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Joined: Nov 2000
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OK... all facades aside... It's really the alternator in my truck...

My old alternator's bearings went kaput, so I got a new one from the parts store (the old one was still warranteed)...

The old one had a capacitor mounted on the exterior, the new one didn't, so I took the cap and put it on the new one... They were identical otherwise...

Well, the dern thing will only charge at an idle and doesn't charge very well then... It won't keep the battery charged when the wipers, blower and headlights are on... major voltage drop complete with sputtering motor.

Is it possible that the new alternator has a capacitor that is internal, or otherwise doesn't need the cap that I installed from the old one? Could the "doubled up" caps be causing the problem?

Another note, can't seem to get the belt tight enough for it to stop squeaking too... Might be most of the problem... (glazed?)

I'm going to replace the belt on Monday and see if it helps.

[Linked Image]


[This message has been edited by sparky66wv (edited 01-19-2002).]


-Virgil
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try the new one without the capacitor for a while and see what happens is my only guess.

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Virgil,

The Capacitor used with an Alternator for Autos is probably only there to reduce noise which would interfere with the ECM [Electronic Control Module - the on board Computer], or to get rid of the "Dentists' Drill Whining Sounds" that get impressed into the Audio system's Power Amp.

Question: How bad and at what speed does the drive belt slip / squeal?
Did it begin to squeal on the old Alternator, just prior to it's malfunction?
Have you charged the Battery with an AC to DC charger [a normal Battery charger] and if so, does it hold a charge or does it load the charger constantly [looking for shorted cell(s) in the Battery with this question].

I would verify the conditions of the Battery and make sure there's no equipment that is overloading [ignition coil, radio, etc.], then try getting the belt to not squeak [try running the belt over a bar of soap while the engine is at idle. that should get the belt to stop slipping on the pulley].

The slipping belt is indicating a very high load output [unless the belt/pulley assembly is loose or not fitting correctly]. It's trying to produce as much True Power [Wattage] as is requested, and this is derived from the Horse Power of the Gasoline Motor.

Try charging the Battery with it removed from the car's circuitry [disconnect the posts]. Charge it overnight [at least 6 hours] and see if the charge rate remains high or not.

Shorted cell[s] will make a Battery appear to work OK when lightly loaded [radio on, motor running, etc.]. The underlying problem becomes apparent when trying to start the motor. It either cranks very slowly then quits, or just will not crank at all.

Good luck!

Scott SET


Scott " 35 " Thompson
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i faintly recall something about 'polarizing' an alternator....

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Polarizing applies to generators. I have to do that with the old Harley generator.

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You can actually pull the caps on the battery and stick the probes of a meter into the electrolyte, testing from one cell to the next to find a shorted cell. (no volts)
Be sure to clean the probes off when your done of course.

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New belt...

Problem solved.

Upon closer inspection, I realized that I had the alternator completely against the stop, the belt was stretched beyond the adjustment range and had about an inch of play. (I coulda swore there was only 3/8" of play in it yesterday... hmmmm)

Oh, and thanks for the replies as always...

[This message has been edited by sparky66wv (edited 01-20-2002).]


-Virgil
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ah good! no excuses for monday then....

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Uh... Monday's a holiday...

The supplier is closed (I think)...

Excuses abound!


-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI

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