Bad Alternator?

[KillNThrill24]

Ok first off this isn't Mustang related, but I know we have some serious electrical gurus around here and I'm hopin one can help. Mainly lookin for Scott on this one

On my ZJ as some of you may know I've been experiencing some annoying electrical issues. First off my overhead display comes on and off as it chooses, and as of now will not come on at all. And the big problem I'm having is my head unit keeps shutting off when I'm braking. I figured bad ground, and Scott verified for me on my vehicle (93 Grand Cherokee) that the factory ground is no good so I made my own ground.

Everything was going smooth for awhile then tonight I went to Walmart and whaddya know it shut off on me again like the little bastard it is. So now I'm mother f'n this and mother f'n that and just pissed off because I still hadn't put my dash back on from the last time because I just knew this would happen. So I continued on to Walmart and as I get there I pull out my phone and go straight to Google (like any good mechanic does ) and then it clicked... It's not the ground causing all my issues, while it may not be helping either, but it's something else electrical related and I'm thinking alternator. As I brake I notice my in dash voltmeter drops down to ~11.2 if I had to make a rough estimate. The lights dim real bad too. Thats when it allll started making sense since it's been getting colder again the past few days.

So when I left Walmart I tested that theory out, driving without the heat on halfway home. No real problems, it cut out for a split second here and there when braking but never completely shut off. Then since I had it all figured out I verified it but turning on the heat. And whaddya know the first time I hit the brakes for a stop sign it shut off!

Long story short I figured out it's gotta be something like the alternator giving me issues. I'm not sure if it truly is the alternator because it's a fairly new looking alternator and the PO did say it had been replaced within the last year. But I'm not sure what else it could be. I went ahead and picked up some heavy duty (so the package claims haha) terminals while I was in Walmart and I'll start by replacing those because I know the posotive is cracked. Any leads on where to next would be greatly appreciated! I am considering the big 3 simply because 1: I do have a system in it and 2: I plan on adding more lights than are already on it. Sorry I type so much, I just like to be as informative as possible!

 

[ttocs]

if you see the insulation cracking then there is a very good chance the wire under it is coroding as well. If there is a connection under it then there is a good chance that its getting into the connection and could be causing resistance and causing your problem. A big 3 upgrade never hurts and when done right will negate my next suggestion of while sounding like a broken record, check your grounds..... In dealing with electrical we need to start simple and it doesn't get any more simple. At the vert least give them all a good pull/tug to make sure they do not move at all or else if you do not do the big 3 remove ground connections, clean the terminals and then retighten. A dab of grease over it will ensure that it stays clean.

 

[KillNThrill24]

Thanks Scott glad you responded buddy. No worries about sounding like a broken record I know for a fact it could always be something as simple as a bad ground somewhere throughout the vehicle. I'll check the main battery and body grounds and see what I come up with. I'll also clean the terminals on the battery again when I replace the wire terminals.

The big 3 just seems like something I should probably do since I am drawing a fairly large amount of power when I have my system up and all the lights on.

I did notice on the wire harness located in the driver side right about where you left foot rests, right above the kick panel, that the ground has definitely been tampered with and was grounded beneath the steering column. I didn't like how it looked so I added my own lead of 12g automotive wire and grounded it as well.

I'm hoping this gets resolved before to much longer, it gets quite boring driving in silence

Sent from my Galaxy Note 2

 

[CC'S95GT]

Did you notice any corrosion on the wire when you replaced the terminal ends of the battery cables?
do you have a multimeter?
the alt should put out around 14.7 vdc at any RPM. Ck that at the battery and at the alt itself.

 

[KillNThrill24]

Thanks man I haven't replaced the terminals yet will do that either tonight or sometime tomorrow. I do have a voltmeter so I can check everything out. The voltage on the dash drops bad when I let off the gas, even worse if I brake, which would be my guess as to why I'm having these issues. Like I said it drops to around the 11 area, everything dims real bad. We shall see tomorrow! I don't wanna fire it back up tonight, it's like starting the damn Mustang lol neighbors don't get to happy when I do it this late. Thanks for the advice I'll check to see what I'm at and go from there. If my voltage is low at the battery, bad battery and at the alt, bad alt right?

 

[MeanGrn Gt]

low voltage at the battery doesnt mean a bad battery also can be the alternator which will drain the battery. it should be 13+ with it running at the battery if the alternator is good. one thing i would check is while having the voltmeter hooked up checking the voltage while running is tapping the alternator with something. ran into this issue with a friends f150 a month ago. gauge was reading low and batt light popped on. by the time i got to my house with tools all of a sudden pulling in the voltage shot up and light popped off and checked it with a meter and it was good so thought it was just a fluke. so continued moving my shit with the truck to end up getting stranded by a dead batt. got it to autozone pulled the alt they checked it said it was fine. put it back on and it was still acting up in the parking lot. gets pointed out by one of the employees that aint a dumbass(like the one that tested it) that by jarring it might have made it make contact again and work intermitently. well it was dark and snowing by the time i got it back on and 10 degrees and dropping so i just tapped it while she was in watching the gauge and when it was good got it home and swapped in a new one the next day. whenever would hit a bump or slow down or speed up that was enough to cause the alternator to work or stop working

 

[CC'S95GT]

I would test the alt. from under the hood.
First connect the meter to the batt. red to red, black to black. With the car running, output should be @14.5vdc. Now raise the throttle and make sure the voltage stays the same.
If it's not @14.5 then put the pos. lead on the alternator output wire. (leave the black lead on the neg on the batt.) and make sure thevoltage is the same as when the leads were on the batt.
(if it's higher at the alt. than at the batt.) look at the alt. to batt. wire for corrosion.