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Discussion Starter #1
I've posted about this before but I have a video now. I have a 2000 Mustang GT w/ 144,000 miles. When a/c is turned to "norm a/c", "max a/c", "Defrost", or "Mix", I get this really bad idle when parked. When I'm moving I can feel a huge power loss and a surging. The surging/rough idle gets worse as I turn up the power of the a/c. Here's a video showing exactly what happens when each item listed is on.
YouTube - ‪A/C Problems (2000 Mustang GT)‬‏
 

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Look at the AC compressor. Is it short cycling? Sure sounds like it.

It happens faster when the fan is on high because as more air moves across the coils, the pressure drops quicker.

Diagnosis: Low on Freon.

The Idle suffers because the AC does not run long enough for the PCM to re-learn new idle trim values. Further, each time the compressor kicks on/off, there is a small load change on the engine. The IAC can not respond to this change instantly.

The AC system was never designed to cycle so quickly.

The different mode settings really don't matter as the AC is still running.

From the previous thread, what happens when the AC low pressure switch is jumped? Does the idle improve?
 

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Discussion Starter #3
I've never "jumped a low pressure switch". I'm not even sure what you mean to be very honest. And on a side note, I for got to mention that I attempted to refill it with freon. When I did, I turned turned the knob on the can, and the gauge instantly went to the furthest pressure reading. So I'm guessing I over filled it somehow by only opening the can a little bit. I also bleed it out quite a bit I think.
 

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Did you LOOK at the AC compressor to see the clutch engaging/disengaging to confirm the symptom?

So what was the low pressure reading before the can valve was opened? Was it very low (< 30 PSI). What is the full PSI?

It's normal for the pressure reading to go up as a large amount of Freon goes into a nearly empty sytem. Remember, there's pressure inside the can and the gauges are calibrated for a running system.

Besides, it not possible for a system to go from nearly empty to over filled with a tiny crack of the Freon can. A typically car AC system would take (3-4) 12 oz cans of Freon.

You did keep the can upright correct? Charge only with gas.

Jumpering a switch involves using a scrap piece of wire to "jump" the electricity across the switch terminals. There by bypassing the normal function of the switch.

Perhaps you should rely on professionals for AC repairs. Serious personal injury is possible when AC work is done incorrectly.
 

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Discussion Starter #5
Today I took my car to Jiffy Lube for their "Full A/C Evacuation and Recharge Service". They did exactly that, and they filled it up to EXACTLY the right amount of freon. After they did that, they realized my clutch wasn't even engaging AT ALL.
 
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