A short to ground. The battery can deliver a lot of current; 400 to 600 amps delivered at 12 to 13 volts The starter is the only item that normally asks for a lot of current.

Yup. In this case, it was not the weakest link. It should have indicated a roughly how much current was flowing before things fried.

It appears in this case the weakest link was the terminal for the alternator wire in the bulkhead connector. In your photo I see nothing remaining there. Several others show some damage. I don't know if that's from this event or previous heat during use. Oxidation, dirt, anything that makes it harder for the electricity to flow creates resistance which creates heat when lots of current tries to go through.


Doesn't appear to be unless you find evidence that it went toward one of those.
The ammeter itself is not a problem. Inside are two parallel paths. One small and drives the meter; the other is a big wire called the shunt. Most of the power goes through the shunt. The meter is another link and set of connections. Same deal, they must be clean and snug. As someone mentioned, it would be reasonable to check and make sure it wasn't internally damaged from the current.

edit:


If I understand correctly, first the wire from the battery to the starter relay failed.
Then after this was replaced, you were trying to figure out why it would not start. I think this can be figured out. It will help to draw out the wiring to include the voltage regulator and the ignition. I still think its likely alternator or alternator wiring related.

PS. Those Mymopar wiring diagrams didn't seem to quite match what I'm seeing in your photos. Turns out those are not factory diagrams. I have no idea where they got them from - something aftermarket like Chiltons or Mitchels I guess. If its the same as the late 60s, the real diagrams are probably in '71 Plymouth service manual (which is also on that website).

I'm gonna go (way) out on a limb & suggest that the alt main batt threaded stud internally dead shorted or near dead shorted to ground.

Bud there is not link there

Fixed it Nacho! Thanks

On the no spark question:
The disconnected wire with blue with white trace may be the Ignition 1. If so, that's why power to the coil if the key was in the Run position.

But in Start position, Ignition 2 supplies power to the coil.

This charge & start colored wiring diagram may make that clearer.

ok, I read over all the replies... from what I can remmeber here is what I have got, some of these already posted.

-The splice is original one, is the main one posted on diagrams. Reds in that splice are ign key source and BATT buss bar on fuse box, rest are headlights source and the bulkhead and ammeter sections. It is spot electrically welded and not lead welded because lead can cause somehow a resistance over a thik splice like hat

-as mentioned, the bulkhead burnt wires are alternator and batt, bot 12 gauge

-I'm still wondeting how these wires can get that damage and the fuse link which is barelly 16 gauge not to blown, even less with an engine not running.

-I can see REALLY healthy amm studs and nuts, clean and right color. I can't see any sign overheat there.

-No need to replace the full harness, just replace those wires ( 12 gauge ) and terminals ( packard 56s ). Get a new bulkhead block ( which is available around, same than E bodies ) and new engine harness plug ( also available ). Check the forward light harness plug too. Probably its stuck due the red wire overheat and plastic melt. That plug is also available. Red wire is pretty much easy to replace since is just one way from bulkhead up to ammeter. Black gets two sections... from splice up to ammeter stud and from splice up to bulkhead. Then retape the underdash harnes... piece of cake job. Packard 56 terminals are available around

-After the fix and before plug back the battery make a continuity check with ground. Will need to unplug dome light and ANY bulb which operates with batt source ( if you have map light and ign key courtesy light, unplugg them too ) since withthose bulbs conected you CAN get an ohm reading with chassis due the bulbs. Remember a Bulb is a "controlled short" what makes to glow the filament resistor, so will read a short.

-Ammeter should show a 0 or close to that Ohms reading between them and no continuity with chassis.

so... lets beging to replacing the damaged parts and then track the posible failure

Once again, I can't get a fuse link not blowing here. Even with engine running, the alt won't source the short enough, like the batt is able to, that's the reason why the fuse link is just on batt side. With an engine running selfpowered by the alt and no batt, the engine will stall with a short

Brown wire on cav 22 is ballast bypass on ign2 ( cranking )... it seems the cover just a bit melt due the black wire heat. Just clean the melted cover and apply some tape over the wire

The same with wire on cav 12 which is parking lights circuit as far I recall

I can't recall the violet traced wire loose end on pic arriving anywhere to bulkhead... maybe Horn relay source what came off from the fusebox cavity ? maybe you'll find there the terminal still into the cavity

Violet wire on cav 21 is temp sender. Seems it got some heat over the cover... same procedure, clean and tape it

A picture of the wiring at the relay may help.

Nacho while you're covering repair. Battery to starter relay should be 10 gage (or is it larger on the B-bodies?) and have insulation for engine compartments.
GPT insulation is OK inside the car, not for the engine side.
Marine is OK and has heavier wire and is tinned.
Insulation marked TXL, GXL, SXL, & TWP is OK for engine area as is battery/starter cable.

aside the wires and terminals what should be available anywhere locally at a parts shops, here the related parts to a nice fix

bulkhead
http://www.megapartsusa.com/proddetail.asp?prod=104%2DBH7074

forward light harness which maybe will get broken if you try to remove to check the red wire terminals condition
http://www.megapartsusa.com/proddetail.asp?prod=MP%2DQ8&cat=749

they had the engine harness plug too, but maybe they are out of stock at this moment ? contact them just in case. Couldn't find any other on ebay, but just in case this is a full engine bay side set:

http://www.ebay.com/itm/Wiring-Connector...nc2&vxp=mtr

You know that I made a similar thread at DC.com about how the power flows on Start and run looong time ago ? maybe at the same time I posted about the alt and wiring upgrade. will search and post


EDITING, I recall both wires being 12 gauge...

EDITING 2...10 gauge on engine bay side ( between bulkhead and fuse link ) for red one, but still 12 on cab side. I just talked about cab side because engine bay side looks still in good conditions. I don't get why 10 gauge just in that section

I copied your other diagram and will snag this one too.
Very helpful thank-you.

Here's a picture from the CJ forum of the crimper jaws for open the open barrel terminals.
http://www.jeepforum.com/forum/f8/basic-wiring-101-getting-you-started-1340134/

Some of his links are dead but the pictures are useful.
Some On-line/mail order sources for Packard or Delphi 56 terminals and connectors:
Terminal Supply Co
Waytek Wire
The Electrical Depot

I have the diagrams at my PC, but searching the thread

found it!

http://www.dodgecharger.com/forum/index.php/topic,35199.0.html

must to say, BOTH ign circuits are actually hot in both stages ( Ign1 and ign2 ) because BOTH are spliced into the ballast together, thats why the brake light on cluster dims a bit while CRANKING ( ign2 ), because this light is sourced from RUN ( ign1 ) circuit but on a decayed power through the ballast, HOWEVER I ilustrated just how it works FROM ign switch

Again thank you very much.

Nacho - I don't think I've seen one you've done with ignition circuit.
Every car is a little different so I needed to make a detailed one for mine anyway.


Maybe the larger size is to account for heat in the engine bay.
From the Battery to the Relay makes is probably because it supplies current to the relay at the starter solenoid.

kinda off, just posted it.

yeap, every car is diff. my diagrassm are of course based on 3rd gen Chargers.

and yes, definitelly I can get 10 gauge between batt and relay, but not between fuse link and bulkhead... well whatever it is the reason, the wire is there

Not certain if appropriate for this issue this late in the game, but have found this tool very helpful in shortening analysis time on some of my own tough electrical issues.

https://www.google.com/search?q=short+bu...p;client=safari

Main downside is that is designed to use with blade type fuses, but with a bit of creativity can work with older cars using glass type fuses

Best to check out reviews for further info.

Once had a very random blowing of brake light fuse on our 71 Vette,,,,had spent days sorting it out. Used this tool and found the problem in short order.

Wow! I was gone for one day and I have all these responses! Thanks for the information. I will go through all of the posts later this evening.

Today I am currently replacing the fried Red and Black wires from the harness. After those are repaired, I will move forward to replacing bulk head connectors and such.

For amusement, here is a picture of the fried Red wire from the bulk head to the ammeter taken today.

Only time I ever saw this happen was when the output wire from my alternator got up against the exhaust manifold and melted thru. That smoked a lot of wires.

I am replacing/ repairing what I can, but I haven't found the culprit yet. This was a high and dry desert car for all its life until 18 months ago when I shipped it to our new place here in Florida.

So far the only thing I can guess is those old, corroded connections became more corroded by sitting in a humid environment which led to the straw that broke the camels back.

A few weeks ago I was driving and it started backfiring and sputtering bad. It has OLD gas in the tank so I flushed the lines and put new, ethanol free gas in the tank and ran it for a while. The problem seemed to go away until I parked it. Now I am second guessing the bad gas and wondering if the electrical was starting to short at that point.

I am glad I took out the battery or it could have burned my small shop and car to the ground!

Anyway, will update later.