Does anyone have a picture of a 63 to 67 expansion valve taken apart? My 63 valve is stuck shut and I'm trying to figure out the cause. Firstly I'm just trying to figure out what suppose to be inside the thing.
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Re: A/C Expansion Valve
Harry:
No "exploded view". Sorry.
A hot bulb temperature will try to open the valve and a cold bulb temperature will try to close it. Since the exp valve is filled with refrigerant, high temperature = high pressure = valve open. I would say that you lost the refrigerant change in the bulb/capillary and that is the reason that the valve is closed. Could be a pinhole leak or a ruptured or deteriorated diaphragm in the valve. Only one or two places "claim" to repair or restore them, and I am not sure that they really can. I think you already tried/contacted one, correct??
Larry -
Re: A/C Expansion Valve
I've attached 3 pictures, one with the valve apart. I can blow air through the main body with it apart. The part with the arrows appears to be the problem when I put it back together without that part air will flow. When I install the part air will not flow. Thoughts?
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Re: A/C Expansion Valve
Harry, I'm no expert on automotive A/C TXV's (expansion valves) but refrigeration and home/commercial TXV's work like this. The pressure that the bulb creates added to the spring pressure in relation to the evaporator pressure determined the superheat setting.
Simply put all TXV's that I've ever serviced cant just be taken apart, cleaned and re-assembled, the superheat setting will be incorrect. Since the screw that puts pressure on the spring is internal It's not practical to set the superheat on these types of valves since an adjustemt requires a dissasembly of the valve.
I could be wrong in all this but if you counted the number of turns that it took to remove the spring you might be OK.
Additionally, if the bulb was discharged the spring pressure will close the valve, could be your problem and the valve will need to be replaced anyway. Not sure if it helps, I hope so.Comment
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Re: A/C Expansion Valve
Tom, thanks that helps.
I was talking today with an A/C tech. He said that you should be able to blow air through the valve when it's at room temperature. If you can't then it's jammed closed. Saying that, pressure in the bulb would have no affect at room temperature.
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Re: A/C Expansion Valve
To the expansion valve, room temperature (70 F or so) is "hot", so yes the valve will be open. As Tom said, the valve tries to control the evaporator refrigerant SUPERHEAT temperature to about +10 F, so it is probably set to try and hold around 40-45 F or so (evaporator outlet refrigerant temperature).
All the C2 Corvette expansion valves are external balance design, so you should have an additional pressure tubing connection on the valve. This further complicates the rebuilding/repair as it adds additional complexity. Also, I believe that the expansion valve will never close completely and deadhead the A6 compressor. It should always pass a minimum refrigerant flow. That is why you have the STV (or POA for 1967) valve in the system…………….to keep the evaporator from getting too cold and freezing off under cool ambient conditions and low compressor/system load.
Not everything in these old cars was meant to be repaired in your garage. This is one of them.
LarryComment
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Re: A/C Expansion Valve
For got they were externally equalized, most smaller valves are usually internally equalized. The reason that an externally equalized valve is used is to compensate for the pressure drop between the inlet and outlet of the evaporator. Makes maintaing the correct superheat easier for the valve. The last thing you want is zero degrees superheat, makes compressors fail very quickly.Comment
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Re: A/C Expansion Valve
Think I'll just put it on the shelf and use another one I have.
Thanks All!
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