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R12 Charge for 67 Eldorado

cadillacproject on Mon July 20, 2009 11:12 PM User is offline

Year: 1967
Make: Cadillac
Model: Eldorado
Engine Size: 429
Refrigerant Type: R12
Ambient Temp: 90
Pressure Low: 35
Pressure High: 220
Country of Origin: United States

Hi all. Just wanted to thank you all for the great advice. I installed one of the parallel flow condesners in my 67 eldorado and WOW. I am usring R12 and it works great. Get 42F at 1500 RPM and outside temp of 90+ and super humid. Big big difference from the stock condenser.

Here is my question. The factory shop manual says to charge with 64 oz. of R12. I have put in 50 oz. After a perfect vacuum etc. The sight glass is clear and its cooling very nicely. Should I put in the final 14 oz or leave well enought alone? this system has a POA and is now restored to original stock condition with a new expansion valve rebuilt POA and a brand new parallel flow condenser ( not stock of course ).

bohica2xo on Mon July 20, 2009 11:18 PM User is offline

R12 & a working sightglass, great system.

If you have a clear sightglass, you have enough refrigerant. Simple as that. Add 1 to 2 ounces after clearing the sightglass, no more than that. The PF condensor does not need as much refrigerant.

Great to hear you have kept that system in place.


"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

NickD on Mon July 20, 2009 11:51 PM User is offline

Old timers swear that the most accurate way to charge a system is with a sight glass, but what would I know, I am just a kid. The proper way to do it, is to wait for at least an 80*F day, 85*F is fine, doors open, AC on, blower at max with the engine running at 1,500 in the case of your domestic V-8 engine.

My preference, ( remember, I am just a kid) is to charge just until you see a couple of bubbles floating past the gauge, this is providing near solid liquid to the orifice, variable in your case, another reason for the warm day, and the doors open, you want that sucker to be wide open to maintain that almost pure liquid state.

Adding more refrigerant does not increase the cooling, what it does is to fill up the reservoir, or receiver in your case. The reason the OE's do this is so that in the event of a small leak, system will make it through the warranty period without complaints. But since you own your own can of R-12, you can always add some, but the big thing, under the same exact conditions, if you see more bubbles in the glass, you know you have a leak that needs attending too. But if you fill up the reservoir, all that R-12 in that reservoir will be gone forever before you have that visual indication of a leak. Don't feel you want that.

If you are skeptic, no harm in monitoring your pressures with gauges, course, make sure both valves are closed, but POA systems are a bit tricky as your compressor is effectively being bypassed. But the low side should hold steady, believe at 28.5 psi.

Those old POA system worked great and can't be imagination when driving in a 120*F ambient with the inside temperature at 65*F. AC's were fairly new at that time, and anything would have seemed better. Sure you have climate control, could set that on your bench, apply 12V and a vacuum source and watch them work, none of the voltmeter stuff, had one transistor to control the blend door motor, easy and cheap to repair. Used a resistor substitution box to emulate the in-car sensor. Mostly needed cleaning and a tad of oil on the door bushings to get them working properly.

The good old days, but what do I know, I am just a kid.

cadillacproject on Tue July 21, 2009 8:44 AM User is offline

cadillacproject on Tue July 21, 2009 8:45 AM User is offline

I will for sure trust the sight glass. Thank you all for the help this makes perfect sense.

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