battery arched while driving, blown alternator

[Throwback23]

So tonight I was driving and noticed that my cd player was flickering on and off, then my airbag light came on and turn signals wouldn't work...I was in panic mode in ..Well I pulled into my house and instantly noticed one of my ground wraps had came off and had been grounding my battery for an unknown amount of time as I drove. Well I proceded to test battery voltage and it was crazy low at 11.5v and altornator output came out to zero. Alt choke fuse was fine so off with the alt tommorow to be tested... I guess after this anything is possible, blows my mind the random garbage that can cost a pretty penny. Anyone ever had an experience like this?

 

[DSM1G90]

DC current flows from negative to positive why the arcing when the ground cable came off - why it's totally important to have as much grounds as possible from the battery ... and very clean and tight connections.

Saw one vehicle in a parking lot with a similar condition - weak ground cable from battery to chassis and sparking very crazy .. he began an engine fire from the fumes coming from the carburetor.

Good luck and glad you made it home.

-DSM

 

[Throwback23]

Well not sure how to explain it but pulled the alt since it wasn't giving me anything, had it tested five times and it passed every time. I proceeded to reinstall it and now its money...like it never happened. I haven't looked at the diagram for the charging circuit but only way I could explain it is if maybe there is a circuit breaker involved? Either way, glad to be on the road without any money involved

 

[Awd-laser]

I had a friend of mine (at the time) have this same "arcing" issue on a 1g plymouth laser. It had blown the alternator fuse and caused the battery to arc to the hood and actually burned a hole in the his hood. Glad to hear you didnt have to spend any money to get her back on the road...always a plus.

 

[Throwback23]

We'll I guess it was bound to come back....thus time I was ready and logged the issue. So after about 3 minutes of driving I noticed my cd player kept shutting off so I pulled my laptop out and started logging... I was at 8.8v so I assume that whole drive was on battery alone up to that point so I did what I could to get home asap. Well voltage was staying around 8.8-8.6v then hit a low of 8.5v then out of nowhere bam 12.6v the whole rest of the 5 miles home. The alternator test fine but that sounds like a possible internal voltage regulator issue and there's no way I can trust it.

 

[Throwback23]

So over the last few days I've been monitoring voltage and its pretty weird...the voltage will only go as high as 13.3v when charging which seems lower then usual. The alt still works like 90% of the time but then randomly cuts off, I wasn't sure if the alt was dropping to 8v or if it was just letting me run off battery but sure enough when I saw the volts dip i ran out and pulled the positive terminal and it died so I am ready to quit testing and junk the alt. Seems crazy that it would test good and be so junky ... figures though

 

[Awd-laser]

Well i'm glad you have a better idea of what the problem is...keep us posted if that was indeed the issue

 

[CellerDweller]

In automotive testing your situation would be called a "load dump" test on the alternator. I used to test Delco Remy and Denso alternators where we quickly open the circuit under full load of the alternator. Most of the time the alternator survives, but in some occasions the electronics in the regulator or diodes in the rectifier get damaged. The reason for this is the energy in the alternator coil (inductance) needs to go somewhere and since the return path (ground wire) is broken, the energy finds a path to ground through the electronics.

This can sometimes take out an ECU, so you may have gotten off lucky with just an alternator. If your handy, like most DSM'ers, and can find a rebuild kit for your alternator - replace both rectifier and regulator.

Hope this explains what you are seeing.

 

[DSM1G90]

The reason for this is the energy in the alternator coil (inductance) needs to go somewhere and since the return path (ground wire) is broken, the energy finds a path to ground through the electronics.

Why you should NEVER disconnect the battery cable from the battery while the motor is running to check if ALT is still charging or not - blows the crap out of the alternator's regulator.

 

[Throwback23]

Well got an alternator with warrantee for cheap and got new results... everything seems good and steady at 14.5v. Thanks for the help and input everyone, this isn't the first time the autozone tester was wrong either my buddy had a charging issue a while back and sure enough we spent extra time farting around with a bad alternator that test good.

It might be worth rebuilding to have a spare or sell so who knows I might just do that...

 

[DSM1G90]

Good luck .. why everyone should stay away from AZ ..the 'wallyworld' of parts stores...

 

[Throwback23]

The alt I got wasnt a AutoZone special, it was an oem mitsu altornator... Anyways I tend to agree for the most pat... I don't mind getting plugs, fluids and filters there but your kind of hard pressed to find anything else that's useful there .

 

[DSM1G90]

I don't mind getting plugs, fluids and filters there...

Agree with this since this stuff is pretty everywhere since they do run some good sales on these items, but for more important stuff is where I head to Napa, Carquest, and the similar.

 

[Throwback23]

Update it.... I got my battery charged to eliminate it and it it passed but also wouldn't hold a charge and dropped to 12.4v from just sitting overnight out if the car. My buddy gave me a new battery and everything's good....except for that I seem to charge at 13.5v with .5ohms of resistance on the wire from the alt to battery and my buddies charges at 14v and has .2ohms of resistance on that same wire...I don't feel like .3ohms would drop half a volt and I know there's an equation but I'm in summer mode but ill see what I can do to get that resistance down...even with a new alt it just seems odd that I can't steadily get over 13.5, some think its acceotable.. I think its weird