63 Riviera AC System troubleshooting

[Guest Steeleco]

As the AC on my 3 month old 1963 riviera is working (R134a), I am trying to troubleshoot some issures. As far as the vacuum goes I am manually opening vents etc. because some stuff has become frozen from rust etc. If the temperature is 95 degrees (as read at the center AC vent and I start the car and let the ac run including driving around for a while the lowest the air will get to at the vent is 65 degrees. There are bubbles in the site glass, the pressure looks about right according to my push on gauge. There is no vacuum at the STV which should mean it is set for max cooling. Can the valve fail and prevent max cooling. Any other suggestions are welcome. Thank you very much.

[Jim Cannon]

You also need to get the low-pressure side pressure readings to figure out what's going on.

You should get cooler than 65 deg. air out the center vent.

What do you know about the condition of the condenser (the coils in front of the radiator)? If it is still the original, you probably need a new one.

Was the filter/drier changed out when it was converted to R-134A? It needs to be.

Ignore the bubbles in the sight glass. That was there for R-12. Meaningless for R-134A. It is easy to overcharge an R-134A system with too much gas.

To get "like new" performance, you really need to rebuild the entire system. Personally I prefer R-12.

[Guest Steeleco]

Jim,

Thanks for the info. I definately agree with the preference of R12 over R134a. The condensor looks good (fins etc.) but obviously I can see inside it.

At some point I may rebuild the system. Currently, I just want to understand something about the STV valve. I understand it's basic function and have heard if it fails it should fail in the max cooling mode obvioulsly at that point it won't do it's job of keeping the system from icing up. My direct question is can the Suction Throttle Valve fail and limit the systems ability to max cool? Additionally can it be tweeked? I'm trying not to open the system, ie. disconnect any refrigerant lines.

Thanks again.

[Jim Cannon]

The STV controls the low pressure on the evaporator. It is, in fact, adjustable. See shop manual. That allows you to lower the suction pressure on the evaporator when you use R-134A for better cooling.

I doubt you should be doing that at this point.

Yes, if it is stuck, it is probably stuck on the max cool setting, so that's not your problem. A low pressure side reading will tell you that.

What pressures are you seeing? You say you have a gauge.

Try taking the car to an A/C shop to see what they say.