I have my 66 chevelle going now but there seems to be a dead short somewhere. When there is nothing on and you remove the positive cable it causes a small arc. What would be the best way to track it down?

If you are disconnecting the pos battery cable first, then a spark can be expected. Disconnect the neg cable first ... when reconnecting, attach the neg cable last ... If you are experiencing other symptoms, please post back with more info describing your problem ...

If there is a spark there is current draw. Use a test light, you can make one or buy one. Use a side marker of tail light with the connector. Disconnect the + battery cable and hook the two wires from the the light between the battery terminal and the cable. Start pulling fuses and disconnecting wires until the light goes out. When the light goes out you found the short.

Not hard just takes some time. Not positive on a 66 but i believe if you disconnect the wire on the horn relay, the one that goes to the junction block on the firewall, that will disconnect everything inside the car. If the light goes out it's inside, if not then it's probably outside, under the hood etc.

It sounds like a small current drain and not a bad short (a bad short would really arc) or it could be a capacitor charging up.
Make sure it's not something stupid like the door being open and the dome light trying to come on or even a mercury switched underhood hood light. Verify the glove box light is out and also the brake light switch is adjusted properly.
If you have a digital radio then you will have this slight arcing or if you have a stereo power amplifier it too will cause an arcing when connecting the battery up. By disconnecting the memory wire on it then the arcing should stop. If not there is more than one thing causing the arcing. It could also be the alternator.
Jim

A small arc is perfectly normal on 95% of the cars on the road. Anything that requires B+ all the time like for memory or anything still running points will have some discharge during disconnect/re-connect of the the battery.

The neg last/neg first theory is an old wives tale, both the neg and pos cables will have discharge when there is something drawing on the system. Try hitting a 12v system with 24v for a jump start for real spark show.

I guess the problem is that I was only disconnecting the pos. cable and when I would go to reconnect it I would get the spark. It is a very little arc so I'll check it out tomorrow. Thanks Guys.

The "dead short" is the a typical backyard mechanics way of explaining any and all electrical problems. A "dead short" would cause your wiring harness to burn up so it would be easy to find...that's if you were able to save the car.. If you're lucky, a "dead short" could also just immediately blow a fuse any time you replace it and the fuse will have saved the harness and likely the vehicle.

Your little arc sounds like an accessory that uses constant battery power (anything with a clock or memory) or a light that is left on somewhere in the vehicle. It could also be in the alternator or regulator so you could unplug them and see if it goes away.

It does not matter which cable you disconnect or in what order you will still get a spark if there is a reason to get one. The reason to disconnect the negative cable first and connect it last is for safety when using a wrench on the battery terminals. It just removes some possibility for error. If the negative cable is connected and you are using a wrench on the positive cable it's possible to arc the wrench between the positive cable and some part of the body of the vehicle (fender, battery tray, rad, battery hold down etc) causing a big arc and possibly a battery explosion.

Peter

I don't know if it's a wives tale or not, but certainly it has been my observation that anytime you connect the positive side of a circuit last, it tends to create a greater spark activity than connecting the ground side last. Certainly Peter is correct in his comments about wrenches and causing big arcs ... Mainly, I was of the opinion that geg was seeing was probably "normal" activity, but I didn't think, and still don't think that disconnecting the + first is the best way to proceeed. I guess it is just etched in my brain that connecting/disconnecting + side of a circuit create greater spark activity than connecting/disconnecting the - side. Sorry if I created any confusion .... I'll Be Back !

There should be no spark.

It is not normal unless something is "on"

Peter is correct, it doesn't matter which cable is connected/disconnected first/last except to keep from having a BIG spark if you bump the wrench on something when doing it.

I tried the disconnect of the neg. first and then the pos. When I reconnect the cables I connected the Pos first and then the Neg and got NO arc. THANKS FOR ALL THE INPUT and if I experience further trouble I'll be baaack>

Dean, without knowing positively that there are no accessories that draw (like 95% of the cars on the road) with the key off it would be impossible to make that statement. Even something as small as an aftermarket radio will draw with the key off (radio presets and clock memory). Normal key off draw in today’s vehicles is about 100Ma, enough to create a quite an arc especially since the initial "kick" when providing power to these components jumps to over an amp in some cases.

Dean, without knowing positively that there are no accessories that draw (like 95% of the cars on the road) with the key off it would be impossible to make that statement. Even something as small as an aftermarket radio will draw with the key off (radio presets and clock memory). Normal key off draw in today’s vehicles is about 100Ma, enough to create a quite an arc especially since the initial "kick" when providing power to these components jumps to over an amp in some cases.

True Denny but the question was about a 66 Chevelle, not 95% of the cars on the road or today's vehicles.

Of course I'm ASSUMING (we all know what that does) a normal 66 Chevelle but good point, it COULD have a more modern after market raido with a constant draw.

I think I read somewhere that .4 amp draw is acceptable however I don't think that is enough to make much of a spark is it?