Automotive Air Conditioning Information Forum

I set up the vacuum pump for about 15 mins and then I shut off the valves. 10 hours later the next morning I checked it and it seems to have dropped a tenth. Could the difference in Ambient temperature be the cause of this? or do I still have a leak in the system. Could be a leak in the gauge fittings as well I suppose.

Likely just the system settling. A good electronic leak detector will tell in the long run.