A/C on - Volts drop,engine vibrates
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New User
Joined: Mar 2004
Posts: 23
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From: S. FL
A/C on - Volts drop,engine vibrates
For the past few days, when I turn on the A/C, I notice the Volt gauge drop (to the "N" or "O" in "NORMAL", when it's usually on the "M") and engine starts to stumble/vibrate (loss of RPM), but when I take out of gear and give it some throttle everything is OK.
This also can happen when coming to a stop when the A/C is on, but not always.
I've thoroughly tested the alternator and it's checking out great...14.7V @ the Bat with hi-beams on and blower fan on high. All tests of the regulator were also well within specs. Battery is pretty new and all wiring/grounds look fine.
Does this have anything to do with the A/C "cycle switch" (not sure of the name) that's part of the dryer? Does this inform the PCM that the a/c is on (clutch engaged) and to supply more fuel to compensate for compressor drag?
Any other ideas?
This is for a '93 Ranger, 2.3L, manual tranny.
Thanks!
This also can happen when coming to a stop when the A/C is on, but not always.
I've thoroughly tested the alternator and it's checking out great...14.7V @ the Bat with hi-beams on and blower fan on high. All tests of the regulator were also well within specs. Battery is pretty new and all wiring/grounds look fine.
Does this have anything to do with the A/C "cycle switch" (not sure of the name) that's part of the dryer? Does this inform the PCM that the a/c is on (clutch engaged) and to supply more fuel to compensate for compressor drag?
Any other ideas?
This is for a '93 Ranger, 2.3L, manual tranny.
Thanks!
Post Fiend
Joined: Jan 2003
Posts: 9,748
Likes: 16
From: Connecticut
Did you test the alternator when A/C compressor was running?
The PCM is indeed programmed to raise idle speed in order to account for the additional load that the A/C puts on the engine. I believe the cycling switch is the input for this. But this adjustment (allowing a little bit more air and fuel in) happens only during idle and deceleration (i.e., closed throttle), not at part throttle. The PCM is also programmed to cut off the A/C compressor at WOT.
The PCM is indeed programmed to raise idle speed in order to account for the additional load that the A/C puts on the engine. I believe the cycling switch is the input for this. But this adjustment (allowing a little bit more air and fuel in) happens only during idle and deceleration (i.e., closed throttle), not at part throttle. The PCM is also programmed to cut off the A/C compressor at WOT.
Thread Starter
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New User
Joined: Mar 2004
Posts: 23
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From: S. FL
Yeah, I did also check w/ a/c on, but had to "goose" the throttle a few times before it would hold a steady idle. I don't recall exactly, but know the Voltage was still above 14. And I should have stated in my original post that this only happens when I turn the a/c on at idle (at a stop light or before leaving home) and then when idling down to a stop when a/c on, so it probably is this "cycle switch".
I'll double check the belt as well...
Thanks for the replies
I'll double check the belt as well...
Thanks for the replies
