Question: Orifice tube on 74 SB A/C?

[retired ralph]

Does this system have one? If so where is it? Part #? Thanks Ralph

 

[lars]

The GM '74 systems still used standard expansion valves. You can buy the expansion valve from any NAPA store.

 

[red vettes]

I don't know about '74, but '73 system is V.I.R. (valve in reciever) A few years ago they were available both new and rebuilt. I googled V.I.R. a/c system at that time to find them. Good luck

 

[lars]

I don't know about '74, but '73 system is V.I.R. (valve in reciever)

You're absolutely right - I had my years mixed up. 1974 used the VIR system, which combines the Expansion Valve, POA Valve and accumulator (which also acts as the Receiver-Drier) into one component that looks a lot like the earlier POA-system with separate expansion valve used through '72. The VIR system still uses an actual expansion valve, but it is integrated into the VIR assembly - there is no oriface tube on a '74. The difference between the two is that an oriface tube is a static device which creates a non-adjustable pressure drop through the evaporator. An actual expansion valve responds to low-side pressure (and superheat, if equipped with a sensing bulb) and self-adjusts. Rebuilt VIR's sell for around $170-$200.

Lars