Autozone lent me this really nice gauge and hose set. Trouble is, I'm not 100% on how to use it.

1. I hooked the red line to the high side, the blue line to the low side. It's impossible to get those backwards.

2. I started the engine and turned-on the AC so that the compressor was running.

3. I opened the thumb screw on each hose, down at the connection points to the A/C.

4. I opened the low side valve up at the gauge, and the needle moved, apparently depicting the amount of pressure in the low side of the system.

5. When I opened the high side, the high gauge moved, but ALSO the low side skyrocketed and peaked.

This was what confused me. If the value is opened at the low side gauge and I open the value at the high side gauge, does the high side pressure for some reason bleed over to the low side gauge?

When I closed the low side value at the gauge, then both gauges seemed to correctly show the pressures.

Was it wrong to have both valves open at the same time?

If I am doing it wrong, what is the CORRECT procedure to hook up, open valves, etc.?

 

Ok, nevermind...

I actually sat down and read a manual to one of those gauge sets.

It looks like the gauges show the pressures even when the manifold valves are closed. Apparently, the manifold valves are only for adding stuff to, or removing stuff from the system via the yellow hose.

 

I'm glad you read the booklet, I was going to suggest that but you found it yourself..

Good !