Ok, so I did a search before this and I didn't see exactly what I was needing help on so here we go. When the car is idleing the voltmeter will bounce between 11-14 volts and there is a chirping/ humming "high pitched" noise from the engine bay, when accelerating it speeds up then stops bouncing. Now at night when the lights are on the headlights and interior lights dim and brighten at the same rate as the volt gauge bounces and the chirping/ humming. I have never really had a problem with needing a jump battery is always up to the task of starting every morning, after about a week of sitting it may be a little slow but that is about it. Any help would be greatly appreciated.

Gabe

P.S. 1972 Chevelle, 350 not sure on the alternator though.

My first two guesses would be the alternator belt too loose or slipping,
OR, bad alternator bearings. Pull the belt off and spin the alternator by hand. If the bearing makes any noise or you can feel roughness in it, replace the bearings in the alternator.

Well the bearngs might make sense, I have that belt as tight as humanly possible, and I am no small human, and it will squeal if the engine is revved to quickly. Didn't think of that, and that would not let the alternator spin properly when the engine is idleing causing the voltage drop and light dimming I guess.

Another tip is the old "screwdriver handle in the ear" trick. With the engine running, carefully (repeat CAREFULLY) put the tip of a long screwdriver or sawed off broomstick on the bearing hub or case of the alternator. Press your ear to the other end. The sound will transmit right up and you can really hear a bad bushing/bearing.

Well the bearngs might make sense, I have that belt as tight as humanly possible, and I am no small human, and it will squeal if the engine is revved to quickly. Didn't think of that, and that would not let the alternator spin properly when the engine is idleing causing the voltage drop and light dimming I guess.

That's too tight and will burn up the bearings in the alt.

I also agree that the belt was probably already too worn (which caused the queaking) and you tightened it too much and wore out the bearings.

With the engine off, place your thumb in the middle of the longest span the belt makes between any two pulleys and give it a push - if the belt deflects more than 1/2" it is too loose. You then rotate the alternator out far enough so that there is minimal play (just remember that the longer the length of the belt, the more play is acceptable, so a 18 inch length of belt can have 1/4 to 1/3 inch of play approximately). If you have less than 1/4 inch of play, then you have it too tight.

In terms of "listening" to the engine, use a Mechanics Automotive Stethoscope. They are found everywhere for about $10.00 and are a lot safer than putting a fixed object up to your ear.

Find any feathers Lately?:D Could'nt help it.

Well, I replaced the belt because of the loose belt squealing issue, the chirping / humming noise was already a problem, I put on a shorter belt, the squealing noise got a lot better. I have been driving this car for the past year and a half and it has not gotten any worse. I guess my main concern is really the voltage spike and drop.

Another tip is the old "screwdriver handle in the ear" trick. With the engine running, carefully (repeat CAREFULLY) put the tip of a long screwdriver or sawed off broomstick on the bearing hub or case of the alternator. Press your ear to the other end. The sound will transmit right up and you can really hear a bad bushing/bearing.


So do you think using a "stubby" screwdriver is a bad idea?



I keed.......

Would you like an application for the 2009 "Darwin Award" sent to you now, or later??? :p:p