Alternator started sparking

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John Collins

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I have a 1973 Dodge Dart Sport with a MSD 6a digital ignition, blaster coil, MSD distributor and unknown after market wiring harness. I recently had issues getting power to my ignition and it also wouldn’t crank. After double checking wiring and cleaning the posts on the battery, it started working again. Fast forward a month of it sitting over the holidays and it won’t crank again. I’m guessing it’s the NSS, but I’m not certain because my floor jack decided to stop working yesterday, so I haven’t been able to check. I can start my car by jumping it at the starter relay though. After letting it idle for a couple minutes yesterday, I started to advance the timing a bit and my alternator starting sparking inside of the cage. I don’t know if the two are related. The wiring on the alternator seems fine. No burnt or melted wires. Any insight would be appreciated. Thank you in advance.
 
I would not think so. There's only one answer. Remove it and tear it down and inspect it. You have a service manual? Go over to Mymopar and download one free

This COULD be dangerous, as a short in the main charging circuit could pop the main fuse link WHICH IS POOR LAST DITCH protection, and/ or burn up some wiring.
 
AND NOW another annoying story from the old days

In the early 70's, stationed at NAS Miramar, San Diego, some girls had ploughed into the rear of the 70 440-6 RR and it was in the body shop. I had a junk--bald-tire loaner Valiant from "McCune Chrysler Plymouth" in National city. Even in San Diego, it gets "cool" once in awhile. I was getting off work near 7AM and had gone out and started the loaner. The Chief came in a couple minutes later, doing his kintted-eyebrows "Columbo" look. "Say, I just have ONE question? Is it supposed to be SMOKING AND SQUEELING?"

So I went out and shut it off, and for some reason took a rag and loosened the belt, and tried to move the alternator pulley. This was the older "round back" with individual diodes. Turns out a diode had FALLEN DOWN INSIDE the alternator but the WIRE WAS STILL connected. When I moved the pulley the DIODE SHORTED into the case and I got to sit there and watch the underhood harness go FAAAXXXXXAXXZZZZZZZZZZZZZZZZZZZZZZLLLLLLLLLLLEEEEEEEESSSSSFFFFFFFFFFFFTTTTTTTTTTtttttttttttttttttttttttttttttttt!!!!!!!!!!!!!!!!!!!!!!!!!!! and then the fuse link blew!!!

So I called the dealer and told them "send a wrecker and a second loaner car, the wiring burned up

So they sent the green card holder in a junk pickup truck with about a dozen dead batteries and 1/2 a pair of jumper cables. He looked and me and said "YOU ARE GOING TO NEED another loaner car!!! YOUR HARNESS is burned up!!!!!

(It's about 25 mi. one way from Miramar to the dealer in National City so I got to wait awhile for the "return trip")
 
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Replace alternator immediately .. My Alt shorted out and thank god for fuseable link or my car could have burned up.. sounds to me like yours may have melted also ..
 
If this is a small block with Distributor in the rear you may have shorted wiring while turning Distributor.
 
It is... It’s an LA 360. Just did a visual check of the harness and it looks fine, but that is not saying much. I’m a pretty incompetent when it comes to wiring, but slowly learning. How would I test if the wiring shorted out? Thank you!

I do have a manual 67Dart273. I’m going to strip it down and see what’s up with it. I’ve never opened one up, so I’m kind of looking forward to it. Thank you!
 
One thing that used to happen to these is that either the housing comes loose, or the "step" in the housing where the stator sits becomes worn from loose/ vibration, and the stator either vibrates and moves or in bad cases the rotor can rub. In any case the vibration can loosen the winding which begin vibrating and rubbing against each other. Then the insulation wears off and the turns short together. I've seen this in darkness, looks like a mini lightning storm inside.
 
One thing that used to happen to these is that either the housing comes loose, or the "step" in the housing where the stator sits becomes worn from loose/ vibration, and the stator either vibrates and moves or in bad cases the rotor can rub. In any case the vibration can loosen the winding which begin vibrating and rubbing against each other. Then the insulation wears off and the turns short together. I've seen this in darkness, looks like a mini lightning storm inside.

Thank you! Is there any way of trouble shooting this with a volt meter, before cutting open the harness?

It was dark when the alternator started sparking... It was pretty cool looking, I must admit. Scared the **** out of me though and I quickly turned the car off.
 
Get yourself plenty of light & start inspecting the harness. If you shorted something bad enough, you might see the melted taped & plastic insulation. If it were mine, I'd strip all of the tape off & inspect each wire from end to end & any connections there within. We've had electrical shorts on the race car, due to vibration & hard use. Every year, I strip off the tape & look for potential problems. By doing this, we haven't had anymore short circuits in the past 10-11 years.
 
I have a 74 Duster 318 and looked at the wire bundle behind dist.. When you turned to change timing, the clips that hold cap on may have disturbed all the wiring back there. If alt. is no longer sparking maybe you could move harness to see if it effects alt. again.
 
Might be that the brushes have warn to the point of no return and the spring is riding on the comuter (sp?)
 
A few of us have posted pictures showing various stages of disassembly.
'73 should have a squareback which is easy to replace parts on.
It is... It’s an LA 360. Just did a visual check of the harness and it looks fine, but that is not saying much. I’m a pretty incompetent when it comes to wiring, but slowly learning. How would I test if the wiring shorted out? Thank you!

The BIG danger to the harness is when the output portion of the alternator shorts to ground. When that happens the battery positive is shorted to ground.
eek-gif.gif

Illustrated as example 2 here: Fusible Links in Charging Systems with Ammeter

Basic test would be disconnect the battery. Then check for continuity between the output stud and the alternator case.
When you open it up you can check for continuity between the stator windings and the case, as well as each other.

Like Dana wrote, check the brushes. Before opening the halves, see how much play there is in the rotor.

or the sparking could be enough insulation is missing from windings...
 
Thank you very much y’all! I’m going to start by opening up the harness and start inspecting every wire. After I find and fix the faulty wiring, I’m going to open up the alternator and see what i can see. I appreciate all the responses! I’ll post back in a couple days with an update on how it went.
 
Be sure to check all of the connections at the bulkhead connector between the engine bay & interior for corrosion &/or shorts.
 
That's in fact where to start. The connections are the weak locations. If they're good, then there is no reason to unwrap the harnesses.
I'd start with the alternator actually. If you can find the reason for the sparks, then you'll know where to look at for possible wiring issues, if any.
 
I checked the brushes and they were fine, cracked open the alternator and everything looked “normal”, checked my wiring and everything was “fine”... except my grounds. I took all grounds off and my main ground on my block was over paint and my starter relay was loose on the fender. I cleaned all the paint off the engine at the connection and put in some bolts and nuts to secure the relay. It starts like a champ now and my alternator is working without sparks. Thank you guys for all the help! I’ve learned so much from this site!
 
More electrical issues. Since my last post, I’ve fully unwrapped the wiring harness and found a mess. I had a power drop of .3 at the alternator and found that there were a few fused wires and burnt connections. I rewired all the bad/fused wiring I found, which was every wire in the middle bulkhead. The 8 prong connector under the dash, that has the ignition wiring had a fried terminal. When trying to remove the male end, the 8 prong connector cracked in a couple places, so I fully disassembled it and mated each side to each other and wrapped each connection in electric tape(temporary) and replaced the one faulty wire connection which was the dark blue ignition run wire. I was still having a drop of .3 at the alternator. I then ran a new blue ignition run wire that bypasses the bulkhead to test. Now, the MSD box light doesn’t come on and the engine won’t fire. I have direct connections to the positive and negative battery terminals from the box. I’ve gone through and cleaned up the bulkhead connections. At this point, I think I’m going to hardwire all the middle bulkhead wires and drill out a hole to feed them through. Or is it better to just get a whole new harness and fully rewire?!? I really don’t want to spend another $500. I’m lost. Lol. I’ve searched a bunch of threads here and watched enough YouTube videos to think I know what I’m doing, but before I start getting into more trouble, I thought I’d ask for another round of advice.
 
Well there are about 5 answers to this, none of which are right or wrong. "It's up to you." You surely must have learned the system somewhat by now, and have some idea what you are doing, and what "is not" wrong

You can fix what you have

But a used harness and either use/ repair it or use parts of it to repair yours

Buy a new "repop harness

Or buy an aftermarket "universal" harness and start over

So far as MSD, if you have not, go to their website and paw around. Somewhere in the MSD sit/ destructions are some troubleshooting tips. Things like you can use the white breaker points wire to trigger the box to check it, etc. Make sure the white is NOT grounded.

I would "hot" wire the MSD to check it. Always suspect the distributor connector Make sure it has ground (big black) and that big red and small red are hooked to battery. Disconnect dist, and ground/ unground white to check for spark. Then check dist pickup connections and dist. itself
 
Well there are about 5 answers to this, none of which are right or wrong. "It's up to you." You surely must have learned the system somewhat by now, and have some idea what you are doing, and what "is not" wrong

You can fix what you have

But a used harness and either use/ repair it or use parts of it to repair yours

Buy a new "repop harness

Or buy an aftermarket "universal" harness and start over

So far as MSD, if you have not, go to their website and paw around. Somewhere in the MSD sit/ destructions are some troubleshooting tips. Things like you can use the white breaker points wire to trigger the box to check it, etc. Make sure the white is NOT grounded.

I would "hot" wire the MSD to check it. Always suspect the distributor connector Make sure it has ground (big black) and that big red and small red are hooked to battery. Disconnect dist, and ground/ unground white to check for spark. Then check dist pickup connections and dist. itself

Thank you! Your name came up in a Facebook thread and I thought to myself, I should ask for help because I’m struggling and you are. I really appreciate it! I’ve read so many of your posts on electrical problems and you’ve always had incredible advice, so much so that you’re brought up on threads outside of FABO.

I have a partial harness from a 72 dart that I’m going to break down and try and make work. As far as connecting the middle wiring directly and bypassing the middle bulkhead head connector and keeping the two outside bulkheads intact... That should be fine, right? I’m feeling gun shy. Thanks again!
 
You can get the plastic bulkhead connectors and move all your wires over.
That way your keeping it as stock as possible, and thus easier to work on.

I would not go with a aftermarket "universal" harness. Aftermarket stock would be good
 
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You can get the plastic bulkhead connectors and move all your wires over.
That way your keeping it as stock as possible, and thus easier to work on.

I would not go with a aftermarket "universal" harness. Aftermarket stock would be good

Are your saying to replicate the bulkhead connectors elsewhere? I was hoping to eliminate one of the bulkhead connectors and use marine grade heat shrink “butt” connectors and feed the wires through a hole where middle connector would be. Obliviously, I’ll feed the wires through the hole first and then connect them.

Thank you on the Universal harness advice. They look like a lot of fun though. Just kidding. What Stock aftermarket replacement would you suggest? Just in case I can’t get this thing safe and road worthy with my scab approach.
 
I could not suggest one over another, but the more OEM it is the easier it will be to wire.

Regarding the bulkhead connector, most of the connections are not taxed only the main feed and battery feed are. Those two you could bypass around the bulkhead if you plan on new high current electrical devices being added to the car.

If just stock not needed,

Tighten up the metal contacts, replace any that are bad, a d you are good to go for another 50 years
 
I tested my connections and found that I did a poor job rewiring the blue wire. I’m getting power to the MSD box again. I still have the .3 loss with direct connection. When I unplug the blue ignition on wire, the loss goes away. I took apart the steering column and checked out the wiring a while back and it looked fine. Where could this gremlin be hiding? Another possible clue... When I turn the lights on with the engine off, there’s a big drop on the ammeter gauge. All lights work, but the driver side front marker light is out.
 
Are you trying to track down a .3v voltage drop?

Maybe your meter is not accurate?
 
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