC is 3 pounds of R12, plus/minus a quarter of a pound. Remember, that's weight, not volume. That's 48 ounces of R12, plus/minus 4, so 44 to 52 ounces is your target range. With an R134a conversion, the general target is 80% of R12 specs. That's means you want 35 to 42 ounces of R134a. You've got about 60 ounces. Even with the upper end of the target range, you're about 50% over.
You may have something else going on with your AC system. Were you taking your readings while parked, with minimal airflow over the condenser? You're not going to see much cooling like that. Ideally, you really want to go for a test drive and gets lots of ram airflow through the condenser.
You may have shot yourself in the foot with such an overfill. Short of using fancy recovery equipment, there's no reasonable method to bleed off any of that overfill. I'd suggest starting over, refilling by weight, and going from there. Three 12 ounce cans will give you 36 ounces, at the low end of the target range. I usually use 3 and a half cans, which accounting for the little bit remaining in each can plus the manifold and hoses, puts me near the upper end of the target range.
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From: Virginia
My Tahoe has a front and rear system in it, and it only takes a little over 3 cans. But see how it works. In my experience the compressor will lock up and the belt will start squealing, or the high pressure blow off will pop. I have had that happen to me a couple of times with no serious permanent damage to the system. If the compressor locks up quickly turn the A/C off and it will stop.
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FTE Legend
Joined: Nov 2015
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From: Angier, NC
Ok with 3 cans, 36oz, it was cool NOT cold and I did drive it to work yesterday on the hottest day we have had yet.
Today I also had my big fan, not a box fan, blowing into the condenser.
Also by the 134a charts the low side should be between 50 - 55 PSI @ 95*f.
Before I added more the low side started at 45 PSI @ 95*f with the fan blowing in the condenser.
With just 1 can added, now 48oz, it just got up to 50 PSI but as soon as the RPM came up the PSI came down to 45 PSI or lower.
So I added the last can, 60oz total now, and the PSI cam up to about 58 PSI but I also knew when I pulled the hose off I would loose some PSI.
Also when you bring the RPM up the low side only goes down to about 50 PSI and it does blow cold not both sitting at lights and driving down the road.
I don't know what else could be "going on" with the system?
New condenser, new dryer, new orifice valve (old one was clean when pulled), 2 of the 3 hoses are new, flushed out the evap and the used compressor that seams to be working as it is cooling the truck down.
It would of been nice to know the high side but I could not at this time and unless something happens I don't plan to put the gauges back on it at this time.
I need to use it to get to work as my Durango HVAC front fan stopped working, no front AC.
Will let you know how it does.
Dave ----
Today I also had my big fan, not a box fan, blowing into the condenser.
Also by the 134a charts the low side should be between 50 - 55 PSI @ 95*f.
Before I added more the low side started at 45 PSI @ 95*f with the fan blowing in the condenser.
With just 1 can added, now 48oz, it just got up to 50 PSI but as soon as the RPM came up the PSI came down to 45 PSI or lower.
So I added the last can, 60oz total now, and the PSI cam up to about 58 PSI but I also knew when I pulled the hose off I would loose some PSI.
Also when you bring the RPM up the low side only goes down to about 50 PSI and it does blow cold not both sitting at lights and driving down the road.
I don't know what else could be "going on" with the system?
New condenser, new dryer, new orifice valve (old one was clean when pulled), 2 of the 3 hoses are new, flushed out the evap and the used compressor that seams to be working as it is cooling the truck down.
It would of been nice to know the high side but I could not at this time and unless something happens I don't plan to put the gauges back on it at this time.
I need to use it to get to work as my Durango HVAC front fan stopped working, no front AC.
Will let you know how it does.
Dave ----
Thread Starter
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FTE Legend
Joined: Nov 2015
Posts: 30,906
Likes: 4,122
From: Angier, NC
Dave, your system is SERIOUSLY overfilled.
The stock specs for factory AC is 3 pounds of R12, plus/minus a quarter of a pound. Remember, that's weight, not volume. That's 48 ounces of R12, plus/minus 4, so 44 to 52 ounces is your target range. With an R134a conversion, the general target is 80% of R12 specs. That's means you want 35 to 42 ounces of R134a. You've got about 60 ounces. Even with the upper end of the target range, you're about 50% over.
You may have something else going on with your AC system. Were you taking your readings while parked, with minimal airflow over the condenser? You're not going to see much cooling like that. Ideally, you really want to go for a test drive and gets lots of ram airflow through the condenser.
You may have shot yourself in the foot with such an overfill. Short of using fancy recovery equipment, there's no reasonable method to bleed off any of that overfill. I'd suggest starting over, refilling by weight, and going from there. Three 12 ounce cans will give you 36 ounces, at the low end of the target range. I usually use 3 and a half cans, which accounting for the little bit remaining in each can plus the manifold and hoses, puts me near the upper end of the target range.
The stock specs for factory AC is 3 pounds of R12, plus/minus a quarter of a pound. Remember, that's weight, not volume. That's 48 ounces of R12, plus/minus 4, so 44 to 52 ounces is your target range. With an R134a conversion, the general target is 80% of R12 specs. That's means you want 35 to 42 ounces of R134a. You've got about 60 ounces. Even with the upper end of the target range, you're about 50% over.
You may have something else going on with your AC system. Were you taking your readings while parked, with minimal airflow over the condenser? You're not going to see much cooling like that. Ideally, you really want to go for a test drive and gets lots of ram airflow through the condenser.
You may have shot yourself in the foot with such an overfill. Short of using fancy recovery equipment, there's no reasonable method to bleed off any of that overfill. I'd suggest starting over, refilling by weight, and going from there. Three 12 ounce cans will give you 36 ounces, at the low end of the target range. I usually use 3 and a half cans, which accounting for the little bit remaining in each can plus the manifold and hoses, puts me near the upper end of the target range.
My Tahoe has a front and rear system in it, and it only takes a little over 3 cans. But see how it works. In my experience the compressor will lock up and the belt will start squealing, or the high pressure blow off will pop. I have had that happen to me a couple of times with no serious permanent damage to the system. If the compressor locks up quickly turn the A/C off and it will stop.
60oz = 3.75 pounds if Google is right.
But at 3 cans it was only cool not cold and the low side PSI was to low.
Don't know what to say other than if it keeps me cool I am happy camper.
Dave ----
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Dave,
I'm glad to hear you got it working.
Enjoy your ride. If it works for now good for you. If you have a problem address it when it happens.
I prefer R12 in automotive ac systems. It runs at lower pressure's and cools at lower rpms.
I have sat in traffic for hours at a idle and still enjoyed cold air coming out of the vents.
Try that with R134a, not going to happen.
It's expensive to buy if you pay retail for it but I was lucky enough to purchase it in 30lb tanks back in the day.
Those that live in places like Arizona, Texas and Nevada still prefer it over 134a.
I've put it in newer systems and had no problems.
Too bad it's bad for the environment. But it's still used around the world today. Still manufactured in Mexico and India.
Believe me, it gets hot there but they don't have a restriction on it.
I'm glad to hear you got it working.
Enjoy your ride. If it works for now good for you. If you have a problem address it when it happens.
I prefer R12 in automotive ac systems. It runs at lower pressure's and cools at lower rpms.
I have sat in traffic for hours at a idle and still enjoyed cold air coming out of the vents.
Try that with R134a, not going to happen.
It's expensive to buy if you pay retail for it but I was lucky enough to purchase it in 30lb tanks back in the day.
Those that live in places like Arizona, Texas and Nevada still prefer it over 134a.
I've put it in newer systems and had no problems.
Too bad it's bad for the environment. But it's still used around the world today. Still manufactured in Mexico and India.
Believe me, it gets hot there but they don't have a restriction on it.
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FTE Legend
Joined: Nov 2015
Posts: 30,906
Likes: 4,122
From: Angier, NC
I did buy a 30 lb tank when they first put a restriction on it but left it with a guy that had equipment to install it up north and that was 20+ years ago.
I will give this a try and if a problem comes up just deal with it.
Dave ----
I will give this a try and if a problem comes up just deal with it.
Dave ----
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From: Virginia
Thread Starter
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FTE Legend
Joined: Nov 2015
Posts: 30,906
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From: Angier, NC
Windows where down the whole time.
It was pretty chilly going to work this morning even with the fan on low.
Hope the door hinge did not break. Lost some air flow out yhe vents about half way to work.
Did not feel it coming out defrost or floor so don't know where it could be going?
Dave ----
It was pretty chilly going to work this morning even with the fan on low.
Hope the door hinge did not break. Lost some air flow out yhe vents about half way to work.
Did not feel it coming out defrost or floor so don't know where it could be going?
Dave ----
Tuned
Joined: Dec 2019
Posts: 262
Likes: 37
From: East Tennessee
My system wasn’t completely empty but, it didn’t have very much in it IIRC. I agree with if it’s working drive it and enjoy cold air on these sweltering days. If it’s to full it’ll let you know and just turn the ac off if something does happen so I wouldn’t worry about it until then. Nice job making a none factory air into a factory air 
!!!
!!!
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FTE Legend
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From: Angier, NC
Air flow out the vent was good on the ride home from work so don't know what that was all about this morning?
Maybe with the fan on low, set to max AC and it being chilly in the cab the evap iced up?
Will have to keep an eye on that.
On the ride home I had to kick the fan down 1 setting from high as it was getting chilly in the cab, OAT was about 88*f.
Dave ----
Maybe with the fan on low, set to max AC and it being chilly in the cab the evap iced up?
Will have to keep an eye on that.
On the ride home I had to kick the fan down 1 setting from high as it was getting chilly in the cab, OAT was about 88*f.
Dave ----
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Joined: Jul 2020
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Factory air uses vacuum lines to control the vents.
Dealer installed ac uses cable controls to cut off heater duct.
Look for a dry rotted or broken vacuum line behind dash control. Outside under the hood on top of the box there is a vacuum actuator. It has a vacuum line that
Becomes weak overtime.
Dealer installed ac uses cable controls to cut off heater duct.
Look for a dry rotted or broken vacuum line behind dash control. Outside under the hood on top of the box there is a vacuum actuator. It has a vacuum line that
Becomes weak overtime.