Bad Alternator ?

[BlazerLT]

Odd, sounds like a short of somethign somewhere.

[Alexxn 00 Si]

OK I'm opening this up again....I am on my second Bosch reman alternator and still having the same problem. It seems as though it's because these motors idle soo lom (600 RPM) If you lightly tap the accelerator the volts go normal. I am going to try a different brand of alternator now before I bite the bullet and pay for a GM alternator. Lucky for me to have a friend at NAPA who will take these back....

NOTE this NEVER happened with the original AC DELCO alternator....

[Alexxn 00 Si]

Cmon now with all of the GM techs on this board no one has any insight to whether this is normal or not ?? I know I'm not going crazy.....

[metallica21156]

i have something of the same problem. at night if i have my headlights on and come to a stop it goes slightly below the 14 mark but then recovers. it could just be a lazy regulator. and theres not much you can do about it other then changing it out. If i have the headlights on and the heat and the rear defroster and i'm sitting at a light it will be about 12-13 but as soon as i turn the rear defrost off or take off it recovers and is back up the the right voltage. you could always take it to a shop and have the alt tested to make sure its putting out the right amount of current and voltage.

[Rick Norwood]

Originally Posted by Alexxn 00 Si

Cmon now with all of the GM techs on this board no one has any insight to whether this is normal or not ?? I know I'm not going crazy.....

Check to make sure that the reman Alt is the same amperage rating as the Delco. You might be putting an undersized Alt in place of a higher rated one.

[berniescout]

pulley size?? a larger pulley on rebuild will cause the shaft to turn slower a smaller pulley would have the same effect as raising the idle speed or accelerating. recheck all electrical connections

[Alexxn 00 Si]

OK guys I'll double check all of that......thanks !

[Allbert]

Sounds like you might want to check the current draw on the alternator under the conditions when this happens. You'll have to hook an ammeter in series out of the alternator to do this, but if there's a short somewhere that's drawing a lot of current, better to find it sooner than later.

[Alexxn 00 Si]

OK so the new rebuilt alternator (not a Bosch this time) is 100 AMPS....all of the ones I've replaced so far have had the same sized pulley as well....does anyone know what AMP alternator comes stock on a 2000 4.3 Blazer LT ?

[Alexxn 00 Si]

Albert this happens anytime day or night, not everytime but mostly when I come to a stop and idle.....usually I only have the radio on...on occasion I did have the heated seat on but turned it and the radio off and no improvement.

[Cam1959]

hmmm ... assuming battery and alt still good, prob only when headlights on ? ... excessive current moving thru light circuits ... proper power draw lights ? ground wires and connections clean and tight ? bulb sockets in good condition ? i'd likely remove 1 bulb at a time to see if voltmeter improves, to locate actual light circuit prob if that cause. is headlight switch getting hot ? (short) also, isn't there a headlight power solenoid or something ?

[berniescout]

do you have trailer hitch wiring?? wonder if you have asalt build up between lighting circuit and ground!!!! only when light s are on ??

[chcknugget]

Mine dips to about 12V when my rear defroster is on, it's just a heavy load when idle.

[BlazerLT]

Originally Posted by chcknugget

Mine dips to about 12V when my rear defroster is on, it's just a heavy load when idle.

Something is wrong there.

Shouldn't dip like that. The engine rpms should raise a bit to counteract the load.

[blazee]

At night, headlights on (bright), defroster on, radio loud, amp and subs on, foot on the brakes (brake lights) mine dips just barely below 14....bounces slightly when using turn signal.