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Pressures OK and everything working but no cold air!

Holinder on Thu June 24, 2010 9:18 PM User is offline

Year: 1972
Make: Rolls Royce
Model: Silver Shadow
Refrigerant Type: R12
Pressure Low: 24psi
Country of Origin: United Kingdom

I have an Expansion Valve, Evaporator, Suction Throttling Valve, Compressor, Condenser, Receiver/Drier configuration.
Can measure down to 24psi at the Suction Throttling Valve with A/C full on.
No high side port to measure.
Compressor pipes hot and luke warm.
Liquid at the Sight Glass.
Outlet air at 70F with 85F outside ambient.
The 24psi would appear to indicate that the evaporator should be at 32F (using R12) but it isn't.
Any comments as to the problem, expansion valve? undercharged? compressor?

Fly like an eagle

Dougflas on Sat June 26, 2010 10:32 AM User is offline

Need high side pressure. You may have a reheat problem. Clamp off heater core hoses. If you can't find high side fitting, measure the high side line temp where the fitting should be and use a pressure /temp chart to get a guesstimate what high side is. When you state that there is liquid at sight glass, do you mean bubbles or a clear sight glass. Bubbles would indicate low charge.

Edited: Sat June 26, 2010 at 10:35 AM by Dougflas

chris142 on Sat June 26, 2010 10:54 AM User is offline

One would think that there would be a high side port somewhere but I'm not familiar with RR cars. Is the suction line cold back to the compressor?

bohica2xo on Sun June 27, 2010 2:50 AM User is offline

High side port should be at the rear of the A6 under the hood. Got long hoses?


"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 Sun June 27, 2010 6:54 AM User is offline

Does this kind of performance have anything to do with your overdressed queen sitting in the hot sun watching a tennis match with the ability for her to control her perspiration? A 70*F cool breeze would be more than welcome.

With Brad stating you have an A-6, and you stating that you have a sight glass gives strong indication you have a POA valve or that replacement valve I can't think of the name now, but does about the same thing. Nice of RR to keep that sight glass, GM dropped it here trying to sell you a charging station instead. We got around that by charging feeling the pulsations on the liquid line while also monitoring the inlet and outlet temperature of the evaporator lines. That POA would really throw you off. Would continue charging until those pulsations diminished, and the outlet temperature equaled the inlet temperature on the evaporator lines. This was hand felt of course, none of that digital temperature stuff.

Some added a sight glass to see the charge level, thats when, engine speed, 1,500 rpm, doors open, blower at max, and AC on was invented, just add the real Freon until those bubbles disappeared, at that time both evaporator lines should be of equal temperature and cold. With 24 psi on the low side, you are low on charge, should be 28.5 psi where the POA is set at. You could see a clear glass at idle, really not much going on at idle. Try it again at 1,500 rpm, assuming your POA is still good. Compressor runs constantly in these systems.

Have no idea where you are going to get some real Freon, but sure sounds like a low charge to me. Recall an RR dealer letting me sit in a RR back then, price was around $13,000.00 that sound extremely high, about the average price for a home. Today, if you walk into a dealership with $13K in your pocket, will take you way to the back to show you his wrecking yard.

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