Went up in smoke!

In the process of breaking in the camshaft on the motor. Had it running for 30-40 minutes. Then I had sparks shooting out the top mounting bolt of the alternator bracket. A few seconds later the smaller red wire that is part of the positive battery cable terminal end decided to burn up.

Background:

I upgraded the factory 37 amp alternator to a 100 amp alternator by replacing the stator and diodes.

I was instructed to use 8 gauge wire from the horn relay to the alternator, which I did.

The wire from the battery to the horn relay is thinner (10 gauge I believe).

Will installing an 8 gauge or thicker wire from the battery to the horn relay fix the problem or is this symptomatic of another electrical demon??

Pictures of the wire below:

d1

 

I would not suspect the 10ga battery wire to be the culprit, but it now needs replacing.
Almost sounds like the alt malfunctioned.

Did you measure the output voltage of the ALT after rebuilding it?
Did you check it after the flare-up?
If it was overcharging the battery this issue could occure. I assume you are running and internal regulator? It could have failed.....

 

I did not measure the voltage either before or after. What range should it be within?

And it is a 10DN alternator, so it is externally regulated. I replaced the old Delco unit with a Wells electonic voltage regulator unit.

I did notice the voltage meter was on 14 while I was running around the motor attending to other things. So I thought I was good. The old alternator would be lucky to be over 12.


Oh, and why is the wire from the battery post of alternator going thru the horn relay. Shouldn't that wire go to the positive post of battery and then a fusible link wire going to the horn relay from there??


d1

 

between 13 and 15 ideal, 16 is max. Anything over 16 in defective and can over-current the battery.

 

How do you bench test an alternator?

 

14 is right.

I'd suspect a short somewhere - you need a lot of current to melt a wire like that, probably more than that alternator would be able to put through a non-shorted battery. If your battery is good, look for other places where a positive terminal might have touched ground.

- Eric

 

... but even then, you'd boil electrolyte and maybe warp the plates, but you wouldn't pass enough current to melt a 10ga wire.

- Eric

 

I will double check battery charge. And I will check the battery cable going to starter solenoid post to ensure that did not have the covering melt and ground out on the header.

I was leaning over the wire/battery with my timing light when this happened. So I thought the timing light had something to do with it, since it is hooked to the battery--maybe a clamp came off and touch something, but everything looked good. The clamp over the ignition wire was touching the A-arm, would that do it??

Got my adrenaline going when I had sparks shooting out of the bolt head at eye level. Good times...

 

Ohhhhhhh... The truth comes out.

You may have had something lay across something else - positive Alt. terminal to ground or Pos battery terminal to ground, for instance.
Is your timing light metal (mine is)? That could do it, too.
The high-voltage pickup to the A-arm should not be a problem.

Think about what you did and how you moved, and look for little melted spots on tools and terminals, indicating points of contact.

- Eric

 

I would suspect the alt,going from 37 amp to 100 amp proberly caused an internal short in the alt,that would explain the sparks at the mountin bolt.Where did you connect the battery ground cable?That new paint may be preventing an good electric connection for the alt.Is that a yellow crimp connector I see in the burnt wire,a poor crimp could cause risistance,which would cause heat.

 

Battery ground cable is hooked up at the engine block (behind power steering pump) and it is also hooked up to the chassis. I scraped the paint before mounting the ground cable.

Yes that is a yellow crimp connector-- never thought about that. It definitely originated at the crimp.

I cannot find any shorts or places where something might have grounded a positive terminal.

Is there a quick way to test the alternator (without the motor running) to see if there is a short/resistance in the alternator??

d1

 

Those crimp connectors are not good (solder everything!), but, unless stray strands of wire escaped from the connector and grounded out, it was not responsible for this problem. If you have enough resistance to cause heat in the crimped connector, the connector would have gotten hot, but not the rest of the wire.

- Eric

 

Sorry can't agree with that.
Around here some parts outlets have alternator tester,you just bring them the alt and they will test it for you,usually at no cost.

 

When an electric current passes through a resistive conductor, heat is generated.
That heat is generated at the location where the resistance is. It is not generated elsewhere. Heat can be transferred by conduction through the wire, but that is not what you're looking at here. The entire wire acted as the resistor because the current was too great, it heated up and melted the insulation.
This wasn't the fault of resistance in a single connector.

- Eric

 

maybe the wire insulation near the conector melted off and the wire shorted to ground causing the wire to burn up.hard to say without a close look.still I wonder what caused the sparkes at the alt bolt.

 

Alt isn't grounded good enough at the bolt where sparks occured. Add a ground wire to the alt. High resistance at the crimp caused the wire to melt, Solder the crimp connection.

 

I give up.

 

I grounded the alternator with a separate wire. I hooked up a 12 ga fusible link from the postive battery post to the horn relay.

As soon as I touched the negative battery post-the fusible link went up like I just torched off a firework. Smoke, flames etc. BTW the wire covering when it melts rapidly sprays its liquid plastic mess everywhere.

I checked all my connections from the battery and nothing looks out of the ordinary. The battery has a full charge. So, I am going to tear apart the alternator and see if something happened inside. Not sure where else to look.

Have to wait for the smoke to clear in the garage...

d1

 

Check around the horn relay and surroundings.
You've got a dead short somewhere.

--- oh, and obviously, disconnect the positive alternator wire and see if you've still got a short...
- Eric

 

Definatley a dead short. If in the alt and it is a 10 DN be sure to check the insulators it is easy to mess up the condenser insulators. There is one between the rectifier plate and case that likes to sneak out when putting them back together. Check the condenser insulator on top too. Be sure it is between the condensor lead and the screw.

 

Ok took alternator apart. There is no insulator in between the rectifier plated and the case as it relates to the capacitor (I think this is the same thing you are talking about, when you refer to condensor) . No idea where it went, so can I use a rubber or plastic washer in lieu of whatever the original insulators are made out of.

Can you explain why this missing insulator would cause a short? I had the plastic insulator that inserts in from the top of the rectifier installed. I assume that this was not long enough to prevent the short, I thought it went all the way through to the case. Now I know different. Not too savvy when it comes to alternators. I thought I did well upgrading it, but obviously I was missing a part.

 

get another alternator before you lose the car and the garage!

 

I kind of have to agree, even though I'm the first guy to say, "Just do it yourself!"

If you're "Not too savvy when it comes to alternators," and you're not sure why a missing insulator would cause a short, I'd keep the current alternator to play with and learn from and get another one for the car, until you're confident of your skills.

We could discuss and advise about how to fix this one all day, but I, for one, would not feel confident that my advice would be properly calibrated to your knowledge level, and that the final result would be correct. If you go over the alternator, the exploded views, and the parts lists, and read a couple of descriptions of how it works, I am certain you can get to the point where this will be a "no brainer" for you, but I just don't feel good about telling you to "fudge" it with improvised parts at this point.

No offense intended, and I hope none taken.

- Eric

 

Stellar you are my new hero! Put the alternator back together in the order you described above and guess what no smoke or fire! Yeah, buddy!

So, now for the somewhat bad news. The voltage gauge read at 12 and the GEN dashlight stays on all the time (when motor running).

So did I fry the voltage regulator when the dead short happened?

What wire/circuit is dedicated for the dummy light?

d1

 

Threw on the old voltage regulator and the GEN light still stayed on when the motor was running and the voltage gauge read the same 12 volts. The only difference is the GEN light was brighter (at least twice as bright), with the key on or motor running.

d1

 

After some reading (as Eric recommended above), the GEN light being on indicates a difference in the voltage between what the battery is charged at vs. what the alternator is supplying. Well, since my alternator is supply 0 volts, then it looks like my diodes are fried.

So, anyone know where I can get some Heavy Duty diodes for a 10DN alternator. I a bought another alternator as a back up, but need to get this one up and running as well.

d1

 

I can supply you with what ever you need for the alt. The original diodes are rated at 25 amp. 35 amp diodes should be fine for the 100 amp stator. The insulator that was missing keeps the pos rectifier plate which is hot from touching the case which is ground. I hope you got the other insulators in correct. You said you put in new diodes when you changed the stator. Did you press in new diodes or change the whole plate and case? The holes for the diodes can become slightly enlarged if not done correctly and even then may become worn. The diodes must be a tight fit. If you need help or parts let me know I can help. mark

 

Thanks Mark, good info to know, I will PM you about getting the 35 amp diodes. I did press in the new diodes, it was a PITA due to the tight fit. I guess there is a special tool to assist in this process, which I did not have.

Thanks again
Shaun