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1973 Pontiac R-12 capacity

Karl on Fri October 22, 2010 6:50 PM User is offline

Year: 1973
Make: Pontiac
Model: Formula
Engine Size: 400
Refrigerant Type: R-12
Country of Origin: United States

Okay, I have a question for the gurus!!!

I have a 1973 Pontiac Formula and want to know the capacity for the R-12. The sticker on the compressor says 3-3/4lbs I have a 1973 motors book that shows up to 70-72 takes 4-1/8 lbs. It doesn't list 73 even though it is a 73 book?!

I had to get some used refrigerant lines off ebay, because mine was missing the muffler assembly, and I believe they are from a 73 maybe 72. If they are the same as 72, why such a different amount of R-12?

When the muffler assembly was missing,(which to me is a lot of piping/hose, I am assuming it was still charged with 3-3/4lbs. the car would blow almost 37 degrees cold air . It was awesome.

I just don't want to overcharge it if it is a bad thing. I mean I am only talking by 6 ounces.


Chick on Fri October 22, 2010 10:33 PM User is offlineView users profile

Start with the 3 3/4 and then check the sight glass, charge until it's clear... Your drier should have a sight glass.. I can't remember clearly, but if you have a VIR it will be on the side of that.... Maybe someone else can remember back that far..I have trouble remembering what I had for breakfast lately....

Email: Chick


Freedoms just another word for nothing left to lose

NickD on Sat October 23, 2010 9:10 AM User is offline

What I can remember during that era, pay 11 times more for fuel tax, had better roads back then, 17 times more for property taxes, had better schools back then, 16 times more for FICA taxes, could live on SS benefits back then, and 30 times more for medical expenses, had better doctors back then.

Was surprised that guy with a 71 Corvette had a sight glass on his car, must be an aftermarket one, GM quit using these around 62-64 and were trying to push a charging station instead. Ten times as much about how to that thing then explaining the AC in their shop manuals. Old timers were installing sight glasses, the only way they knew how to properly charge a vehicle without spending huge bucks on that charging station. But again rules had to be followed, AC on, blower at max, doors open, and engine running at 1,500 rpm, some things just don't change, and for most accurate results, do this on a above 80*F day. Kind of a limitation. Charging until the evaporator outlet reduced its temperature to the inlet was one trick, a finely tuned hand could feel impulses on the liquid line, charge until those pulsations diminished.

Not quite sure if this 73 is still using the POA, sometime in that time frame the CCOT, or an evaporator temperature sensor came into play and the compressor started to cycle, that was new and unimproved. Can always cheat and look under the hood. Did have a stack of shop service manuals from that era when you could buy them postpaid for four bucks each. But had to get rid of all that stuff. Mufflers seem to be optional, most GM vehicles didn't have them, and Pontiac was a completely separate division from GM, even made their own engines and transmissions. In the late 70's and 80's couldn't tell the difference between a Chevy or a Cadillac unless you looked the nametag. It tends to become a blur.

What is breakfast?

Karl on Tue November 02, 2010 8:31 PM User is offline

Thanks guys, was out of town for the last week and a half. This does have a POA valve and not VIR. The R/D does have a sight glass. Right before I left out of town, I filled it with 4 1/8 lbs of R-12. It was 65 degrees outside, and the my gauges were showing about 31 on low side and (I forget now) 120 or 125 on high. Granted this was at idle. I took the car out for a drive and was getting 43 degrees out of the vents.

Now the OAT is about 50 degrees, so I'll have to wait for spring to do anything else with it. I figured check pressures, like was mentioned, do on a day above 80*F degrees.

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