I've been through 124 expansion valves a few times, and it looks OK to me. Pretty impressive photo for such a tight spot!, BTW.

I can see the suction line is seated in the ex. valve all the way up to the shoulder, with the o-ring hidden from view. This is how mine seats as well.

The o-rings are just standard metric sizes, so it's very unlikely you have incorrect sizes.

Colors of o-rings don't mean anything. Usually HBNR is light green, and blue or black are neoprene. But not always... Either neoprene or HBNR should be fine for an R-12 or R-134a system.

Give it the old vacuum test as Larry described. The proof is always in the pudding. One caveat. I presume the system has been used recently, and that you've not completely flushed all the old oil and replaced the drier? If so, you can expect the vacuum gauge to not hold steady after a short evacuation. Here's why. Refrigerant is disolved in the oil inside the system. It will stay there a surprisingly long time, even with the system open to atmospheric pressure. As you pull a vacuum on the system, the refrigerant will start to come out of the oil. If you give it sufficient time, enough refrigerant will be released to affect the vacuum reading. I find it takes 2-3 hours under full vacuum to get all the refrigerant out. After that, see if the system will hold vacuum long term.

- JimY
- JimY