'97 K1500 AC High Side Pressure Dropping to Zero

Yesterday I received my replacement manifold gauge to try getting the AC running again on my truck, a 97 K1500 5.7 MT. Previously, I had changed the seals in the compressor, and replaced the orifice tube. I do have a new accumulator, but wanted to wait until I did a final leak check to put that in. I hooked the manifold gauge up, and tried to do the compressed air test that Paul has done in several videos. I only have a small pancake compressor, so I've mostly followed his Jeep series.

I was able to build up 90-92 psi on the low side, and it seemed to maintain it. But the high side, with the valve closed, didn't move at all. So I tried again with both sides open. The high side went up to around 125-130, but dropped back to zero. I tried to research an answer, but could only find examples where the high side might be low pressure, but at least had something, and that a clogged TXV might be at fault, which I don't have. As I said, I did put a new orifice tube in after fighting with the old one. The removal tool didn't work, so I had to take a pick with a slight angle to pull it out. I put it in the same direction as the old one, long screen facing condenser. The condenser tubing appeared to be very slightly bent, which probably contributed to how difficult it was to pull the o-tube out.

I'm not sure what it could be. I did an initial dye test a couple of weekends ago, and the only leak I found was at the compressor body itself. There was also some dye at low port itself, but that may just be spray from when I hooked it up and then removed it.

So when the High side went to 125-130 and went back to zero, did the low side still have pressure or did you lose all pressure?

The low side kept its pressure.

Brocktoon wrote: The low side kept its pressure.

I would check your manifold set.

If the low side held pressure then the high side should. Unless there is a major restriction in the system, I have seen it but usually only on a system with an expansion valve where the desiccant has broken free of the dryer and plugged up the passages on the high side.