{"id":6117,"date":"2026-08-21T07:43:46","date_gmt":"2026-08-21T11:43:46","guid":{"rendered":"https:\/\/kgworks.ca\/?p=6117"},"modified":"2026-08-21T07:43:46","modified_gmt":"2026-08-21T11:43:46","slug":"ac-time","status":"publish","type":"post","link":"https:\/\/kgworks.ca\/?p=6117","title":{"rendered":"AC time"},"content":{"rendered":"\n
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A tin pie plate and a flattened tin pie plate – so what!<\/p>\n\n\n\n

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I don’t have any original insulation for the temperature sensor on the side of the expansion tube so I’m using a double wrap of header insulating tape. If it can keep heat in it should be able to keep heat out.<\/p>\n\n\n\n

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And now for the pie plate. I cut out a portion of the heavy aluminum and wrapped it over the exhaust manifold tape to help deflect the heat that will be coming from the exhaust manifold that is less than 6″ away. I may also cover the heater box in heat deflecting sheeting (that is also used on fire walls, floors, and engine hoods) to help keep heat away from the AC system.<\/p>\n\n\n\n

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AC gauges hooked up to the low (blue) and high (red) pressure fittings. I am using adapters on the original R12 fittings so I can attach the R134A fittings on the AC gauge hoses. I will be filling the system with R12A a substitute for R12.<\/p>\n\n\n\n

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It is at this point that my inexperience with AC begins to show. I realized I hadn’t considered the oil needed in the system. The manual says that it needs 6 oz of oil. Checking at NAPA I found that it needed PAG46 oil for ’79 Chevys. Now I needed to know how much oil was already in the compressor. I couldn’t for the life of me find the compressor information slip so no choice but to remove the unit. Turns out there was just enough to keep the unit oily inside.<\/p>\n\n\n\n

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Checking the internet I found that 2oz of oil should go into each of the compressor, condenser and dryer. In the photo the high\/low pressure connection is back on the compressor. While it was off I was able to get 3-1\\2 oz into the condenser line and I put 2-1\/2 oz in the compressor – A compromise since I couldn’t get any into the dryer.<\/p>\n\n\n\n

With everything hooked up it was time to vacuum down the system.<\/p>\n\n\n\n

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Here the vacuum is pump hooked up. I’ve used it a couple of times so it has paid for itself. A pump and a set of gauges plus a few fittings is all that is needed to service an AC system. There are a lot of videos and information on line on how to do the work.<\/p>\n\n\n\n

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Pump started and the gauge ( blue is showing a 30 lb vacuum that will be plenty to cause any vapour in the system to boil and be vacuumed out. I ran the pump for about 1\/2 hour and then shut off the red and blue lines to see if it would hold vacuum. Sadly the gauge slowly dropped down to zero. It is likely a pin hole size leak and maybe even in the gauges. I’ll add a can of stop leak to the mix when I charge the system.<\/p>\n\n\n\n

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The low pressure gauge (blue) shows the vacuum starting to fall.<\/p>\n\n\n\n

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The system needs approx 16.5 oz of R12A which is less than if it was charged with R12 – I got the conversion from the web. Two 6 oz cans of R12A and one 4 oz can of system sealant.<\/p>\n\n\n\n

The AC low pressure switch turned on and started the compressor with less than one can of R12. It was cycling quite quickly and each time the compressor started it would suck in a bunch more coolant. I next added the sealant and went on to the second can of R12A. By the time I had most of the second can of coolant loaded the compressor was in operating almost continuously which I understand to be correct.<\/p>\n\n\n\n

I took the Chevy out for a run and the AC is working beautifully. It will take time to see if I am loosing gas or the system is sealed properly. In the meantime I’ll enjoy being able to keep the windows up on hot days.<\/p>\n\n\n\n

Next: this about ends my work on the Chevy until the fall when I will be re-doing the front end and adding cruise control to the car.<\/p>\n","protected":false},"excerpt":{"rendered":"

A tin pie plate and a flattened tin pie plate – so what! I don’t have any original insulation for the temperature sensor on the side of the expansion tube so I’m using a double wrap of header insulating tape. If it can keep heat in it should be able to keep heat out. And … <\/p>\n

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