Join Date: Feb 2004
Location: Bloomingdale, Il
Re: My AC Gauge Reads -100 on Vacuum
Dye is used to pinpoint tiny leaks in a running system It is sold in small 1-2oz charges and is added thru low press port same way the system is charged. A leak will show up with a UV light. It can be useful in detecting a slowly leaking evaperator or condensor coil.
You really should check the system under high pressure (after all, it operates under pressure, not vacuum.) Vacuum testing will indicate big leaks right away. High pressure Nitrogen will show a small leak over a longer period of time, say overnight but the longer the better. Use Snoop, or LeakCheck, or whatever popular leak detection liquids to check all fittings or suspect flanges. FWIW, I have seen systems that would hold a vacuum, but not pressure.
Call a local hvac shop. They may charge you up with dry Nitrogen for a few bucks since you already have pulled a vacuum.
btw... Like everyone else has said... You want to pull a DEEP vacuum for an hour or more to insure ALL moisture is removed. 10 min simply isn't long enough. Some techs say 30 min or so vacuum pumping is ok, but if it's humid when the system is open, overnight sure won't hurt! .....Jb
Beat it to Fit, Paint it to Match!
Last edited by Johnny B; Jul 11th, 11 at 12:17 AM.