control valve?

[garthr]

hey, i am working on an old milk truck with these truck plates for cooling. on the piping to these plates, is what looks like maybe a three way valve? anyhow, it has a small diameter tube coming from the top. at the other end of the tube is a bulb. Question; what does this valve do and the bulb has broken off from vibration. will this affect operation or should the bulb be brazed back on? does the tube contain a gas or a vacuum? its hard to red numbers from the top of the valve but a number 8448 is visible. the fridge compartment has valves that look the same and rcd 1/4 fw r12 8431 can be read on the tops.
thanks

[lowcool]

gday garth
i would say its a thermostatic expansion valve.that bulb is the thermo bulb measuring suction line(evaporator) temperature allowing valve to regulate the flow of refrigerant.by the numbers it may be a sporlan valve but replacement will require a reprocessing of the system.in short the valve is stuffed and your gonna need a fridgy.
cheers