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Re: Air Conditioning -- refrigerant charge question Posted by Tom G [Email] (#1951) [Profile/Gallery] (more from Tom G) on Fri, 8 Jun 2012 13:39:11 In Reply to: Air Conditioning -- refrigerant charge question, pme [Profile/Gallery] , Thu, 7 Jun 2012 13:38:50 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Here's a simplistic explanation base on my experience with A/C systems. I've been working on my own from the days of R-12.
Too little freon causes the compressor to cycle on and off, because the compressor causes the low pressure side of the system to drop below a predetermined threshold. The low pressure cut-off will cause the clutch to disengage. Once disengaged, the low pressure (vapor side) will experience an increase in pressure that will be greater than the "shut-off" threshold and the compressor clutch will re-engage.
Too much freon results in excessively high pressure which I've found reduces cooling efficiency.
I disagree with what Jimmy has said about using small cans. I've found that the threaded fittings on R-134 cans allow the freon to be safely added to the A/C system (as opposed to the old R-12 that held the valve in place by friction). However, I do use a manifold set when adding freon. Keep in mind that you should never (and I mean never) connect the small cans to the high pressure side because they may rupture (that why they have an indentation on the bottom of the can, so the bottom will blow out instead of the entire can rupturing).
From what you describe, your mechanic did absolutely the right thing by evacuating the system, weighing it and correctly adding the weight per the manufacture's specification.
I've had good results over the years. I haven't any cars that were so sensitive that slightly more or less would result in an A/C failure (GM, Chrysler, & Saab).
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