AC Refrigerant Fill Method
05-23-2013, 04:55 PM
#1
Drifting
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AC Refrigerant Fill Method
This might be a stupid question, but ...............
What is the best way of ensuring that the AC system is properly filled with refrigerant?
a) Totally evacuate the system and fill it with the proper weight of the refrigerant.
b) Fill until there are no more bubbles seen in the sight glass.
c) A combination of the above.
What is the best way of ensuring that the AC system is properly filled with refrigerant?
a) Totally evacuate the system and fill it with the proper weight of the refrigerant.
b) Fill until there are no more bubbles seen in the sight glass.
c) A combination of the above.
05-23-2013, 05:04 PM
#2
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A.
Engine off, through the low side on an evacuated system. Hair dryer on the inverted bottle of refrigerant if you're not happy with the pace of filling.
Engine off, through the low side on an evacuated system. Hair dryer on the inverted bottle of refrigerant if you're not happy with the pace of filling.
05-23-2013, 05:45 PM
#3
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05-23-2013, 07:39 PM
#5
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If you fill via the low side (can upright, warm the can as needed to increase the gas pressure in the can), the engine needs to be running with the front and rear AC on full. The compressor should kick on once you start filling and the pressure rises above the low pressure cutoff. Once it does, it helps to raise the engine RPMs as this allows the compressor to suck the Freon charge from the low side more quickly.
05-23-2013, 07:44 PM
#6
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If you want to charge with liquid as described above, engine is off and cold. You can charge that way to either port, but it's probably safer to put liquid into the high-side port. Then let the system settle for a few minutes while you disconnect the bottle and hoses, so the liquid will completely flash to vapor in the system before you even think of starting the engine and running the compressor. THE BOTTLE MUST NOT BE CONNECTED TO THE HIGH-SIDE PORT WITH THE COMPRESSOR RUNNING, OR IT WILL EXPLODE.
If you need to charge with the engine running, you MUST charge with vapor (valve on the bottle is up) and it MUST go into the LOW-pressure port. Make double-sure that the red (high pressure) valve on the charging manifold is completely closed before starting.
Charging from little cans is a crapshoot as far as how much is going into the car. Some is bled off as you purge the charging hoses and valves, plus the volume stranded in the hoses is hard to guesstimate well. Each time you swap cans, you get to purge the lines again, and each time is a chance to push some air in with the refrigerant. Charge from the bottle, sitting on a refrigerant scale, with weights including tare figured only after the lines and charging manifold are evacuated and purged.
If you need to charge with the engine running, you MUST charge with vapor (valve on the bottle is up) and it MUST go into the LOW-pressure port. Make double-sure that the red (high pressure) valve on the charging manifold is completely closed before starting.
Charging from little cans is a crapshoot as far as how much is going into the car. Some is bled off as you purge the charging hoses and valves, plus the volume stranded in the hoses is hard to guesstimate well. Each time you swap cans, you get to purge the lines again, and each time is a chance to push some air in with the refrigerant. Charge from the bottle, sitting on a refrigerant scale, with weights including tare figured only after the lines and charging manifold are evacuated and purged.
05-23-2013, 07:49 PM
#7
Looks like we all do it a bit different.
On a fully evacuated system I'll open the taps on both high and low sides and then open the valve on my tank letting it all equalize. Once that's done I shut off the high side, start the car with both front and rear turned on full and fill using gas (not inverting the can/tank) through the low side port. While it is not a good idea to inject the fluid on the low side, you can sorta jiggle the can so a bit goes in.
You never want to have the high side open while the car is running/ac on. Exploding cans are not a fun thing to deal with.
On a fully evacuated system I'll open the taps on both high and low sides and then open the valve on my tank letting it all equalize. Once that's done I shut off the high side, start the car with both front and rear turned on full and fill using gas (not inverting the can/tank) through the low side port. While it is not a good idea to inject the fluid on the low side, you can sorta jiggle the can so a bit goes in.
You never want to have the high side open while the car is running/ac on. Exploding cans are not a fun thing to deal with.
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05-23-2013, 07:51 PM
#8
Nordschleife Master
If you want to charge with liquid as described above, engine is off and cold. You can charge that way to either port, but it's probably safer to put liquid into the high-side port. Then let the system settle for a few minutes while you disconnect the bottle and hoses, so the liquid will completely flash to vapor in the system before you even think of starting the engine and running the compressor. THE BOTTLE MUST NOT BE CONNECTED TO THE HIGH-SIDE PORT WITH THE COMPRESSOR RUNNING, OR IT WILL EXPLODE.
If you need to charge with the engine running, you MUST charge with vapor (valve on the bottle is up) and it MUST go into the LOW-pressure port. Make double-sure that the red (high pressure) valve on the charging manifold is completely closed before starting.
Charging from little cans is a crapshoot as far as how much is going into the car. Some is bled off as you purge the charging hoses and valves, plus the volume stranded in the hoses is hard to guesstimate well. Each time you swap cans, you get to purge the lines again, and each time is a chance to push some air in with the refrigerant. Charge from the bottle, sitting on a refrigerant scale, with weights including tare figured only after the lines and charging manifold are evacuated and purged.
If you need to charge with the engine running, you MUST charge with vapor (valve on the bottle is up) and it MUST go into the LOW-pressure port. Make double-sure that the red (high pressure) valve on the charging manifold is completely closed before starting.
Charging from little cans is a crapshoot as far as how much is going into the car. Some is bled off as you purge the charging hoses and valves, plus the volume stranded in the hoses is hard to guesstimate well. Each time you swap cans, you get to purge the lines again, and each time is a chance to push some air in with the refrigerant. Charge from the bottle, sitting on a refrigerant scale, with weights including tare figured only after the lines and charging manifold are evacuated and purged.
On these cars we know how sensitive things can be, and with the AC system I only fill to the 1050 gms after the system is evacuated. Last time I did this was three years ago and she's still ice cold.
05-23-2013, 07:56 PM
#9
Drifting
Thread Starter
How long should the system be evacuated for once it is opens to change a component. In my case I have changed the filter dryer and found that the compressor casing is leaking. I have the system under 100 psi pressure with nitrogen since replacing the filter dryer and all o-rings.
I will be replacing the compressor as soon as the new one gets here.
I will be replacing the compressor as soon as the new one gets here.
05-23-2013, 08:16 PM
#10
Team Owner
the longer the system is evacuated the more moisture will be removed from the lines.
2 to 4 hours if you have some time.
Then tighten the valve block shut off the vacuum pump and let the system sit for a while,
2 hours would be good to see if that system is holding vacuum IE not leaking.
Make sure that you replace both of the flex lines that come off the compressor these can be rebuilt at the hose shop, they will reuse your old hose ends,
Since they always leak its better to start with fresh compressor lines.
If no leaks, then you might consider following Dr Bobs method of adding to the high pressure side with the can inverted,
the filling process seems to go a bit faster this way,
obviously this is done with the engine off.
Put a rag over all of the hose connections when you remove the hose connections this will keep unwanted oil spray from soaking adjacent parts,
wear safety glasses
2 to 4 hours if you have some time.
Then tighten the valve block shut off the vacuum pump and let the system sit for a while,
2 hours would be good to see if that system is holding vacuum IE not leaking.
Make sure that you replace both of the flex lines that come off the compressor these can be rebuilt at the hose shop, they will reuse your old hose ends,
Since they always leak its better to start with fresh compressor lines.
If no leaks, then you might consider following Dr Bobs method of adding to the high pressure side with the can inverted,
the filling process seems to go a bit faster this way,
obviously this is done with the engine off.
Put a rag over all of the hose connections when you remove the hose connections this will keep unwanted oil spray from soaking adjacent parts,
wear safety glasses
05-23-2013, 10:42 PM
#11
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The correct level to evacuate your system is 500 microns. approx. 733,000 micron equals 1 atmosphere. Most people do not have micron gauges, so hard to say without a micron guage how long to evacuate.
If one leaves his/her system open to atmosphere (dependent on humidity level) water in the atmosphere will settle in the receiver/dryer (which has desiccant in it). That's why it's always good to replace the receiver/dryer when you open a system.
One can use a small vac pump it takes longer for evacuation. But say if use a 10 cfm oil less vac the evacuation may go quicker, all dependent on the moisture level of your system...
Per ARI 700 standard for refrigerants, 10 ppm per weight or less for R12 and R134a is acceptable for new or reclaimed refrigerants. Imagine putting a wet q-tip in a test tube, then attach by mechanical means to a vac pump, at 500 micron the q-tip would not have 1 ppm of water in the q-tip.
Water in a system at certain levels combined with refrigerant and heat (heat due to the process of compression) can and will cause acidity of the refrigerant. This will cause havoc on many components, seals, orings etc...
If one leaves his/her system open to atmosphere (dependent on humidity level) water in the atmosphere will settle in the receiver/dryer (which has desiccant in it). That's why it's always good to replace the receiver/dryer when you open a system.
One can use a small vac pump it takes longer for evacuation. But say if use a 10 cfm oil less vac the evacuation may go quicker, all dependent on the moisture level of your system...
Per ARI 700 standard for refrigerants, 10 ppm per weight or less for R12 and R134a is acceptable for new or reclaimed refrigerants. Imagine putting a wet q-tip in a test tube, then attach by mechanical means to a vac pump, at 500 micron the q-tip would not have 1 ppm of water in the q-tip.
Water in a system at certain levels combined with refrigerant and heat (heat due to the process of compression) can and will cause acidity of the refrigerant. This will cause havoc on many components, seals, orings etc...
05-23-2013, 11:51 PM
#12
Drifting
Thread Starter
Thanks for the info. I will let the vacuum pump run for 4-6 hrs. Before that I will pressure test the system with nitrogen to 200 psi and see if there are any other leaks. If all is good then I will evacuate it and recharge with R12.
I looked at the hoses and they look pretty good. The car only has 65000 miles on it and has been garaged all its life. Plus I don't have time to get hoses rebuilt or get new ones.
I looked at the hoses and they look pretty good. The car only has 65000 miles on it and has been garaged all its life. Plus I don't have time to get hoses rebuilt or get new ones.
05-23-2013, 11:56 PM
#13
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This is way easy - take it to Sean 8>)
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Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
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Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
05-24-2013, 01:51 AM
#15
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I'm of the thinking that, since I own the vacuum pump and there's no serious extra cost to running the 1/3 HP motor all night vs 45 mins or an hour as most shops do, I spring the extra pennies and let it do its thing all night long.
The pressure safety switch connects to the drier manifold at a schraeder-equipped fitting that lets you connect a vacuum pump. You then have the standard charging manifold connected to the normal ports and the gas cylinder. So you can evacuate the whole system including the charging manifold and hoses, no risk of air getting into the system since there's no connections or hoses to swap. No air means the system will be a LOT colder. Stupid stuff it might seem, but every little detail helps get the system colder.
The pressure safety switch connects to the drier manifold at a schraeder-equipped fitting that lets you connect a vacuum pump. You then have the standard charging manifold connected to the normal ports and the gas cylinder. So you can evacuate the whole system including the charging manifold and hoses, no risk of air getting into the system since there's no connections or hoses to swap. No air means the system will be a LOT colder. Stupid stuff it might seem, but every little detail helps get the system colder.