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nostatic's Avatar
 
Join Date: Sep 2001
Location: SoCal
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idle gone: dying alternator?

I suspect my alternator has been going for some time...intermittant pulsing of lights (usually after the car sits for hours). It has been running perfectly but today when coming home I put on the headlights, then about 4 signals later it wouldn't idle...it would drop down and die. I could restart and if I kept my foot on the pedal a bit it ran fine. When I got home I turned off the headlights and it idled for a few seconds, then died.

Sound like an alternator that isn't doing it's job any more? I was actually supposed to get it replaced today but I had a meeting screw things up.

Old 01-06-2004, 04:20 PM
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You need to put a voltmeter on the battery. Your car should have about
14.2 to 14.5 at the battery with the engine running without any accessories.
Fully loaded (e.g. lights and A.C. compressor), the voltage should be over
13.5 volts.

If you need an alternator and have an external regulator one (Marchal)
DO NOT upgrade to an internal regulator one. Talk to Dave or Tyson at
TRE (Saw your car there a few weeks ago.). They can help diagnose the
problem.

Good Luck
Loren
'88 3.2
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Old 01-06-2004, 04:53 PM
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I've got an external, and won't be going to the combo unit (we've already talked about it). I didn't check tonight, but when my pulsing was going on I had spikes up to 15.5v, and that was with a new external VR. If I get some time tonight I'll check the voltage.
Old 01-06-2004, 04:55 PM
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Bosch alternators with an alternator light provide good diagnostic capabilities:

1. The light must be "on" with the key in the run position w/o engine started if not;
a. field winding is open or,
b. bulb is bad or,
c. brushes on regulator are bad or the regulator itself or,
d. slip rings are worn.

2. The light must be "off" when key is in "off" position if not then a shorted diode
in the alternator.

3. The light must go "off" when engine is started if not;
a. light glows dimly,
I. and does not get brighter at higher RPMs - poor connection from alt. to battery
II. light gets brighter at higher RPMs - an alt. diode is open or a field diode
is open
b. light glows brightly always - a shorted stator winding

Note: The gray type regulator (electronic) tends to be intermittent,
resulting in an overcharging condition (>14.7 is not good).
The old black ones (electro-mechanical) are the best.

Have Fun
Loren
'88 3.2
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Old 01-06-2004, 05:22 PM
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I swapped out my old (original I believe) VR for a new one when the problem first started, as I figured voltage spikes were VR related. It didn't cure it though. I've still got the old one, so maybe I'll use it with a rebuilt alternator.

The light doesn't do anything listed. The only issues I've had are pulsing lights that correspond to voltage spikes, and this latest die at idle. I thought I heard whining from the back yesterday and the day before too...figure maybe the bearings were going.
Old 01-06-2004, 05:27 PM
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Make sure that the noise suppressor is not plugged in series with the
regulator connector. Unplug the regulator and see if the whining goes
away. If the battery has a good charge, the engine should not die
at idle. You may also have a wiring problem.

It's time to stop guessing and begin testing things with a voltmeter.
Guessing always wastes time and money.

Good Luck
Loren
'88 3.2

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Loren
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'88 911 3.2
'04 GSXR1000
'01 Ducati 996
'03 BMW BCR - Gone
Old 01-06-2004, 05:35 PM
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