How long to leave vacuum pump running for an automotive A/C job?

[sh00ter]

After changing the compressor & accumulator, how long should I leave the pump running to ensure there is no moisture? Then very next question is how long to watch for leaks after shutting off the pump?

I've heard various times used (run/wait):

hour/hour
hour/10min
20min/hour

and other variations. The last time I did this I think I did an hour and an hour but I would like the shortest way possible

Also, I did not replace the evaporator or the condenser. How much oil can I expect to be left in those two components of a typical mid-sized vehicle?

Thanks guys!

 

[918evo]

After changing the compressor & accumulator, how long should I leave the pump running to ensure there is no moisture? Then very next question is how long to watch for leaks after shutting off the pump?

I've heard various times used (run/wait):

hour/hour
hour/10min
20min/hour

and other variations. The last time I did this I think I did an hour and an hour but I would like the shortest way possible

Also, I did not replace the evaporator or the condenser. How much oil can I expect to be left in those two components of a typical mid-sized vehicle?

Thanks guys!

More important than the time is the amount of vacuum pulled. I would want to see close to 30 in and typically pull 20 min and let it set 30 min or so. Every system holds a slightly different amount of PAG and different weights, so just use your judgment or look it up. On a 4 oz system, after replacing a hose and compressor, assuming the new compressor came without oil, I would put 1.5 to 2 oz in and call it good.

 

[sh00ter]

More important than the time is the amount of vacuum pulled. I would want to see close to 30 in and typically pull 20 min and let it set 30 min or so. Every system holds a slightly different amount of PAG and different weights, so just use your judgment or look it up. On a 4 oz system, after replacing a hose and compressor, assuming the new compressor came without oil, I would put 1.5 to 2 oz in and call it good.

Okay thanks, I left the pump running for 30min or more and then got busy so it has been sitting under vacuum for a few hours now so I think I'll be good.

As for the oil, the new compressor said on the back it contained 6.7oz of oil as shipped, but I dumped it out to check and it had 4oz. The system is supposedly a 4.5oz system total, so I just out the 4oz back in (minus the tad that stayed in the measuring cup), and figured there would be another half to an ounce in the evaporator. Hoping I did right since there would be no oil left in the accumulator since it was new. I was actually more worried about not having enough oil but maybe I'm fine. When I dumped the oil form the old compressor, it had an ounce in it so I figured the rest was in the old accumulator and evaporator core.