Help! A/C techs!

[HOGDADDY]

This will work. I am going to use one soon too.
There are 2 different kits depending on the threads.

https://coldhose.com/collections/swi...35532366151840

[hatzie]

Originally Posted by HOGDADDY

This will work. I am going to use one soon too.
There are 2 different kits depending on the threads.

https://coldhose.com/collections/swi...35532366151840

You can get binary HPCO/LPCO switches to replace the LPCO switch on the accumulator that are direct plug and play replacements. I'd use one of those if you're installing a binary switch. The fact that your AC guy didn't immediately suggest this makes him more than slightly suspect IMHO.

Folks are frightened of AC work. It's not oogie boogie. If you have any mechanical aptitude and some patience you can do your own AC work on an already empty system.

Download the 1973 GM CK light truck service manual and read the AC section. It's a fairly extensive overview theory of operation service methods etc. 73 used a TXV system rather than an orifice valve but the broad strokes are the same.
The GM service training group AC textbook is scanned and downloadable amongst the 73-91 manuals as well.

You can usually rent a vacuum pump and R134a manifold gauges from The Borg Collective stores. O'Riley, AutoZone, etc. Refrigerant and oil is still reasonably available as long as you aren't trying to by R12.

If you're retrofitting the refrigerant there are several things that need to be on your list so your system hangs together.
The condenser and evaporator and hardlines need to have all the old R12 mineral oil and bugs and crud flushed out. R12 mineral oil is not compatible with R134a so it won't flow around the system with your refrigerand and it'll impede heat transfer in the condenser and evaporator giving you higher vent temps. Bugs and crud will block the orifice valve filter.

I usually dump the new compressor completely out into a graduated cylinder and re-fill with the same amount of fresh PAG or Ester oil. This is only the compressor part of the oil charge. Subtract the compressor oil charge you just poured in from the system oil charge found in the service manual. The remainder is the amount you load in your AC Charge Oil Injector tool and dump in the system after pulling a vacuum for at least 30 minutes & better yet an hour and making sure the vacuum holds for a full hour.

The charge weight you'll have when installing a non-factory refrigerant be it R134a or HFC152 or ... will not have any correlation to the original R12 refrigerant charge weight. There are several methods to charge the AC system with a non-original refrigerant. I learned from an old man that forgot more than I've ever learned about AC systems. This is a fair approximation of his method. https://67-72chevytrucks.com/vboard/...48&postcount=6

[L98camino]

Thanks all for the input.

Hatzie, since there is only one switch in my trucks system, wouldn’t that make it a binary switch? Is it possible that there isn’t enough of a refrigerant charge in the system to close the low pressure side of the switch? The switch is normally closed with the proper system charge but right now it is open. I ask because he said he put a partial charge in and the compressor didn’t cycle, tossed it back in my court said there was no voltage to the clutch. I have checked all the wiring for the system, no issues. I have power at the A/C Heat relay and controller in all the right places and the relay operates as it should. If I jumper the accumulator cycling switch connector (close the switch) the clutch engages.
I am not a great fan of this guy but we are trading firewood for his machine and services so I am kind of stuck with him. Our idiot Governor made it illegal to sell refrigerants of any kind over the counter at parts stores. You have to be a licensed A/C tech to purchase or service the system.
I back flushed all the lines, condenser and evaporator, serviced the compressor with fresh 134a compatible oil.
What do you think?
Dan