jeep ac problem

Leak test your gauges. Block off the service port to the vacuum pump and verify its capsble if pulling 30 inches Hg by itself.. Check the vacuum pump oil condition and level. If you have access to compressed air, and the system is discharged, remove the schrader valve from the yellow service hose, and fill the system with compressed air (psi = to ambient temp in F). Close off gauge valves to trap the pressure, and briefly run the system to achieve high side pressure of at least 200 psi, and quickly leak test accessible high and low sides of system with soapy water. Compressor shaft seal is usually not accessible for this test, so check plumbing, accumulator/dryer, compressor manifold connections, and condenser thouroughly. Look for evidence of luminescent refrigerant die at the evaporator drain valve under car. If and only if no leaks are found in any of these locations, then suspect shaft seal. Note: a leaking comp shaft seal will often sling refrigeration oil in a radial pattern. Inspection with a UV light may reveal this. Also, do not run compressor for more than a minute or so with the system full of air. Only long enough to bump up high side pressure enough to reveal a leak. It is also possible that the system holds refrigerant at a higher pressure but leaks down under vacuum due to the way internal pressure is exerted on seals, orings, etc.. By itself, the 24 inches isn't that concerning. You can just let the pump run a bit longer than tou would at 28-30 in. But something's definetely leaking if vacuum decays that rapidly. Good luck.