1960s Anyone got HGBV adjustment experience with modern refrigerants?

[bigoilman]

I rebuilt mine but adjusting it makes little difference to the pressures. I got it down to 47# (spec is 30#) but that's all it'll do.  I'm using Envirosafe and the pressures should actually be lower than R12 or R134a specs but it's not happening.

System is blowing mid-high 40s air.  Maybe I'm expecting too much?  I'm used to getting low 40s output.

I added a 16" Spal pusher fan to the condenser too.

[bigoilman]

UPDATE: It's working better.  Didn't really do anything special. Pressures looked better right out of the gate this morning.  I ran the HGBV adjuster in all the way and then backed it out 1.5 turns and reassembled. Suction pressure at idle eventually settled at 34# and around 30/31# @ 1500(ish) RPM (no tach).  Took a short drive and air from the center vent was right around 40F at 40mph.  I'm sure it'll struggle in traffic but that's one of the drawbacks of these old systems right? If they were great, the manufacturers would still use them.

I made a little HGBV adjustment tool from a piece of SS tubing (a small screw driver worked just as well, though).

[Moody]

Glad it's working well. I suppose an  electric fan would help for low speed cooling, but then you'd have to deal with the noise of it. 

[bigoilman]

It's a little loud but worth it to help keep the A/C happy.  I've got dual 13" SPALs on my Turbocharged LS-swapped '77 C30 dually. Sounds like a jet taking off but it keeps the engine cool and A/C spitting snowballs even in 100 degree 90% humidity in stalled traffic.

[bigoilman]

One further update: I was underhood doing some other stuff and decided to make one more adjustment to the HGBV. Didn't hook up my gauges but took one more 1/4 turn CCW on the adjuster and took her for about a 40 minute ride. Center vent temps fell to 38 degrees!!  I'm not messing with it any more!  LOL

["Cadillac Kid" Greg Surfas 15364]

The HGBV systems were the state of the art in their day. The operator manually controls the compressor capacity and thus the systems capacity. The control was all manual. Good AC design has the air outlet (diffuser or grill) temperature 22 degrees below the desired space temperature for proper mixing of space and outlet air. Too cold and the outlet air just drops, leaving the upper spaces warm and below too cold. That said as control technology advanced Cadillac went to an electric/vacuum control of what is known as a "reheat" cycle where the air is first cooled and dehumidified to 33 or 34 degrees passing through the evaporator. The evaporator temperature is kept at a constant temperature via the POA.
Air is then partially diverted as necessary through the heating coil to provide a mixed air temperature as dictated by the control system modulating the reheat damper to deliver air to the outlets at something like 20 degree below the temperature dial setting. If the dial is set on 70 ideal outlet temperature would be around 50. To bypass the reheat a 65 degree setting of the dial and system at "max" shuts off the hot water valve and drives the mixing damper to the full cooling position. Then, on anything less than an 85 degree day outlet temperatures around 36-40 degrees will be experienced IF every thing in the refrigeration system is functioning correctly.
Just saying
Greg Surfas

[Dan LeBlanc]

I'd say you're getting pretty respectable vent temps using hydrocarbon refrigerant. I've heard they can fall on their face stuck in traffic though.

Has that been your experience, ir has it been good?

[bigoilman]

I'd say you're getting pretty respectable vent temps using hydrocarbon refrigerant. I've heard they can fall on their face stuck in traffic though.

Has that been your experience, ir has it been good?

Not enough "real world" driving to comment on any positives or shortcomings. Having worked with propane and isobutane (the components of Envirosafe) on a daily basis for the past 29 years, I don't expect any problems. If it "falls on its face" it won't be because of the refrigerant. It flashes off through the TXV just like R12 or R134a but does so at lower pressures.