Larry, thanks for the reply. The red dye is UV active as well, I have a UV LED flashlight coming. My question was mainly the vacuum reading on the low side. Both gauges read 30 psi without the compressor, but as soon as the compressor kicks in, the low side drops into vacuum, high side goes up to ~60 psi. I am assuming that I am low on freon, as I remember the low side was 45(?) and the high side ~ 180(?). What should they be in a properly functioning, correctly charged system? Thanks for the patience. Cheers!