1979 454 C10, Factory Air

1979big10 said:

Howdy. I know this is my first post, but been using the forum for over a year to work on the 1979 C10 Big10 I bought out of a field in eastern CO last year. I have searched the forums have read up on the pros

I absolutely love the truck. Shamrock Green Metallic, 454/TH400, 8' bed. Silverado, factory cruise, A/C, but manual windows. I bought it non-running and have put about 10k miles on it in the last 12 months.
The factory air system is partially intact- the condenser and the evaporator are there (in unknown condition)- but the compressor, accumulator, and hoses are gone. I am unsure if this had an axial or radial compressor- I see conflicting info on LMC truck as well as the forums.

I want to add A/C back this spring, but am debating what route. Do I get a modern kit from Vintage Air, LMC Truck or Classic Auto (that uses factory ducting, not underdash), or do I build the system with factory components? From a quick look, Rock Auto and or LMC should be able to get me all the components and it would be a good bit cheaper than a Vintage Air or similar kit. Welcome any input or suggestions from people with experience here.

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1979big10 said:

This is what is there, looks like most of the bracketing is missing. From a quick glance I think Dirty Dingo has brackets to adapt to a Sanden 508, so I’ll probably go with that. But I welcome any input on vendors and sourcing these parts.

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75gmck25 said:

It takes a little searching, but there are kits to adapt and replace the old compressor and lines with newer compressors (usually Sanden). For example, the Pro6ten is an R134a Sanden compressor packaged as an exact bolt-in replacement for the A6. Some HVAC sites also sell adapters to bolt onto a Sanden so you can attach stock GM hoses.

General guidance
- original evaporator is fine if it has no leaks. Also make sure the evaporator temp probe and low temp cutoff works. That is what keeps the evaporator from freezing.
- original condenser is an old design, but so large that it may work fine with R134a. Parallel flow condenser would be more efficient, but you will need adapters or new hoses that fit the metric connectors.
- accumulator and/or filter/drier must be new
- original hoses should be replaced by new barrier hoses (however, old ones might work fine for a while)
- all new green o-rings
- pull vacuum for 30 minutes or more, and start with R134a charge to about 75% of recommended R12 amount. Tweak charge from there, based on pressures.
- most new compressors are pre-filled with PAG oil. All other components will need to be flushed to remove incompatible oils.
- R134 charging port adapters may be part of a new compressor, spliced into new hoses, etc.
- many sites recommend also adding a high pressure cutoff, but I have never seen pressures that were much higher than R12 pressures
- make sure your fan clutch is working, so you get good air flow.

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75gmck25 said:

No, but why do you ask?

I’m not sure whether it’s good or bad if you think I am AI!

I’ve been fixing and tweaking the A/C on my ‘75 K25 since about 2002, so it’s a long painful history.

The latest set of brackets I’m using for the Sanden compressor are made by Alan Grove (purchased from Summit). I used one version with the iron exhaust manifolds, and then switched to another version that worked better when I added headers. For the SBC think it was the 119L bracket to mount in the stock location but would have to look for my paperwork to verify.

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