Charging system (again)...

[Army_Dude]

I posted here about a week ago that my charging system was acting up. Dropping voltage it seemed like only in the morning and so on. Well a couple of nights ago I had to go out at midnight and jump a buddy off. I noticed while we were talking there was a grinding noise coming from the alternator. Tonight I replaced the alternator. Now I notice a visible brightening/dimming of my dash lights with the engine RPM's. Any thoughts on what I should check. BTW with the new alt the voltage is yet to dip below 13 on my gauge.

[79BIG10]

That's what happened to mine (dimming) before the modulator? went out in mine. I took mine in to a repair shop (not AZ) and he had it back to me rebuilt for $30 in a couple hours.

[Army_Dude]

Ok, I'm listening. Where is the modulator located? Is it something I can rebuild myself?

[Army_Dude]

UPDATE. My batt gauge is officially my new tach, lol. Took the kids to school and all was well. Running at about 15.5 on the gauge with radio,lights, and heat. On the way home I got caught at a light. When I stopped it dropped straight to 13. Light turns green and as I mash the gas it goes straight back to 15.5. BTW thats what I'm calling the line in between 13 and 18 on the gauge. Haven;t had the episode of a low reading and then the starter clicking on the next attempt to start again.

[evan]

Make sure your wires are all in good shape and connected properly. Car audio guys run into this problem a lot with big stereos, but old/crappy wires can cause it even without a stereo. They call it the "Big 3":
1) Alternator Positive to Battery Positive
2) Battery Negative to Chassis
3) Chassis to Engine Block

Most car audio guys usually upgrade to 1/0awg wire, but if you aren't running a big stereo system 4awg would be plenty.

[piecesparts]

Have someone put a load test on the alternator. If it doesn't cary voltage steady enough as you load it, then you have a bad diode inside it. Just because it is a replacement, doesn't mean that it was built right.

[Army_Dude]

Thanks guys, gonna start with my grounds and see where that leads me.

[79BIG10]

Something else is the belt. If the belt is worn then it can cause slack even though it's tight when not running but when started the slack can come in and then when you rev the engine the slack comes out and alternator kicks up the amps.

[tornado_tech]

I agree with the grounds and also the possible of a bad "reman" alternator. Had 2 reman alternators go out in same month and went with a different auto supply store (no more prob).