1995 Mercury Cougar Air Conditioner draining battery

1995 MERCURY COUGAR
185,000 MILES • V8 • 2WD • AUTOMATIC
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TELTECH
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The air conditioner works fine while the car is being driven but at soon as you come to a stop and idle the battery gauge jumps down to .25

I had to replace the battery warning light fuse one time since the battery has been changed about 3 weeks ago.

The fuse has held up now for 2 weeks.

The battery and alternator are new.

Thanks,

Mike
May 21, 2008 at 11:24 AM
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RASMATAZ
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Could be that there's a problem with the idle speed control valve/motor-not raising the idle speed to compensate for the AC load. When the computer sense an electrical load it tells the idle air control to increase idle speed so that the alternator turn faster and produce more output voltage to maintain the electrical load.
May 21, 2008 at 2:15 PM
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TELTECH
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The engine idles very smoothly and does not seem to be any different than when the AC is off. The car never stalls or anything like that.

Could it still be the idle speed control valve?

The battery and alternator have been load tested and test good.

I can turn on all other accessories together and the battery gauge hardly moves.

Only the Air Conditioner drops the battery gauge.

Thanks for replying,
Mike
May 22, 2008 at 2:01 PM
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RASMATAZ
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As I mentioned earlier could be the ISC motor not functioning properly. AC dropping voltage could be be normal if not excessive..
May 22, 2008 at 5:52 PM