Recharging the A/C system after removing old refrigerant

[mecg]

Hey folks. Longtime member but it's been quite a while since I've been on Audizine.

So, my question today is how do I recharge a completely empty A/C system after suctioning out all the refrigerant out? The compressor won't engage to allow the new refrigerant to get sucked into the system. So, I need to know how I can get the compressor to run long enough to get the new stuff in the system? I can't seem to find an A/C relay to jump, as so many web sites suggest doing.

TIA!

[Audibot]

You really should have a professional do it.

That said... The refrigerant pressure sensor/switch will not allow the compressor to turn on if there is not sufficient refrigerant (pressure) in the system. If the system is at vacuum and holding, you should be able to buy a can or two of refrigerant and a manifold gauge set, and refill it manually. Remember the system fill is in grams.

1. Hook the gauges up to the high and low sides of the a/c system. You want all the valves closed. The gauges should read vacuum on both. If not, you have a leak still.
2. Weigh the can. Prob need a kitchen scale. If you can have it sit on the scale while filling it that'd be great. If not, periodically weigh it (but do not disconnect it).
3. Connect the can to the manifold. This will be the center hose. Remember--keep the valve shut.
4. Start the car and turn the a/c on LO.
5. Open the center valve and then the low pressure side valve and start filling. You should start seeing the gauges start increasing from vacuum to some positive pressure.
6. Once you have filled enough refrigerant, the switch will allow the compressor to kick on. At this point you will see a radical difference in pressure between the two sides.
7. Continue filling until you have entered the correct weight of refrigerant. At that point, your low side should be 2.5-3.5 bar and high side should be around 15-20 bar or so. This is ambient temperature dependent too, so may vary. Feel/measure the vent temperatures.
8. Close the fill valve and then remove the manifold gauges from the car. Keep in mind when disconnect the can from the gauge set, a small amount in the hose will leak out.
9. Enjoy cold air conditioning!

[mrg_B8TFSi]

That’s a really good step by step of a manual process of a recharge. But, before opening up any R134a cans. I would highly recommend to get yourself the gauge set and a vacuum pump.. you’ll need to look around for this stuff if you don’t already own or maybe auto parts store will rent? Anyway, make double, triple check on making sure you evacuated all condensable gases from the system using the yellow middle line on the gauge set, I’d pull on the system for at least 20min then do a quick 5 min leak test to see how well vacuum holds. If you’re good then you can proceed to the recharge procedure. But never open the high side valve during this and when disconnecting the low/ high sides burp the schrader valves to make sure they’re sealed.


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[RPMtech147]

You'll never properly charge the system with out at least a vacuum pump and a set of AC gauges. You can get within a couple ounces of dead on with the cans and watching your system pressure.

While you can just charge an empty system (when I say empty, I mean a system @ 0 bar, that's filled with air) by jamming a couple cans of 134 into it, running air through the system is terrible...it'll kill a new compressor in months; but with that being said, it should make enough pressure and actually cool the car. Sometimes you do have to clear the pressure faults from the climate unit, but if you jammed a can of refrigerant into the system, that should make enough pressure for it to turn on.

[ps2cho]

Its not "optional" to not vacuum the system. You MUST vacuum the system down for at MINIMUM 30mins, ideally 60minutes to boil off any water.

[mecg]

Thanks for all the great tips, guys. I used a vacuum pump to remove all the freon from the system and ran it a good 45 minutes. I also have a brand-new set of gauges to do all this with. I did everything exactly as Audibot described, except I did not hook up the high-pressure side (I watched a video where Scotty Kilmer said not to - it's not needed for a "simple" drain and refill and he says the high side valve often will leak after you disconnect from it).

At this point I'm thinking that I messed up somewhere, despite my being careful and deliberate while I did this procedure. With that, I'm going to start over and redo the whole thing. I'll post how it goes.

Thanks again!!

[Theiceman]

I think Scotty kilmer was your first mistake.

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[ps2cho]

Vacuum down for 10mins, close the gauge valves and let it sit for another 10mins, if it moves then you have a leak. If it maintains vacuum, then continue the vac for 45mins, close the valves and then recharge.

[mecg]

OK, so I started from scratch this morning and success!! I think I blew having the system still in a vacuum when I started putting freon back in the system the first time I did this a few days ago. Didn't mess that up today!!! And it came out pretty good, IMHO!! Air is blowing at 29.3°F now!!!

[ps2cho]

Nice job- did you. Charge by weight per the system capacity?

[Theiceman]

just curious as i dont know Ac that well .. wouldn't that completely freeze up the evaporator in humid climates ? if it is that at the vents you would think the evaporator surface is even colder, well below 32F. !

[DrGER]

Agree with @Theiceman. Spec for air temp just down stream of the evaporator (based on ambient air temp) is minimum 2C (35F) measured at -G263- (Address 08 MVB 035.1). Also check high side refrigerant pressure at -G395- (Address 08 MVB 001.4). --g

[mrg_B8TFSi]

Agree the air temp can’t be less than the freezing point of water at ambient conditions. I suspect that the thermometer is off. Your air temp coming out of the vents should be in the 40 to 45° F range with 75°F air temp. Now typically I’ll run the car while spraying the condenser with water to help cool it to simulate heat removal like wind flowing and do a final check with my gauges if you added the proper amount of refrigerant and H/L pressures read per the specs you’re good. But I’d recheck the vent temps with a probe thermometer like a turkey probe placed in the vent. < 32° F isn’t possible


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[RPMtech147]

Its not "optional" to not vacuum the system. You MUST vacuum the system down for at MINIMUM 30mins, ideally 60minutes to boil off any water.

lol..........

[ps2cho]

lol..........

Is there something you disagree with? Nothing I said is incorrect. Especially off the shelf harbor freight vac pumps that likely won't get down to 500 microns. You want to give it as much time as possible to boil off moisture and dust from when it was open to atmospheric pressure. Most should also replace any receiver/drier any time its open to air, but most don't...which is fine for a one-off, but if you're doing this 3-4x, the desiccant is risking getting full and you'll reduce the life of the compressor.

[Audibot]

Also running the car while vacuuming out the system can help by heating up the a/c system and driving off moisture.