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Discussion Starter #1
Alright, been working on my 68 XR7 for a few months and finally got her put back together enough to start her up. Went to connect the brand new battery, last thing I needed to do, and ran in to a problem. Connected the + end first, went to connect the - end and it started sparking at the terminal. Decided to let it sit for a sec and see what happened and next thing I know I've got a bunch of smoke coming up from this little junction plug down below the battery. Here's a pic of it:
IMG00028-20110129-1529.jpg
So it looks like the middle terminal on this thing (there are 3) is fused, the plastics all melted and now I can't get it apart. Any ideas on why this is happening or how I would narrow it down to a problem area? Thanks.
 

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I have no clue as to HOW far apart you have had this car, but better start tracing your wire connections. I would look at the starter first.

I always LABEL my wires when taking things off.

You have a direct short.

Dale in Indy
 

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Make sure you have not pinched any wires with your install. Most comon is between engine and bell housing.
 

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That is the alternator harness connector, I'd say you have a problem with the alternator.
 

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Discussion Starter #5
Sorry, should have given more details. The work I was doing over the past several months was replacing oil pan gasket, tranny pan gasket, and installing headers. The only electrical part that I had to remove was the starter, which I put back and reconnected. I did change spark plugs, but I've done that many times before. It would be a bummer if it was the alternator since it's not that old, would it go bad from just sitting? Any way to check it? I was curious if it wasn't the starter motor thing that's located right next to the battery? Or any chance it could be the alternator voltage regulator?
 

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I would take a very close look at the STARTER. Is there any wires touching another contact point? Are you sure it is wire correct. It is the ONLY electrical item you worked with, then look there first.

Be like an OWL, STARE at the starter connections. FAST EYES SEE LITTLE............................

I wish you well, keep us posted, please.

Dale in Indy
 

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You may want to pull all the fuses and begin the process of ellimination if you don't see anything obvious. Note what goes where. pull them. then hook up your battery (neg first then +), you shouldn't have any sparks at this point, if you do then you likely have a dead short in some wiring somewhere, which means you need to find it before putting any fuses in. If you are ready to start installing fuses, you should be able to find any problem circuits as you put them in...it will blow if it's the correct rated fuse for the the circuit and there is an issue. At least this will let you know where to start looking.
 

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Ockham's Razor..."the simplest explanation is most likely the correct one." You may have a short in the plug itself, causing it to arc within the connector.
 

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Discussion Starter #9
A short in the connector? You mean the neg battery cable?

I spent a while just following wires today to see if there was anything obvious....but alas it wasn't meant to be that easy. My next question was going to be the best way to eliminate things but I think I'll go with Bad69Cat's idea of eliminating fuses and see what happens. My suspicion is that it is either the alternator or the alternator voltage regulator. Any way to test these things with an ohm meter to see if there is a short in them? Thanks.
 

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No I mean in the black, three prong connector you took a picture of. The prongs could easily have been arcing within the plug. This has happened to me before when I have had water in connectors or the connector wasn't plugged in far enough. Otherwise it sounds like a surge in which the fuses would have broken. Or at least that's what I could be wrong or right about ;)

I would replace the melted connector with a new one and try again. If you have more smoke and spark, then it's not that. It doesn't make sense that something else would go wrong if you haven't changed anything. Try fixing the weakest link in the system...the connector(junction plug you call).
 

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I'd try to get that connector appart if you can. It's possible they melted enough to touch each other... Also you can take your alt to a parts store and have it tested. They can tell you if it's bad or not. Sometimes the diodes go out especially if something got pinched/shorted on the output side of it. IF you have a schematic you can use your ohm meter to test the leads to ground and to each other to see if you have a short. Maybe somebody could post up one or at least which wire goes to what? I seem to have misplaced my CD but it doesn't cover 68 anyway....a good starting point anyway.
 

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The middle terminal is the alternator output. Ford changed the harness design in '70 ('69 still had it). Bad idea to have the full capability of the alternator present on a single push-together terminal.
 

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The middle terminal is the alternator output. Ford changed the harness design in '70 ('69 still had it). Bad idea to have the full capability of the alternator present on a single push-together terminal.
Yes, he's right.

If the back of the alternator is not "clocked" correctly the BATT terminal is very close to the cylinder head.
This would be the first place I would check.
 

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Discussion Starter #15
AH HA! I believe I have found the culprit. I was taking the wires off the back of the alternator, was gonna run it down to Napa to have it tested. The nut for the White stud that comes out the back (one is red, one is white, and one is the ground) just fell off, it wasn't screwed on. I went to put it back on and it wouldn't tighten. I took off the black harness thing to get a look at the stud and it is stripped...aargh. So anyone got an inexpensive fix for this? Hoping I don't have to buy an all new alternator.
 

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Discussion Starter #17
Alright, so I was able to get a different nut on the end of the stripped alternator stud...which got me set back up to try starting her up again. So before I went to hook the battery back up I double checked everything and something just didn't look right. At first I couldn't tell what it was...then it hit me...aaargh I'm a total idiot, I HAD PUT THE BATTERY BACK IN BACKWARDS! :klo: No wonder I was getting sparks and smoke. Please tell me I'm not the only dufus with a story like this. I was thinking of starting a new thread where we can share our mechanic brain fart moments, it might make me feel better :toung:

And thanks to all who chimed in here to help me figure this thing out, I really appreciate it.
 

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Well, at least you are big enough to admit to such a blunder. All is well that ends well. :beer:
 

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Hey, happens to us all.

You've probably blown the diodes in the alternator, you might want take it out and have it checked.
 
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