Sooooo, I hooked the positive battery cable up and there was a big arc and a rather loud "pop" up front somewhere.

A little background info... I'm mid-restoration and have installed the new wiring harnesses but most every connection has nothing to hook up to as I haven't installed anything but the engine and transmission. I'm running an MSD ignition. I have the voltage regulator, horn relay, temp sensor, starter, and alternator hooked up. Nothing else is hooked up. I've started this car dozens of times this way. Today I decided to "tidy" up some of the wires in the engine bay. The only thing I did differently was hook up the blower motor hot and ground and put the stock coil wires (one connection of two wires) to the positive on the coil. Then I touched the positive battery to hook it back up and the arc happened and the pop from up front somewhere. The MSD instructions say that the hot wire from the MSD box is the only wire that should be connected to the coil positive but I thought, in my haste, that the stock coil positive wire might need to be hooked up for some reason. I now know that wire is hot when the switch is on so I disconnected it per the MSD instructions. I'm very concerned about that pop noise. The only two things I have hooked up really are the horn relay and the voltage regulator. How do I test those? One note is that in previous starts, when I hook up the positive battery cable I hear a "buzz" when I put the key in until I turn it to the on position. After this incident, there's no longer a "buzz". Does that noise come from the horn relay? I undid everything I hooked up today and started it. Starts fine and no arc at the battery post. But I'd really like to know what I broke before I get too much further. Thanks in advance, Jason

Almost forgot the details... 1968 coupe, 327, TH400, with A/C and power windows.

 

Sorry all, I meant to post this in the tech section.

 

Not sure about your electrical problem, but I was taught to always connect the negative cable last and disconnect it first.
Just a tip, that's all I got.

 

Hi 13,
The key buzzer IS part of the horn relay.
There are 3 'fusible links' that are part of the engine compartment wiring...one at the horn relay, one near the wiper motor, and one at the starter.
You might begin by checking the one at the horn relay.
Here's the 'fusible link' at the horn relay on a 71. It may be 'burned' in to two pieces or just look 'distorted' if the circuit it is protecting was overloaded.
Regards,
Alan

 

Make sure your ground from the blower motor is connected to ground. Common error that the ground wire ends up hot at starter.
You could disconnect the wires (sounds like only a few) and then check with voltmeter to see what is not working that was before

 

The loud pop, and arc is an indicator of a short circuit. Is anything shorted to ground?

 

The power for your car goes from the battery to the starter then from the starter to the horn relay and out from there. There's a fusible link at the starter, the wiper motor area and the horn relay. I'll post a pic later of the harness. You should turn the key to run and see if you have power at the horn relay. If not check for melted links. I would also check you lights, horn and wipers. see what actually works.

Your other connection's at the starter are your ignition wire, purple, it works, yellow is the power to the coil when starting, and black is ground. At the coil, white is power to the coil after you release the key switch

 

the 2 lines are which red wire goes where. The long red on connects to the horn relay





The single long red wire goes to the horn relay, it should be a horseshoe connector. You should
1. disconnect your battery, 2. disconnect this red power at the starter 3. disconnect the red wires at to horn relay 4. use a meter to check for 0 ohms from one end of that wire to the other.



Yellow and white connected to horse shoe is the coil positive
Black is wiper housing ground
Yellow bullet is washerfluid
Blue bullet is washer fluid
Y/B/G is from wiper switch, wiper door relay and power from the fuse panel
Red and black plug is power/ motor ground
Fat black plug is interlock door switch

 

 

This fusible link goes to the ammeter

 

This is the fusible link that might have blown at your starter

 

WOW, thank you so much to all for this information. What exactly does a fusible link consist of? If I find a blown fusible link, how do I go about repairing it? Thanks again.

 

Its a weak link built into the harness that melts before the rest of the harness. You can buy replacements to splice in or you could hardwire in a breaker if it is blown.

 

let us know where you still have power. If there is no power at the buss bar on the relay then its probably the fusible link. Does the horn work, lights? Is your ammeter deflecting at all when you turn accesories on and off? Is your alternator making power?

 

Hi 13,
"What exactly does a fusible link consist of?"

A 'fusible link' typically consists of a wire that is 4 gauges SMALLER than the wire it is protecting.
So a circuit with 10 gauge wire would use a short 14 gauge length of wire as a fusible link.
The little black rubber 'barrels' cover/protect the splices that are required to connect the fusible link in place.
Regards,
Alan

 

But do you know why they say to do it that way??

So you don’t touch your wrench to the hot battery post and a “grounded” component or body panel. Doesn’t really appply to our plastic panel cars but its always a good practice.

 

Thanks again for all the help. Rescue Rogers, I don't have any of the things you said to check hooked up in the car. Basically just what I takes to make the motor run. I tested the horn relay and it functioned properly with the exception of the buzzer only barely working about 30% of the time. Most of the time it wouldn't buzz unless I tapped it. I went ahead and replaced the horn relay and the voltage regulator just to be safe as I don't want possible issues as I proceed putting this thing back together. Starts good, runs good, 14+Volts when running at the battery and no spark or noise when I hook the battery up. I also disconnected the few things I had connected when I first posted. Two variables in this equation that I discovered along the way. My loose wiring harness in the cabin has many "ends", for a lack of a better term, just laying on the floor. The floor has foil covered insulating material on it. I have since secured any loose wire ends with tape. Also, The metallic spark plug wire shielding I put on to protect the wires from header heat were laying on top of the positive battery cable at the top of the starter. I've corrected that as well. I don't know if the horn relay or voltage regulator could have made that "pop" sound that I heard but I've replaced them just incase. Any thoughts? Oh, and the MSD system is working just fine.

 

From the description of loose wires and metal near the battery connection, one of those could have been the pop. That's good news, you could be all set. if the horn buzzes then it's getting power which means the fusible link didn't fry.

Keep us posted. Post Pics of your vetted as well

 

Keep us posted. Post Pics of your vetted as well[/QUOTE]

Will do! It's been a couple of years since I updated any of my threads. Got the last of 4 girls off to college, sold the house and traveled Europe for a year. Bought a house last August, just finished the remodel and made a comfortable home for the Vet in the garage. So now it's time to start posting again. I'll post some pics here as requested, then I really should bring some of my other "follow alongs" up to date. I might do a thread in the Paint and Body on my workshop/paint booth. We'll see. Thanks again and here ya go...







And here's a few of the third bay of my garage. I've made it so I can keep the dust and paint mess out of the rest of the garage. I used a lot of windows and a glass slider because I didn't want to feel like I'm in a cave. There's 6 intake filters to bring in clean air when I paint and an exhaust wall that uses one of the natural framed 24" wall cavities vent the fumes through filters, pulled by a 5000cfm fan mounted outside. The compressor is outside in a shed and the air plumbing is run through the attic and down the walls. I have a Devillbiss dry air filter and then a larger desiccant filter that I made on the cheap from a hack I found on line. Anyways, here's some pics and if anyone has questions, let me know.

 

WOW, I'm officailly jealous!!!!