Releasing pressure from A/C system?

[71CHEVYSHORTBED402]

I have the need to remove the lines connected on back of the A/C compressor. Technically, I just want to see the bolt. The A/C is hooked up, though it's not operable. I can't speak for any Freon or system pressure. If I sound ignorant, it's because I am.

Anyway, safe to assume you release any pressure first? If so, how is that accomplished? Perhaps what's pictured is exactly for that, a pressure release valve?

Thank you

[davepl]

If you think there's refrigerant in the system, your best bet would be to take it somewhere (pretty much any shop that can service AC) and get it removed (vacuumed out). They actually save it, I think, and you get a credit against what they removed when you go to have it recharged. At least that's the way it works around here (Seattle).

You could just crack a line and let it all escape, but you'd be wasting some money and I suppose it's not a great idea to dump CFCs into the air without reason.

Odds are, however, that the refrigerant has been gone for a long time...

Backing up a little, though, why do you need to release it? Even if you're pulling the motor you can normally leave it all connected and just place it off to the side.

[B. W.]

Yes, that valve is used to recover refrigerant & re-charge the system. (there are two, one on the high pressure side & one on the low) You may not need to disconnect the hoses though. If you just want to remove the compressor from the bracket you can unbolt it & move it to the side with the hoses/lines attached. When I do engine swaps this is the way I do it so I don't have to recover / re-charge.

[engineer_gregh]

That is the high pressure side. The valve on the POA valve is the low pressure side. You could press the valve on the low pressure side to see if there is any freon left in the system. Much like releasing air from a tire, make sense?

[71CHEVYSHORTBED402]

Originally Posted by davepl

If you think there's refrigerant in the system, your best bet would be to take it somewhere (pretty much any shop that can service AC) and get it removed (vacuumed out). They actually save it, I think, and you get a credit against what they removed when you go to have it recharged. At least that's the way it works around here (Seattle).

You could just crack a line and let it all escape, but you'd be wasting some money and I suppose it's not a great idea to dump CFCs into the air without reason.

Odds are, however, that the refrigerant has been gone for a long time...

Backing up a little, though, why do you need to release it? Even if you're pulling the motor you can normally leave it all connected and just place it off to the side.

It's on my driver truck. I have no intention to ever run the A/C system, at least not for a LONG while. Even if I did, I'd probably switch to 134A.

Honestly, ha, I want to see what that bolt is, and any other washers or rings with it. The bolt is missing from the truck I'm rebuilding, so I know just where to get one.

[engineer_gregh]

The single bolt that attaches the line to the compressor can either be SAE or Metric, both compressors are available new or remanufactured. The threads on the SAE are fine thread, not sure of the size. No washer on my 402. I have mine loose now, if you would like a picture let me know.

[71CHEVYSHORTBED402]

Am I on the right track here? See pics., thank you:

[B. W.]

You are correct, that is the low pressure port. Both valves are used to recover & re-charge. When the system is off, the pressure is equalized between the high & low sides so it doesn't matter which one you use to release pressure.

[71CHEVYSHORTBED402]

Originally Posted by B. W.

You are correct, that is the low pressure port. Both valves are used to recover & re-charge. When the system is off, the pressure is equalized between the high & low sides so it doesn't matter which one you use to release pressure.

Thank you for the confirmation etc. B.W., and others for info.

[engineer_gregh]

The truck looks to have all its original a/c parts in place with the exception of the compressor. All of the screws and brackets are present, even the ones on the high pressure hose, and evaporator core. Great picture of how things should look when original. I don't know why the a/c is not working but its definitely worth repairing. Thanks for posting the pictures.

[71CHEVYSHORTBED402]

Originally Posted by engineer_gregh

The truck looks to have all its original a/c parts in place with the exception of the compressor. All of the screws and brackets are present, even the ones on the high pressure hose, and evaporator core. Great picture of how things should look when original. I don't know why the a/c is not working but its definitely worth repairing. Thanks for posting the pictures.

It was nice to have the "sample" for certainty. I pulled the A/C off my other in 1993, and wasn't paying attention. Turns out I had all the parts less some bolts. Even found the correct stud for the brace support on the exhaust manifold. It was missing off the "sample" truck. They used a bolt and spacer instead. Other than that it's all there.

[71CHEVYSHORTBED402]

I pulled the bolt. It's 3/8-24 x 1.3/8. Engineer, there was a washer and lock washer, which is correct per the assembly manual, page 517. The washer has a 3/4" diameter.

This bolt looks original to me, so I decided my 71 project needs it more than the 72 HA!. It's not all bad for the 72. Getting ready to install the newish parts I pulled off the 71, starter, battery, cables, etc. Besides, I can actually drive the 72.

[engineer_gregh]

My bolt was missing and F.A.Abenny was nice enough to send me this one.

[71CHEVYSHORTBED402]

Not to hijack this thread , does anyone know what this is called, perhaps a brief description of operation? See image, thank you

[71CHEVYSHORTBED402]

Originally Posted by engineer_gregh

My bolt was missing and F.A.Abenny was nice enough to send me this one.

Ha ha, very cool.

Turns out I got the other bolt after all. It's exact. I have a stash of hardware I've kept so long, but they looked "right", so I never got rid of them. That's twice it's paid off for this A/C, and I couldn't have asked for a better two.

I should have mentioned earlier, not a puff released when I depressurized.

[RichardJ]

>>, not a puff released when I depressurized. <<

Not exactly sure what you really did, but that is a good way to get an eyeball full of refrigerant and oil.
Generally you would connect the gauges, which would show how much pressure is in there. Then if you are inclined to just vent it to the atmosphere, you can do it in a controlled manner and you can collect any oil that comes out with the refrigerant.

[engineer_gregh]

That's the original expansion valve. It can be rebuilt. Don't throw it away as it's much better than what's available now and that style is no longer made.

[71CHEVYSHORTBED402]

Originally Posted by RichardJ

>>, not a puff released when I depressurized. <<

Not exactly sure what you really did, but that is a good way to get an eyeball full of refrigerant and oil.
Generally you would connect the gauges, which would show how much pressure is in there. Then if you are inclined to just vent it to the atmosphere, you can do it in a controlled manner and you can collect any oil that comes out with the refrigerant.

Yeah, I probably shouldn't have taken a chance DON'T TRY THIS AT HOME KIDS. I did suspect there was a lot of loss beforehand, and was careful. I took a tire gauge to the POA valve and nothing. Then I pulled the bolt off the lines to the compressor & nothing. Might be worth mentioning, that bolt goes on TIGHT. At least that's how I found it. When I put it back on, yeah, wrenched it on but good. I'm new at this, but that's what it seemed to want.

Originally Posted by engineer_gregh

That's the original expansion valve. It can be rebuilt. Don't throw it away as it's much better than what's available now and that style is no longer made.

Thanks engineer, appreciate everything. Based on some notes I took from beforehand, that was my impression.

No plans to revise the AC in this 72. Nice to have the parts though. It's the 71 that gets the makeover, to 134A. New condenser, POA valve, hoses, and a rebuilt compressor.

I believe, the existing expansion valve works with 134A?....................I gather the evaporator works with R12 & 134A. But if I recall, (been 25 years), my evap. was exposed to the elements, for maybe a month. That and it's obviously empty, less some oil perhaps........ Not sure the affect. Probably just as well to buy another. I hear they mount the same.

So yeah, ha!, somewhat original appearance, but not..............On topic, I have one can of R12. $2.95 price tag, from Grand Auto.