Hi Neil,
At 90 degrees F, the low-pressure side should have been between 50 and 55 psi. I can't guarantee it, but I feel it is simply low on charge.
As far as the expansion valve, it is responsible for a few things, but I don't think by itself it would cause the pressure to be low and the system working as described.
Try adding refrigerant. See if that takes care of it.
Let me know.
Joe
Monday, July 8th, 2024 AT 6:58 PM