Technical Spark when terminals connected to battery

My battery ('27 T roadster with SBC) would not hold a charge and I****umed since it was almost 4 years old it was gone so I replaced it. When I tried to connect the positive terminal to the cable, there was a visible spark (not like you get with crossed cables). I have heard that seeing a spark indicates a short somewhere in the system. Is that correct and if so where do I start trying to figure it out (I am severely auto electrical circuits challenged)? The only electrical changes that might be significant are 1) the alternator was disconnected and then re-installed to allow use of a better bracket. 2) the Mallory distributor died and was replaced with a newer model. Both jobs were done by a rod shop some distance away making taking it back impractical.

Any suggestions/info would be greatly appreciated.

 

Disconnect either battery terminal and insert a 12 volt test light between that terminal and the removed cable. The light will come on if there's a short. Now, dicsconnect things until the light goes out to find your short. Remove fuses one at a time (headlite, tail lite, dash lite, stop lite, gauges..... disconnect the alternator, etc)

 

Does not need to be a short for spark to appear, but does indicate a draw. Disconnect one item at a time to locate, or at least get a cheap VOM.

 

If there is a small spark when everything is turned off, that means something is "on".

Disconnect everything and reconnect one at a time. When the spark reappears then the last thing you connected is the one draining the battery. If you have fuses you could take them out and reinsert them one by one to do the same thing.

Mart.

 

^^^^ I type slow!!!

 

You probably don't have a "short" (short circuit) because if that were the case, it would either blow a fuse or fry the wire involved.

It sounds more like you have something drawing a current on a constant basis. That could be any one of number of electrical things on your car.

Put an ammeter between the hot post and the battery cable which should read the amount of current draw.......then start disconnecting electrical items one at a time until the current draw stops. That is your problem item.

 

Do you have a modern radio that has a memory? HRP

 

just what i was about to ask
memory has small draw at all times

 

Some modern stereos/amps have a capacitor in them that will recharge when you connect power, causing a spark, yet it won't have a continuous current draw from it, because once the capacitor charges, it draws no more current.

 

Electronics, alarm system, MSD box, etc. Lots of modern stuff draws with the key off.

 

If you have a light in the glove box or trunk make sure they are off. A misadjusted trunk switch will drain the battery and you never see it to check it.

 

Cool, all of the answers are on the same wave length and all are pretty good answers.

As a habit, I connect the + cable on neg ground systems first and then connect the neg cable.

If the spark was just a little one you most likely have a small draw somewhere in the system and that could be as simple as the interior lights being on because you had the door (s) open when you connected the battery. I was working on a used car at a dealership that was draining the battery overnight and while laying on the floorboard looking up under the dash this bright light from up in the middle of the roof hit me in the face. Someone had turned on one of the "reading" lights and left it on and it drained the battery. Sometimes it's simple little***** that messes with your mind until you figure it out.

 

Thx for all the great answers. Since the alternator was worked with ( it is a 1 wire type) I disconnected it and no longer get the spark when connecting cables. Am I good on****uming I need to pull the alternator and have it tested?

 

Check the alternator for a bad diode ... this would cause the problem you describe.

 

You may not see the spark every time. Try touching the cable to the battery about 7 times to be sure. Or, you could put a light between the battery and the cable as some of the other giys have said. That would be more reliable and easier than looking for a small spark.
Or you could swing by my house and I could troubleshoot it for you for free if you promise to give me a ride in it. I'm in Fort Worth.

 

My buddies mid-70's Blazer was doing this. Pulled fuses and did all the normal stuff. finally crawled under it and tapped on the starter solenoid and the light went out.

 

Well I chased a issue exactly like yours [the op's] for three days, finally I figured hook it up and see what/where the wires burn..Had my buddy watch behind the dash while I hooked the battery up.. In a little bit I heard a click, I asked my bud is anything burning and he said no, the cigarette lighter popped out...

 

from what I know a 1 wire alternator has no draw. it creates its own field. unless it has a bad winding.

 

Thx- a neighbor dropped by and said same thing so will ck it out.

 

A ride would be no problem but I recently moved to deep East Texas and am now 150 miles from FW

 

You will get a slight spark with a one wire alternator as the diodes absorb some electrons. An ammeter will tell you if it's actually constantly drawing current.