Has anyone installed the suction throttle valve upgrade kit that old air and parts guy offers? Thoughts on the best way to bring the a/c back on line?

 

I suppose you are talking about the conversion to a cycling system that thermostatically engages and disengages the clutch. They essentially gut your original valve but from the outside it looks the same. If originality is not a concern then that is a reasonable approach but you will give up a little precision of temperature control but this is a cheaper solution than having your original rebuilt. I've seen one in operation and it worked reasonably well. The difference is that unlike the original in which the compressor stayed engaged whenever AC was requested while the valve controlled the flow now the compressor will cycle on and off.

One thing I suggest you add if it's not already present in the compressor connector is a reverse-biased diode (the arrow / cathode end pointing away from the ground connection) connected across the compressor leads as part of the plug. This will provide a path for the current when the thermostat opens and the clutch coil's field collapses and greatly extend the life of the thermostat's contacts. GM used this on many of their models and it really helped the add-on CoolPack AC units that did use a cycling compressor.

 

what's your current issue?

 

I appreciate the diode suggestion. I will definitely add that to the circuit. I suppose my issue is that the car has sat neglected for many years. Just trying to keep it original and have an air conditioner that works. Sounds like I need to overhaul the throttle valve.
Thanks for the explanation.
Brett

 

If you just can't get cold air, maybe run it through a vacuum pump and gauges and see if there's a leak.

If not, re-fill it with some R12 ($$$) and see if it gets cold.

If it gets cold, but then after awhile warms back up, then you may have an STV issue.

 

Almost no-one anymore can correctly repair the STV valves. Main problem is getting NOS replacement parts. This is a BIG issue for 1963 to 1966 Corvettes.

Regarding the STV bypass kits, the ones that use a pressure sensor do not work for our cars. Always ON-OFF-ON-OFF......etc etc. Maybe if the folks that sell the kits used a time delay type logic on pressure , it might work. But is also lacks refrigerant surge capacity on the suction side of the compressor. Later GM cars put the drier in the suction side and renamed it an accumulator.

The STV bypass kits with a temperature sensor to control compressor have a checkered history, with some folks reporting success and other reporting failure. If you live in a dry climate like AZ it may work fine, since the compressor does not need to cycle much since it is HOT outside and the humidity is LOW. In high humidity areas like Houston, TX or New Orleans, evaporator freeze-up typically occurs. The key besides humidity is placement of the temperature sensor so that response is good...... and accurate. A couple of degrees error can make all the difference.

If you have a 63-66 car with STV issues, you can try the STV bypass using temperature. If this does not work, replace the evaporator core and convert to POA valve like the 67 Corvettes. And rebuild the heater and AC boxes while you are at it to ensure good performance. OR convert to Vintage Air.

And make sure that the hot water shutoff valve to the heater core is working correctly and is not leaking hot water thru to the heater when you want good/max cooling.

Larry

 

Larry: Don't want to hijack the poster's thread, but I think this is relevant. I have a 66 Coupe, L79 with factory air. I have it at a shop right now to get the AC checked out. I am assuming that the heater and AC hasn't been working in at least 15 years, as the previous owner only drove the car about 500 miles (he says) during his ownership and the AC was not hooked up, water hoses to the heater core are looped. Missing the water shut off valve, but I purchased one of those. All other parts seem to be there and hoses attached, although some of the wiring is unplugged and I noticed the vacuum lines through the firewall were cut/not connected. So, I have not been able to have the compressor kick in, but obviously spins (though maybe not internal) when the engine runs.

I would love to stay stock, as many have said the stock system worked good, but I mainly want the AC to work as here in North Texas it gets hot and humid. I imagine they will check out the STV as part of their checking, and I figured they would have to change the dryer. I don't know if the system is still R12, I suspect from the time that it still is, but could be R134a. IF the whole system is toast, I figured my choices would be go with something like a Pro6ten for R134 and the STV bypass or eliminator, and as you point out above, the temperature sensor. Sounds like that is not ideal in hot humid weather?

If the STV is bad, you seem to suggest that changing to the 67 POA valve would be a better idea. So, is this something difficult to do? Would buying a new compressor, purchasing the 67 POA, and a 67 Evaporator be what is necessary to purchase and change? Does the rest of the system work together? I have a 66 AIM, but I assume I would have to get a 67 AIM to get the idea of parts and routing for the C60 originality?

Thanks very much for your comments and expertise. Hope it helps the original poster as well.