A/C refrigerant loss

[dockdoc]

My '02 had no AC the other day, and after jumping the low pressure switch I diagnosed low refrigerant as the culprit.

I ran a can of 134a with dye into the system, but couldn't find any obvious leaks under the UV light. There was nothing coming from any of the hoses or shrader valves, nothing at the condenser or the pump, and no water was coming out of the evap drain but I didn't see any dye around it either.

What's the next best move here? Was thinking I should vacuum it and see if it holds pressure, and if so then refill it? Let the AC run for a while longer (I gave it about 15-20 minutes) and then recheck?

Seems like the only other place to be leaking would be the evaporator which could be hard to diagnose. This is the first time it's lost refrigerant in the 25 years we've owned it, so I'm wondering if it's a super slow leak, and maybe a quick vacuum/recharge is all that's needed? Appreciate suggestions, I'm no AC expert!

 

[NashvilleTJ]

I've had leaks that were not immediately obvious with dye. Do you have a set of AC gauges?

If so, hook them up, connect a compressor, pressure it to 40 or 50 psi, and go to town with a sprayer of soapy water and look for bubbles.

If not, I'd definitely suggest picking up a set if you do your own AC work. You will use them over and over, as I have over the years. And, new tools are never a bad thing...

 

[KennethS]

Why vacuum it down just to recharge it? You’ll just end up back where you are right now. Check the pressure with gauges, add refrigerant if needed, run it for a week or so, then check again.

 

[macleanflood]

I'd grab an o-ring kit and replace all of them. Then see if holds vacuum for a couple of hours.

-Mac

 

[freedom_in_4low]

If it's a slow leak it could take weeks for the UV dye to show up and it could have been leaking for years to get to this point, until finally being short enough to actually show up in performance. Note the oil will take longer to get through than the refrigerant will.

When mine got low 2 years ago I topped it off (using gauges to charge to the correct pressures and temperature according to the conditions per the FSM) and it's still working fine. If it gets low again within 5 years I'll go through the system to fix it; if it takes longer than that, I'll probably top it off again.

 

[TheBoogieman]

I used this in my car 3 years ago. AC still works great.

 

[Link]

Mine was leaking from the evaporator. I charged it and then let it run on low fan for a bit. Stuck a sniffer up the condensate drain and it went crazy.

It’s not a hard job but takes some time. You don’t have to remove the steering wheel but do get 2 ratchet straps to help hold the dash back.

I use nitrogen for just pressure testing.

 

[Deputy Dodge]

Leaks may show up under vacuum, or pressure, or both, or neither. DO NOT PRESSURIZE WITH AIR! I would replace the drier and o rings and add the apropriate amout of oil, vacuum with a high quality machine, and charge by weight, not pressure.

 

[NashvilleTJ]

... DO NOT PRESSURIZE WITH AIR! ...

Why not? As long as you evacuate the system after doing so any additional moisture introduced would be removed. I've done it this way with no problems, and it identIfied leaks not revealed with dye. But, am I missing something?

 

[Deputy Dodge]

You can't boil off all the moisture added to the system with shop air. Especially from the desicant in the receiver. In fact the system should be sealed at all times so you dont get ambient air inside. Tape, foam ear plugs, whatever you can find to plug hoses as you're changing parts. Your mechanical gauge may show 29-29.9 inmg but it won't show you a micron level that a digital gauge will. The system could still have 23,000 microns of moisture at 29". I bought a $20 regulator from Amazon to connect to a nitrogen or argon tank so I can pressurize systems with clean, dry gas.

 

[NashvilleTJ]

You can't boil off all the moisture added to the system with shop air. Especially from the desicant in the receiver. In fact the system should be sealed at all times so you dont get ambient air inside. Tape, foam ear plugs, whatever you can find to plug hoses as you're changing parts. Your mechanical gauge may show 29-29.9 inmg but it won't show you a micron level that a digital gauge will. The system could still have 23,000 microns of moisture at 29". I bought a $20 regulator from Amazon to connect to a nitrogen or argon tank so I can pressurize systems with clean, dry gas.

Thanks for the info. Nitro and Argon is a great idea. I guess even with a water separator on the shop air enough moisture can get through to cause issues.

 

[Deputy Dodge]

It contaminates the oil just too, even just being open. If you want a deep dive into AC, this is a great place to look. If the link doesn't open, copy to a browser and it should work from there.

View: https://www.facebook.com/share/v/1CwpXeahac/

 

[freedom_in_4low]

It contaminates the oil just too, even just being open. If you want a deep dive into AC, this is a great place to look. If the link doesn't open, copy to a browser and it should work from there.

View: %5BURL%5Dhttps://www.facebook.com/share/v/1CwpXeahac/[/URL]

that link doesn't work for me (maybe because I don't have an active FB account), but I agree - the oil is hygroscopic and pulling it down to a vacuum won't completely remove the moisture it's absorbed.

 

[LJGreg]

My AC has been open for about a year due to a hole in my condenser. I have a new condenser and Drier / Accumulator coming and was planning to add the recommended oil, button it all up, leak test it, then give it to the shop to vacuum and refill. Good plan or is there something else I should be asking the shop to do?

 

[TJ4Jim]

My AC has been open for about a year due to a hole in my condenser. I have a new condenser and Drier / Accumulator coming and was planning to add the recommended oil, button it all up, leak test it, then give it to the shop to vacuum and refill. Good plan or is there something else I should be asking the shop to do?

Change out all your O rings and use the correct lube and I would also replace the Liquid Line w/ Orifice Tube assembly since it;s cheap insurance.