A/C Question

I'm working on removing my SBC 350 from my 1975 GMC C1500. It has factory A/C that doesn't work. Not sure what the issue is, probably the compressor. Anyway, what are the options to remove all the A/C bits and pieces (not sure how charged the system is still) and then put everything back together, get a new compressor, and charge the system with coolant that's compatible with what's in place?

Thanks.

There are only 4 main parts to the system:
Compressor, Condenser, Accumulator (drier) and Evaporator.

If you open it for any reason you should replace the accumulator/drier - this removes moisture.
You could start by replacing the compressor and drier which will usually solve the issue - if it is not electrical in nature.

That's about all I can help you with. I have a friend that does auto a/c work so I don't touch it.
When I did mine last year everything got replace so I could run whatever the latest refrigerant is.

It's not difficult but some procedures need to be followed. Any part not replaced needs to be flushed of oil and contaminates. In addition to previous post replace all lines and seals. Buy a conversion kit. Replace hoses if original, they are too old, 134A is a smaller molecule will leak easier. New hoses are made out of barrier material. Replacement compressors will work with 134A. Follow oil fill amount and total fill quantity. Will need to be vacuumed down before refill. Easiest to have a shop refill the system. If you want to do it yourself a gauge set, pump and scale will be needed. Not sure about Oregon but in Washington small cans of refrigerant are banned.

At this stage of the game and not knowing the charge status,what works,etc. I'd unbolt the compressor. Bungee it to one side, pull my engine and leave my AC alone until I had my drivetrain Ironed out. Less stuff to lose,no AC to discharge,etc. At this stage of the game for all you know it's charged and works but has no power to AC clutch etc.

Ricko1966 said:

At this stage of the game and not knowing the charge status,what works,etc. I'd unbolt the compressor. Bungee it to one side, pull my engine and leave my AC alone until I had my drivetrain Ironed out. Less stuff to lose,no AC to discharge,etc. At this stage if the game fir all you know it's charged and and but has no power to AC clutch etc.

Click to expand...

I'm with Rick on this one...

Unless you are prepared to do a complete overhaul of the system at the same time as the engine, just leave it be.

Also, first thing I would check is the charge on the system. If it is slightly charged it will not allow the compressor to start, it may just need a re-charge to start working again.

If the truck is still driveable, take somewhere to have the system evacuated. That will answer 2 big questions: does the system still have refrigerate (meaning no big leaks) and if in fact it still still charged that means your issue is electrical.

You’re probably going to find the system low on charge. The A6 compressor was designed long before the ozone layer was a concern, the front seal on the compressor is designed to leak. As the system leaks, it takes oil with it, keeping the seal lubricated. If you look at the underhood insulation of A6 equipped cars you can see a perfect outline of compressor oil spray pattern.

If the system has a partial charge, once it’s evacuated replace every o-ring, replace the hoses, and recharge.

The old A6 compressor is a true boat anchor, and it has heavy brackets to keep it supported. It’s also now old and not very reliable (do a search on A6 Black Death). It uses R12 and mineral oil, while current systems are usually R134 and PAG oil.

A complete explanation of how to convert or replace it would be quite long, since there are multiple choices to make as you go along. I did convert my ‘75 GMC to use a Sanden compressor and R134, and I learned a lot along the way.

For now I would just disconnect every A/C line, zip tie and tape a plastic bag over the end of the fitting to keep out moisture and dirt, and then remove the compressor.

75gmck25 said:

The old A6 compressor is a true boat anchor, and it has heavy brackets to keep it supported. It’s also now old and not very reliable (do a search on A6 Black Death). It uses R12 and mineral oil, while current systems are usually R134 and PAG oil.

A complete explanation of how to convert or replace it would be quite long, since there are multiple choices to make as you go along. I did convert my ‘75 GMC to use a Sanden compressor and R134, and I learned a lot along the way.

For now I would just disconnect every A/C line, zip tie and tape a plastic bag over the end of the fitting to keep out moisture and dirt, and then remove the compressor.

Click to expand...

Thanks for that. Do you have a write up on your conversion plan/path? I might look into that as it would be nice to have A/C on occasion.

I do not have a write up, but I have a lot of pictures and a list of everything used. This could motivate me to write it all down in one place.

It will definitely be easiest to go to the Sanden route if compressor needs to be replaced. Our 87 had a HR6 factory replacement (slightly shorty than A6) and the stock brackets that fit.
All after market bracket stuff is made for the Sanden types.

Sanden and an LS; you'll be in heaven.

75gmck25 said:

The old A6 compressor is a true boat anchor, and it has heavy brackets to keep it supported. It’s also now old and not very reliable (do a search on A6 Black Death). It uses R12 and mineral oil, while current systems are usually R134 and PAG oil.

A complete explanation of how to convert or replace it would be quite long, since there are multiple choices to make as you go along. I did convert my ‘75 GMC to use a Sanden compressor and R134, and I learned a lot along the way.

For now I would just disconnect every A/C line, zip tie and tape a plastic bag over the end of the fitting to keep out moisture and dirt, and then remove the compressor.

Click to expand...

The A6 is VERY reliable, other than the front seal is designed to leak. As long as the have oil in them, they are just about indestructible.

The A6 was so good, Harrison sold A/C components to ford, rolls Royce, jaguar, and a few other outside companies. The GM A/C systems of the late 50s to the mid 70s set the standard to which others were judged.

You will get no arguments that the are heavy!