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A/C system vacuum

by 1986chevyman on Aug 28 2018, 8:53 PM

Elite Tech

How long do you pull a vacuum on the A/C system after doing repair work? I usually like to pull at least 30 minutes on a single evaporator system and an hour on a dual evaporator system!!!

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7 Replies

By waylor22 Jun 13 2019, 12:56 PM

At least 30 minutes. Sometimes longer depending on current weather conditions and what was replaced

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By jeffreyd1 Jun 10 2019, 8:45 PM

At low temps with high humidity, we go a long time. Closer to an hour. During our hot,dry months 30 minutes is sufficient. Since water boils at 68 degrees at 28 inches of vacuum, if the outside temperature is less than that, we run the engine long enough to significantly increase underhood temps & then close the hood on the first click to create a "false ambient" temperature. If the ambient temp is less than 68 degrees, just 3 minutes is as good as it gets.

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By vannoortchris Jun 10 2019, 4:10 PM

Depends how busy we are... I always do 30 min but sometimes try to line it up with break or lunch to get a little more. More vacuum time is better.

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By knt auto sales Aug 31 2018, 2:49 PM

if the system has been open for a long period of time i like to vacuum for a longer period at min an hour. quick or short periods for repairs half hour works fine.

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By hfs454tech Aug 30 2018, 7:48 PM

if using new parts 30 mins should be fine

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By shadetreetech Aug 30 2018, 7:27 PM

Half an hour has always worked good for me.

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By sprintwrench4x Aug 30 2018, 3:49 PM

alot depends on how humid and how long the system is open. long time an hour... new parts quickly installed, half hour.

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