I’m looking for a home mechanic setup to deliver nitrogen for pressure testing AC systems. It would be used only occasionally. What has worked for you? Thanks.
Nitrogen bottle and kit for pressure testing auto AC systems
- Thread starter Snagglefoot
- Start date
I cobbled this up 20+ years ago using fittings cut off old accumulators, gauges from an oxygen tank and whatever else I had. I Used R12 fittings but found a screw on adapter to connect the R12 fitting to an r134 hose if needed.
This is in my garage now.
I sure do miss ac work.
This is in my garage now.
I sure do miss ac work.
Attachments
Oh. The 2 gauges on top allow me to adjust the pressure as to not blow up parts. I test @ no more than 200 psi. An evaporator can't take much over 200 psi.The 3Rd gauge on the side is just a way to drain the pressure when I'm done pressure testing.
JHZR2
Staff member
Do you have N2 in a bottle? Maybe more specifically, bone dry N2?
If so, just play the fitting adapter game to get to the acme threads for R-12 or 134a.
Im not sure how wet fire extinguisher co2 is, but that’s one Ive been considering. Run a proper regulator from the extinguisher to manage pressure and fill a system to check for leaks.
Persomally I use HC refrigerant blends that are known to be dry. This way I can sniff for them with a flammable gas detector.
I presently have AC gages but nothing in the way of a N2 bottle or regulator. Yes, I have HC refrigerant in the system right now as well, and use dye, but may have a minute leak somewhere. So far it’s holding. The system held during the vacuum session earlier this year.
I use co2 out of a 150 cubic foot Inert Gas Cylinder, Old Victor regulator, And a co2 detector mostly for suspected Evaporator Core leaks.
Gas Detection equipment is unreliable in well ventilated areas in my opinion.
In my experience, I've seen nitrogen used (preferred), but also shop air (dried), shop air (non-dried), propane, CO2, and whatever other pressurized gas was around that was easy to get hands on. EPA even allows low pressure charge with proper gas for leak detection.
I personally like nitrogen because it's dual purpose - A/C and tires.
If you already have shop air and a dryer, I would just use that and avoid the expense of something else. Just run the vacuum a little longer and ensure that after you cut off the machine it holds the desired level of vacuum for the proper time.
And before everyone shoots this down because of acid formation, dry shop air is pretty dry compared to atmospheric. If it good enough to paint with, it should be okay.
One caveat: If it's a newer system (1234) I personally would only use nitrogen. Same with 410 for home (and the newer 35 or 45 replacments). These systems are not as moisture tolerant IME and depending on your dryer may not perform up to spec.
It's obviously up to you and how much money you want to spend, and how often you use it. A bottle of nitrogen and a regulator are not very expensive, but it will cost more than shop air if you already have a compressor and a dryer.
I personally like nitrogen because it's dual purpose - A/C and tires.
If you already have shop air and a dryer, I would just use that and avoid the expense of something else. Just run the vacuum a little longer and ensure that after you cut off the machine it holds the desired level of vacuum for the proper time.
And before everyone shoots this down because of acid formation, dry shop air is pretty dry compared to atmospheric. If it good enough to paint with, it should be okay.
One caveat: If it's a newer system (1234) I personally would only use nitrogen. Same with 410 for home (and the newer 35 or 45 replacments). These systems are not as moisture tolerant IME and depending on your dryer may not perform up to spec.
It's obviously up to you and how much money you want to spend, and how often you use it. A bottle of nitrogen and a regulator are not very expensive, but it will cost more than shop air if you already have a compressor and a dryer.
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As I recall there's an adaptor you can get to connect the nitrogen regulator to the yellow hose of your manifold gauge set.
I just use welding argon since I already have the bottle. Just needed a high pressure regulator.
JHZR2
Staff member
If a gas detector isn’t reliable, now is a co2 detector reliable?
Do you buy specific co2? I’m curious how dry extinguisher grade CO2 is.
Evap is in a closed environment like the heater box. Only place it would be reliable since CO2 would be trapped inside it or at least detectable coming out of the heater box. Testing lines, compressors or a condenser is too much of a ventilated area for a sniffer to be reliable, that's where dyes are the best.
My argon detector is full it up and see if it still has pressure the next day. If not, then it's time for some soapy water.
Required to pressure test also but few do it.
That only catches big leaks. Vacuum only gets you to 14.7 psi external pressure trying to get in (around sea level). In an automobile with R134a, the system is charged to at least 70 or 80 lbs static pressure (depending on outside temperature) and the high side will go anywhere from 200 to 300 PSI in operation.
I just use compressed air. I have a home made adapter that I made specifically for this purpose that I can connect to an air compressor hose..
I hope you have a way to remove condensation from your tank and lines.
Air compressors normally have drains, yes.
