Laserjohn

My alternator evidently went dead, and for the last couple of weeks, my Sears DIEHARD finally died HARD!:cry

I replaced the alternator and the battery won't hold a charge, so I have to get that replaced.

My question is...if the car is started and running (with the new alternator), and I put a current clamp on the +battery, and I turn on the lights. The ammeter shoots up to about 13 amps, OK,...but then if I leave the lights on, the current slowly decreases and keeps decreasing, I turned it off before it got to far down.

My main question is, shouldn't the alternator be able to support the entire car's power requirements? The battery will be changed at lunchtime today, and I will see if I have the same problem. But any ideas as to the alternator current decreasing? :confused: :confused:


[Modified by Laserjohn, 8:09 AM 3/18/2004]

68raggtop

First, I am no expert but I think this is correct. The ammeter is showing the direction of current flow, not battery voltage. When you turn on the headlights etc. the draw on the battery increases, which means the output must increase (thats the 13 amp increase), at a higher rate than the draw. As the battery regains its capacity the ammeter will show a gradually decrease in current flow, back to near normal reading. :cheers:

Laserjohn

The lights dim as the current goes down though....like the alternator is slowly dying again, I'll check it out again after lunch when I have a new battery. Thanks.

BigBadRed

Get the alternator checked. Sometimes putting a new alternator on a dying or dead battery will fry it.

stpman

:iagree: Some of the new alternators come with a warning about making sure the battery is fully charged before running. (my 93 Jimmy)

Steve :steering:


[Modified by stpman, 12:20 PM 3/18/2004]

cardo0

Your right John your alternator is poop. You have to stay ahead of the charging system as a battery with a shorted cell or sulfated from contiuoulsy drained condition will draw from the alternator until the diodes burn up or quit. Also running continuously off the battery while alternator is bad can cause that sulfated battery condition (ruin it).
So I guess what I advise is have them both tested. Use a battery tester (load cell) to test battery and not just a voltmeter. Also a alternator needs to but out over 13.6 volts to charge a lead acid battery and needs to run higher rpm than at idle. What this means is that at idle you are usually measuring just batterry voltage and when you rev it up (over 1,500 rpm) you can measure alternator output. :yesnod:
Good luck :seeya