Charging new AC system

Evacuation, you must remove all the non-condensables from the system and that means pulling a vacuum down to 500 microns. Without the proper tools and training it is best left to the professionals.

Steve

Besides what TSolo said, what freon are you planing on using? Yorks were set up for R-12, and most A/C gauges sold nowadays are threaded for r-134a fittings- which are made different on purpose. The York has a separate oil sump like a single-cylinder motorcycle engine and the lubricating oils used with the two freons are different as well- and incompatible. Nothing wrong with using R-12 except the outrageous cost.

This is a new compressor, will accept either Freon. Bummed out as I am, I guess I'll let somebody mess with my car. Man I don't like that.

quote:

This is a new compressor, will accept either Freon.

As such it MAY come pre-filled with the needed oil fill. And if like current Sanden compressors, that means it will be filled with a r-134a compatible oil. if using r-12 you need to drain the factory 134-a oil and fill with correct r-12 oil.

I am a do-it -yourselfer. Ac issues can be a real challenge. Yet, you can save serious money doing it yourself and acquire some neat gadgets in the process. As a starter you will need a good set of gauges and ideally, a two stage vacuum pump.

Shopping around it looks like for about $150.00 you can get a whole system. Pump, hoses gauges. That's a little too temping to not try it. If the instructions are good, and as long as you get the low side and high side straight what's the worst that can happen? Overfilling?

quote:

what's the worst that can happen?

Set the Stage -

-- car running, AC on
-- gauge set hoses connected
-- 12 ounce freon can connected to yellow hose
-- accidentally open high side valve into the
12 ounce can
-- 12 ounce can explodes when hit with
the 250-300 psi of the AC system

Not likely, but you asked.

Ray

Ron (accobra) is in the A/C business, he'll be a good resource, hopefully he'll contribute to your topic.

I've done a lot of A/C filling and refurb in my life.

To fill an A/C system from scratch you gotta draw it down to a very low vacuum, after it is drawn down (which only takes a few minutes) keep the vacuum pump on it for a couple of hours to boil-off any moisture, then close the valve between the vacuum pump and A/C system, and observe the A/C system pressure (vacuum) for 2 to 24 hours. There should be an accurate vacuum gauge on the system, as part of your refrigeration manifold, which is also hooked to the bottle you plan to fill from. You should be able to observe that the vacuum does not decrease at all over the observation period, indicating there are no air leaks into the system. If the vacuum does drop-off you have some leaks to chase down before you can fill. Repeat this step as often as necessary.

You should have an idea how much refrigerant the system holds, in terms of weight. Its gonna be more than 2 pounds but less than 4 pounds. I can't remember the exact weight for the Pantera, perhaps somebody can help with that info. So you place your refrigerant bottle on a scale, and do an initial fill based on weight while there is still a vacuum on the system. Close the valves and bottle the system up again.

Start the engine, and let it idle until the coolant is at normal operating temp. Then set the engine to idle at 1500 rpm. This is the engine speed (rpm) at which automobiles are operated while filling their A/C systems. This speed is important because it impacts the pressures on the suction and discharge of the A/C compressor.

Place a thermometer in one of the A/C outlets on the dashboard, to monitor the temperature of the cooled air. Roll the windows down and/or open the doors. Set the fan at high speed, set the temp control at maximum cold, and set the air vents for normal operation (as opposed to max A/C or recirculation of air). The A/C compressor clutch should be engaged and the A/C system should be blowing cold air from the vents.

Using the A/C manifold, admit some gas from the refrigerant bottle into the suction of the pump (while the engine is running, idling at 1500 rpm). The system pressures shall spike a bit. Close the manifold valve and allow the system pressures to stabilize. Stabilization will take a minute or two. The pressures should stabilize at a somewhat higher reading, and the temp of the air blowing out of the dash vent should be a bit colder. This indicates the system is low on gas.

You want to repeat this procedure until you reach a point where admitting additional gas does not increase the system pressures or make the air blowing out the dash vent colder. At that point the system is filled, operating at equilibrium, and the receiver tank is beginning to fill with liquid Freon (the excess Freon is condensing). You can often determine the level of Freon in the receiver tank by observing the "frost level" on the outside of the tank. I like to fill the system until the liquid level (frost level) in the receiver tank is about 50%.

The suction pressure of the compressor should be 10 to 20 psi at equilibrium. The discharge pressure and the air temperature shall be dependent upon the ambient air temp and humidity. You hope the discharge air temp will be in the 40 degree F range, and the compressor discharge pressure is between 180 and 240 psi. Old receiver/dryers (plugged with debris), bad expansion valves, or hot days will cause the discharge pressure to run higher. If the compressor discharge pressure reaches 300 psi before the system reaches equilibrium you should shut down the fill procedure and figure out what is wrong.

Regarding using R12 verses using R134a, R12 is a more benign gas. R12 is compatible with mineral oil based compressor oil and typical rubber elastomers. R134a is not. R134a is more corrosive, and is a smaller molecule that leaks more easily. Equipment compatible with 134a shall also be compatible with R12 ... but the opposite is not true. Equipment compatible with R12 is not necessarily compatible with R134a. For instance hoses ... R134a will leak right out between the molecules of the oem rubber A/C system hoses, and it will attack them and turn them into "goo" at the same time. R134a hoses are normally lined with Teflon. The same is true for the material used for the fitting O-rings and the seals and valves within the compressor. Viton, which is used for R12 is not compatible with R134a. The compressor oil is also different for R134a.

If you decide to use R134a, the system will perform better if the expansion valve is replaced with a valve designed for R134a.

Scott Bell converted his Pantera to R134a years ago, he shall be a good resource in that regard.

Okay, thanks. That info along with a few videos, and I'm going to give it a go.

Vinh's A/C has been out of service for years.

We are going to replace the York pump with a used Sanden that is plumbed with R12 nipples and flare fittings. We plan on refilling with R12.

Would someone please elaborate on flushing solvents and methods?

How about flushing and refilling the sumps in the compressors?

And another situation: How would one go about recharging a currently operating system opened for maintenance reasons? For example, I want to replace an iffy looking hose in my car at the receiver/dryer. I cracked the fitting open with a wrench and she has plenty of pressure and the gas seems to be carrying lots of oil too. I quickly retightened the fitting.

And also, if the compressors have sumps to carry their own oil, what are the small pressurized cans of R12 oil fed in through the charging manifolds supposed to do? There are no moving parts elsewhere in the system that require oil, are there?

Re-charging an open system is done exactly as George describes above. The system should be pulled down with a vacuum pump.

This is pretty helpful.

https://www.youtube.com/watch?v=lglPJuBXVeE

It sounds like the area of expertise needed is understanding pressures. I don't think it's all that important for a one time, one car operation.

Does anybody know what the OEM freon capacity is?

quote:

Does anybody know what the OEM freon capacity is?

I've heard of owners using from 2 to 3 1/2 pounds.


big help, huh?

Watch your drier view port for bubbles and see if your H/L pressures appear within range for your ambient temperature.

Of course, you'll also have a thermometer lodged in one of the dash vents to tell you how you're doing.

quote:

Originally posted by larryw:

Would someone please elaborate on flushing solvents and methods?

All I've ever done was to remove one "component" of the system at a time, flush it out with an aerosol spray can of solvent that air dries leaving no residue (like contact cleaner), and then blow it out with compressed air. Most of the "gunk" in the system will be trapped in the receiver on the outlet of the condenser. It usually has a filter of some sort in it, and a pack of drying agent to absorb water. That's why the receiver should be replaced when ever the system is opened up. I've seen expansion valves with crud lodged in their inlet too. Some expansion valves have screens at the inlet.

quote:

Originally posted by larryw:

How about flushing and refilling the sumps in the compressors?

If the oil looks clean just top it off with the same type of oil. If the oil is dirty flip the compressor over and let it gravity drain, then refill with fresh oil.

quote:

Originally posted by larryw:

And another situation: How would one go about recharging a currently operating system opened for maintenance reasons? For example, I want to replace an iffy looking hose in my car at the receiver/dryer. I cracked the fitting open with a wrench and she has plenty of pressure and the gas seems to be carrying lots of oil too. I quickly retightened the fitting.

To replace any part of the system you have to bleed off the Freon. Of course, in these days you're supposed to capture the Freon rather than bleeding it to atmosphere. That can be accomplished with an empty tank and the vacuum pump. You'll have no way of knowing how much of the compressor oil is lost during your bleeding procedure. After you replace the part you'll have to measure the amount of oil in the compressor with a "wire dipstick" and top off what is lost, or drain the compressor and refill with the proper amount. Afterwards draw the system down and perform the procedure I've already described. You see, Freon has an affinity for moisture, it will absorb moisture from the air. So you have to draw the system down to a very high vacuum for a couple of hours to boil off any moisture that made its way into the system while it was opened to atmosphere (water boils at room temp under a vacuum).

quote:

Originally posted by larryw:

And also, if the compressors have sumps to carry their own oil, what are the small pressurized cans of R12 oil fed in through the charging manifolds supposed to do? There are no moving parts elsewhere in the system that require oil, are there?

As you found out when you cracked the fitting on your system the compressor sumps are not isolated from the system. You're right, only the compressor needs the oil, but the oil is carried by the Freon throughout the system when the system is in operation. It is assumed that as Freon leaks from the system a small amount of oil is lost too, you've probably noticed the place where Freon is leaking is usually covered in oil. So the small cans of Freon have a small amount of oil in them to replenish the oil that is assumed to have been lost. The replacement oil will circulate through the system, and the majority will find its way to the compressor and stay there.

When I did my car I installed a high low switch in the high pressure line next to compressor . All new cars have this feature. Before I had installed switch at high RPMS it blew Freon all over my engine bay. also replace all hoses compressor and expansion valve to r134

Thanks George. Got it.

Bill, Since my car has been fitted with an R12 rotary pump and the charging equipment I have access to is also all R12 stuff, I'm going to stick with that.
I have over a dozen NOS cans of freon on hand, and it's still easy to find on Ebay. Summit still sells bottles of the proper oil for the R12 compressors too.
With 40 year old hoses my system has held it's charge for at least five years now, still blows cold. Even the iffy hose I described earlier doesn't actually leak (yet).
I did install a binary switch at the receiver dryer, it's wired in series with the compressor relay pilot circuit. If the system is over or under proper operating pressures the compressor won't engage.
Next time I empty the system I'm going to swap the binary switch for a trinary switch and use the third wire to control the condensor fan relay.