Orifice tubes

Since we're talking about orifice tubes and pressures I thought I'd post here, (sorry @Scooterwrench if it isn't proper. Let me know if you want me to go away) I just received my new R134a Low Pressure Cycling Switch (thanks @L31MaxExpress for that) and connector, in case I have a problem adjusting the 36 year old one. The switch shows rated, open @ <21 PSI and closed @ >42 PSI AND has the adjusting screw between the electrical connector blades, you can see it in the picture. The funny thing is, the white threaded fitting that goes on the Accumulator/line is made out of plastic maybe that's a good thing...

Supercharged111 said:

Wouldn't it make sense to blow the solvent back toward the orifice tube?

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Yes. I would reverse-flush first. Less chance of pushing debris into the evaporator.

Consider putting a coffee-filter over the outlet, secured to the pipe. You can then (maybe) check the filter for actual debris blown out by the flush. The flush pressure may blow the filter off the pipe, or rip it, or otherwise screw-up your finding debris...but you can try.

Supercharged111 said:

to be clear, downstream of the orifice tube doesn't require component replacement for debris, just a flush?

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LOOK at the orifice tube screens when it comes out. If it's relatively clean...a back-flush of all re-used components and you're probably good.

If it's filthy (but intact) you'd better flush all the re-used components both directions, and maybe consider replacing the evaporator. Of course you're replacing the compressor along with the condenser if the orifice tube has debris. (Always replace the accumulator/receiver/dryer whenever the system is opened-up.)

If the screens are ripped, you need new everything.

The aftermarket has filters for the suction side of the compressor. Not a bad idea if there's any possibility of debris in the system.

PlayingWithTBI said:

Since we're talking about orifice tubes and pressures I thought I'd post here, (sorry @Scooterwrench if it isn't proper. Let me know if you want me to go away) I just received my new R134a Low Pressure Cycling Switch (thanks @L31MaxExpress for that) and connector, in case I have a problem adjusting the 36 year old one. The switch shows rated, open @ <21 PSI and closed @ >42 PSI AND has the adjusting screw between the electrical connector blades, you can see it in the picture. The funny thing is, the white threaded fitting that goes on the Accumulator/line is made out of plastic maybe that's a good thing...

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All good man,
The factory switches have plastic sockets,you shouldn't have an issue as long as you don't get crazy with the wrench. I tighten 'em up by hand.

Scooterwrench said:

All good man,

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Thanks! I decided to start my own self-deprecating thread anyway.

Alright,got my redneck freon recovery system all tuned up and got the .057 and .047 orifice tubes. Tomorrow morning I'll catch the freon and change out the orifice tube and charge it back up. When I changed out the compressor I started to pull the whole grille to change the O-tube and discovered all I need to pull is the right parking light.

Scooterwrench said:

got my redneck freon recovery system all tuned up

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How old is that motor and compressor? Did you steal them from the Smithsonian?

FYI, looks like your gauges are off a little - a perfect vacuum is just under 29" but, it looks good to me

PlayingWithTBI said:

How old is that motor and compressor? Did you steal them from the Smithsonian?

FYI, looks like your gauges are off a little - a perfect vacuum is just under 29" but, it looks good to me

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I don't know how old that motor is. It's a 1/4hp GE with babbit bearings,runs silent. I'm guessing 1950's? The A/C compressor came off a '77 Ford P/U and I just rebuilt it with new rings,gaskets and redesigned crank seal more suitable for vacuum.
I zeroed that gauge twice because I thought the same thing. I bought those gauges to balance the carbs on a Harley that had twin S&S's on it. Probably not 30 in hg but both gauges gave me the same reading. I've got another combination fuel pressure/vacuum gauge and my old manifold set I'll compare those.

PlayingWithTBI said:

...the high side showed ~275 PSI while the low side actually showed a vacuum.

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What I find interesting is the valves in the compressor managed to retain a seal long enough for you to actually measure a significant pressure differential.

Since it appears the compressor pitched crap into the high side (a plugged OT) I would wonder if the compressor valves would have sealing problems, either from retained debris or the effects of having passed the debris through them.

Live, observe and learn.

Scooterwrench said:

Alright,got my redneck freon recovery system all tuned up

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Nice, that's something I've wanted to do.

Have you got a pressure relief valve in there somewhere?

I thought about using the compressor that's actually on the vehicle (draw liquid out the high side via the service fitting) but figured it might be quite hot(!), didn't want to lose the miscible oil, and considered that other problems might accrue

1998_K1500_Sub said:

What I find interesting is the valves in the compressor managed to retain a seal long enough for you to actually measure a significant pressure differential.

Since it appears the compressor pitched crap into the high side (a plugged OT) I would wonder if the compressor valves would have sealing problems, either from retained debris or the effects of having passed the debris through them.

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That was my stupid mistake - see here.
www.gmt400.com/threads/stupid-mistakes-you-make-on-a-c-systems.68661/