Installing new battery turns into fryer fire

[Nebulas die]

Hello datsun community,

Long time lurker and first time poster. I recently purchased a 1977 280z and it has been sitting at home for a couple of months. When I tried to start the car, the engine sounded like it was trying to turn but not enough electricity was coming from the battery. I tested and the battery fail. Today, I bought a new battery and plugged everything back in. Immediately, one of the wires starts to glow red hot. Fire ensued. I quickly removed the battery and it seems like I made a mistake? I don't know where to start.. Can you guys give me a hint?

[SteveJ]

You probably installed the battery with the poles reversed. If you are lucky, you only fried the fusible links.

Step 1: Buy new fusible links. (Remember there is a 5th link not in this shot.)

Step 2: Replace the fusible links.

Step 3: Use an ohmmeter to figure out which battery cable is the negative. It will be the one that has about 1 ohm resistance to the chassis ground.

Step 4: Mark the negative cable so you remember which one it is. A stripe of colored electrical tape would work nicely for that.

Step 5: While having a fire extinguisher close at hand, re-install the battery. Put the positive cable on the positive terminal of the battery. Put the negative cable on the negative terminal of the battery.

Step 6: Figure out if you burned up anything else.

[Nebulas die]

Thank you SteveJ.

I am going to do as listed and report if there is another fire.

I am sure I placed the poles in the right order. However, when I placed the positive pole on first and then the negative pole , I get these small sparks or visible currents before the negative pole just as it touches the negative terminal. Does this sound correct or even safe?

[S30Driver]

The big heavy cable running from the starter solenoid to the battery (held on with a nut)... is it on the battery terminal closest to the starter or the one under the inspection cover?

It should go the the positive battery terminal.

If you don't have the covers for the fusible links, I would invest in them, they are cheap.

[Mark Maras]

It's possible there is a short circuit somewhere in the system if it's not reversed polarity during the install. Which wire was glowing & what caught fire. Before hooking up the battery, I would pull all the fuses, turn all switches off. & check the spark at the battery with a quick tap of the cable on the post. Everything OK? Then proceed to plug fuses in one at a time & recheck the spark at the battery. Keep in mind all these spark tests are shade tree mechanics at best. A multi-meter is still the best way to attack this problem. Also look carefully at the fuse block and connecting wires for heat damage.

[Zed Head]

The battery was installed correctly and things worked right before you removed the battery and put a new one in, so odds are you connected the new one backward. I have seen batteries with the positive and negative terminals reversed. If you didn't match the - sign on the battery with the cable that connects to a starter mounting bolt, and the + sign with the cable that connects to the starter solenoid (where the other wires also connect) then you probably just got your poles switched.

Find the + and the - on the battery top and make sure that they're connected correctly.

[Bonzi Lon]

Reversing the cables happened to me & the 73 once, fried the link. That is when I noticed both battery cable ends were black. When I picked up the new fuze I also got a RED battery cable the proper length. That mistake will not happen again, like leaving the plug out of a boat at launch, it should only happen once.

Bonzi Lon

[bartsscooterservice]

The battery was installed correctly and things worked right before you removed the battery and put a new one in, so odds are you connected the new one backward. I have seen batteries with the positive and negative terminals reversed. If you didn't match the - sign on the battery with the cable that connects to a starter mounting bolt, and the + sign with the cable that connects to the starter solenoid (where the other wires also connect) then you probably just got your poles switched.

Find the + and the - on the battery top and make sure that they're connected correctly.

Yeah maybe the other battery he installed had the poles reversed and he didn't keep notice of that.

[siteunseen]

Blue swapped his hot post to the outside to keep it from possibly sliding over and arcing on the inside of the fender. I'm sure others have done the same as it's not a bad idea come to think of it.

[Captain_Zeros]

While we're talking about battery posts, if you're not married to originality a GM sidepost battery pretty much eliminates your chances of welding your battery to your fender. Previous owner of my car put one in it and I stuck with it. Just gotta swap the battery cables.

[Darrel]

swap the positive post closer to engine, in stock form the positive post was under the fender.

[Nebulas die]

Thank you guys for the reply. I will take a look into all post because I am curious myself. As for the switched poles, i luckily placed them in the right spot. However, I did remove the rotor head plug that connects the spark plugs. I could have grounded my car? I am still looking for my fusible wires but no shop carries what I want ATM..

I will update if there is fire. I'll try to record it too if it happens!