The Stovebolt Site Forums The Shop Area The Electrical Bay How bad did I mess things up?

Hello. Newbie here. Just bought a 1952 3100 a couple of weeks ago. Hasn't run in years. Has been converted to 12 volt. Battery that was in the truck was from 2002, and corroded pretty bad.

We (son and I) removed the old one, cleaned up the connectors and attempted to connect the new battery.

Now, before proceeding, when we disconnected the old battery, the "red" cables were on the negative side of the battery and the black on the positive. Thought that odd, but just assumed someone wasn't paying attention and since the battery was dead, nothing came of it.

Of course, using what little mechanical skill I have, I connected red to positive and black to negative. This was soon followed by a sparking sound somewhere in the engine bay accompanied by smoking wires in several places. I quickly disconnected the battery.

So, what damage did I do? Assuming that black should have been positive and red negative, was this just an error in how the truck was wired during the conversion? I'll post some pics of the battery, etc in the morning when there is more light.

Thanks in advance.

Ron

Regardless of the color of the cable insulation, the positive (+) terminal of the battery should have been connected to the starter, and the negative (-) post should have been connected to the frame or engine block. Chances are that the positive smoke check was the alternator shorting out due to the polarity reversal of the six diodes that convert the AC current produced by the alternator into DC suitable to charge the battery. Check the big wire that's connected to the back of the alternator- - - -I'll bet it's burned, and the alternator windings will have a definite odor of barbecue! Other than the alternator and its associated wiring, there might be a problem with the radio, if it's been converted to a modern solid-state type with a constant-voltage "keep-alive" circuit for the memory. Sometimes there's a low-current fuse in the back of the radio that will blow in case of reversed polarity. Good luck!
Jerry

As far I as I know the Chevy trucks were always negative ground. GMC trucks could be either....
About have to start doing some checking to find where the problem is.....
Might have been more of an issue with the truck being 6 volt and installing a 12 volt battery.... The gas gauge, lights, generator/regulator, ignition coil, heater motor are all ,originally 6 volt, unless someone has converted it to 12 volt.
John

Here is a pic

I should have payed more attention when we took of the cables originally and noticed they were "flipped". Just honestly didn't know to look.

The positive/negative discussion is going on in two threads.

Sorry about that. I was informed to ask questions in the right area. Somehow, I got my wires crossed.

No problem - parallel discussions are quite common. It is sometimes interesting to watch them diverge, but more often the posts are cumulatively informative.

Wired as shown in the picture it looks like if you put
that red cable on the battery you simply had a direct
short from the positive side of the battery to the
negative. I think the PO was using the red cable as a
ground cable.

Here's a picture of the standard hookup as done at the fatory on
all AD trucks:
http://www.pbase.com/dennygraham/image/121749014
Here's how your battery should be hooked up:
http://www.pbase.com/dennygraham/image/153983976

I'd clean that up by taking the red cable out and throwing it
into the corner of the garage. The battery should have a short
ground strap from it's negative post down to the frame right
behind the battery box. From the positive post of the battery
that black cable should thread it's way directly to the post on
the starter switch. The short ground strap bolted to the back
of the engine (the bell housing) returns to the battery thru
the frame. When the normally open spring loaded button on the
starter switch is depressed it completes the circuit, that's all
there is to the starter circuit.
I would first start by removing the other wires from the starter
switch to see if the start circuit alone is working properly.
Then go from there to trouble shoot the rest of it.
dg

Thank you!. Follow up question. The battery is currently located in the engine compartment, up against the firewall on the passenger side. Not sure why it would have been relocated there. I'll have to look to see what kind of condition the compartment is in under the floor. Should I move it back there? Since it's a 12 volt, will it fit in the floor compartment? If not, since the battery is sitting up higher than the frame, connecting the negative side using the strap is not possible. I'll get a few pictures of the setup in a little while.

A braided strap is totally unnecessary unless you're going for some sort of show-winning concours restoration. With a 12 volt system, that's impossible anyway. Funny thing about copper wire- - - -no matter whether you shape it into a flat braided strap or a plastic-insulated cable, it still carries current! Just reconnect the cables, red to the insulated post on the starter, black to any convenient ground such as one of the bellhousing attaching bolts, or the starter-to-block attaching bolts, etc. Then run a flat braided ground strap OR a heavy wire connection from the block to the body or the frame (or both) to assure the lights and other accessories get a good ground path. The trick is getting the current back to the battery with the least amount of resistance. Once the main cables are sorted out, then track down the burned/damaged wiring and repair it one circuit at a time.

You're almost certain to have to replace the alternator- - - -if the battery was connected backwards for more than a couple of seconds, it's toast! There are 12 volt batteries made that will fit the original under the floor box, but you'll probably need to install different-length cables if you go back to that location.
Jerry

Here are some pics of the battery, the alternator, and some of the wiring that was smoking...

Alternator

Battery

area of some of the smoking wires

other side of firewall

Am I seeing lots of original cloth covered wires? That would scare me, as they don't age well, leaving bare wires in bad places. Might be time to rewire the entire truck.

I'm with 52 Carl. I picked up my truck this Sept. the wiring was original. Was original ! It took me about 14 hours to put in a new harness, excluding the dome light, that's a a few more hours and in progress since the headlings need to come out and I'm adding a shoulder harness while it apart. I ordered a standard kit for around 150 but added another $150 or or so in new grommets, turn signals,front parking lamp sockets and terminals for headlamps. I also bought the wire harness clips and changed those as necessary

Since this was converted to 12 volt, what differences are there in the wiring harnesses?

The original wiring harness had natural rubber wire insulation with a braided fabric covering. The insulation deteriorates and flakes away, leaving a huge potential for shorts and fires- - - -as you've already experienced. Patching on the old wiring is like giving a patient with a brain tumor an aspirin for his headache- - - -treating the symptoms, not the cause of the problem.
Jerry

If you are asking what new harness to order, either 6 or 12 volt will work for 12 volt. 12 volt harness will be less expensive. I stated my answer this way in case you find a new harness at a swap meet.
Carl

Regarding the relocation of the battery, it was probably done for convenience. You can locate it wherever you prefer. As mentioned, you may need to get longer cables if you put it back under the floor.

Battery location arguments - 12 volt conversion

Reasons not to move battery form original position

It's original
It's original
Will clutter up the firewall
Have to find/make a battery holder.

Reasons to move

A limited number of 12V batteries will fit in original holder, just bought one, I think type 25 and 35 and maybe 1 more.

Don't have to roll up rug every time you check the water (unless you use an Optima or similar).

Unless it is a show truck, they should all be wires - battery ground wire to bell housing, straps from bell housing to frame and cab.