(In Minecraft, of course. And in Mexico.)

A friend tried to recharge his auto air conditioner *. Apparently he damaged the valve on the low-pressure line, as when he removed the recharging bottle the valve leaked a lot.
If he replaced the schrader valve, would the recharging bottle have enough oil and coolant to properly refill the system?


*1998 dodge 1500 truck if it matters.

He's going to need a vacuum pump to evacuate the system before recharging.

Any particular reason? There's still some oil in the system as it wasn't running as the coolant ran out. And there's no reason for air to leak into the system.

He's trying to do it as cheaply as possible.

If you remove the core from the Schrader valve to replace it, air will enter the system.


Eta:  Maybe not enough to matter.  It may be a little less efficient.  I'm not sure how a little air would affect it.

To your original question, use as many cans as it takes.

Some cans have oil, and some do not.  If the system didn't lose any, I wouldn't add any.

If no oil came out [and he'd know it] then it doesn't need an oil charge. Air is bad in a closed A/C system. Doing a proper evac and drawn down of the system, hell, you may as well fix the leak, draw it down and recharge it properly with the correct amount of oil and refrigerant.

A cheap procedure will give cheap results. The original leak needs to be fixed, both schraders replaced, vacuum evacuation for 15+ minutes, leak test, then recharge to manufacturer specs.

If he just wants to vent the system to atmosphere and replace the valve and charge it, chances are it won't cool to anywhere near its full potential. I'm going to guess it was probably completely empty the first time he tried to charge it?

I think that system holds 1.5 pounds, iirc.

So he won't wreck the system by recharging it this way?

It won’t cool good because air in the system is a non-condensable gas the system pressures will run high, you need to vacuum it before charging to remove moisture and air that entered the system when you opened it to atmosphere when changing the Schraeder valves.

I'm not sure about the mexican minecraft stores, but here in the real world, most vehicles I've had to DIY the AC on took 2 cans or less of the cool juice from autozone.  Thats like $24.  And the vehicle says how much refrigerant it is supposed to have.  I dont know how to accurately add some to a partially filled system and be insured that you have added the correct amount.  You would need to start from a known number.  The only known number that you can easily get to is zero.

Fix the issue, pull a vacuum, add the correct amount of refrigerant.

Yes you can use the cans. To do so after being vented to atmosphere will take a long time. It will make the system work harder if it is not properly filled.
Using gauges and a vacuum pump can also tell you if you have an additional leak. Also if your system is operating properly.
I also belive that vehicle uses an orifice tube. These have little filters in them that can get clogged. If you open the system. That should be replaced. If you examine the filter and see metal in it. Stop. Replace it all. You will thank me later.

The system is designed to be filled from a vacuum. I've never tried pumping goo juice from vatozone into system that's at atmospheric pressure but I'd imagine that you'd struggle to get the proper amount of freon in there and your pressures will be way off, resulting in shitty performance and potential future damage.

A cheap vacuum pump and gauge set is like $150. It's well worth the money. I always replace shrader valves, every time. They always leak. Complete kit for that truck from 4 seasons is probably less than $200. For $350 you'd have a new compressor, accumulator, hoses. You'll know how much oils in it, and it will blow cold for another decade or two.

Or keep pumping $25 cans of crap in there until it explodes.

Got 'er fixed!

I He pulled the dust cap and some coolant started leaking. Hooray, sez I; he; the system still has pressure and has kept atmosphere out. So I  he probed it a little with a small Phillips screwdriver and the hissing stopped!

I  he continued with a can of coolant and now the AC works just fine. It's 98 F now, topping off at 106. Nice and cool inside the cab!

THANKS to all for your help!

You don't know much about refrigeration if you think a system  cannot be easily charged  when under pressure.   I will admit that  measuring charge into  an evacuated system  is the best way,  but if the system still has a partial charge,   systems  can be charged from a partial remaining charge if you can  establish  some  conditions that are relevant.   In other words  operating condtions  thatr would be realistic,  and  factory  pressure readings  re:   wet/ dry bulb and so on.    Frankly, the singular most important  thing you can do is to insure that the compressor  sees  adequate superheat so that it does not  slug.   Probably second is to insure that it does not see excessive head from overcharge, and of course that means  subcooling.

I see NO  need to  evacuate a system that for certain is still under pressure,  and one that  you feel  has not been subjected to  a vacuum.   Most any system with a low pressure cutout  and that has not seen  winter low temps  will meet that,  with a bit of common sense.  

The biggest issue  with automotive systems is the wide  operating conditions they face.

Also you can easily  (usually) replace   Schrader valves with the proper tool.  The first one I bought, for  common  1/4" flare service taps,  was about 1982,  and I still have it.   Since then, I've acquired several others.

You can easily  remove most of a charge without  a recovery  system  by simply using  a recovery tank which you've made sure is  "clean"  and evacuated, and then left in the freezer overnight.  All you need do is get the system down into the vapor only pressure range,  and low enough that you can deal with it, say  15--20PSI.  Then you can  change Schraders WITHOUT  the special tool, and simply  use your finger to hold pressure, just as iff you were doing so on a tire.

Truth be told, as long as the system still has some pressure, if you were to quickly replace a schrader valve core, almost no air would get in the lines.  It's a tiny hole, and the refrigerant won't just flow out, and air won't just flow in.

Woah, sorry about your mom's knees, bro.

You're right. I don't know much about refrigeration. I have successfully repaired hundreds of vehicle air-conditioning systems, though. I'm not an engineer. Maybe others can figure out how to change a system to 1.68 lbs when they have lost some refrigerant but I am not that smart.

Every manual I have every read tells you to evacuate the system and charge it to a specified level, sometimes dependant on elevation. Occasionally, they will tell you to add x amount and check the temp of the lines but they always give you a starting point in pounds. I usually just do what the book says. This not only ensures you are starting from scratch and allows you to check for leaks; it removes moisture, as refrigerant oils are hydroscopic.

Why was OP's "friend" was messing with his system in the first place. Judging by the age of the vehicle and willingness to jam a can of AutoZone cool juice in there, he's probably been dicking with it for a while. I stand by my recommendation of replacing the hoses, descant, and Schrader valves at a minimum.

I wish my Roadrunner came with a 440. I jammed a 440 and a 727 in my '70 Duster when I was in highschool though. 20 something years later, I can finally afford to paint it.

Attached File

If the 1998 truck doesn't have a fairly new compressor in it, then it's probably leaking from the the compressor clutch shaft seal. Trying to pull a spec vacuum on a high mileage is wasted time.