Reversed Battery Cables

[priest]

I own a Datsun Roadster 1600 - Year 1970 - L20B motor

 

So I did something incredibly stupid today. I placed the Positive on the Battery Negative Terminal, and vice versa just for a second or two. Realizing my mistake, I immediately removed the leads, and waited. There was some hissing near the headlight relay, some slight din of smoke, and the all to familiar smell of burning wire insulation. 

 

Question: I figured the battery is reversed and finished off. That is the least of my problems. What else could I lose:

 

Power Regulator

Relays

Capacitor

 

Any information is helpful

 

Thanks,

 

Priest

[datsunaholic]

Coil and capacitors, probably not.  Depends on if you turned on the key, but the coil can handle being backwards.  Without the key on, voltage regulator and alternator.   Alternatpr would be the first thing to self-power, because the diode trio would provide no protection with reversed connections (in fact the alternator would try to become an electric motor, which might have fried the alternator's output wire.    Maybe headlight relay, but that's unlikely.  With key on, lots of relays might, along with anything electronic- radio, EI ignition, that sort of thing.  actually an aftermarket radio could go even without the key, since the clock/memory wire is always hot.

 

But I'd start with the wire between the alternator and battery.  And the voltage regulator wiring.

[flatcat19]

You could lose a lot more than just those listed.

 

Hook up your battery, properly, and watch the smoke show.

 

I'm sure it is nothing more than a quick rewire of smoked circuits.

 

 

 

And pics of your L20B'd Roadster...

Please!

[Skib]

you can cook just about anything.

[ggzilla]

The battery itself is unlikely to be "finished off".

[thisismatt]

Relays shouldn't be affected either. They just won't engage if their coils see a reverse voltage. Alt would be my first look.

[DanielC]

The battery is probably fine.  It normally more current starting the car, than you need to fry the diodes in the alternator.  the alternator is probably not OK.  Check any fuse links, you may have.

 

The lights do not care about polarity.  The coil does not either.  If you have points, they are probably OK.  A matchbox distributor, on the other hand may not be.

[datzenmike]

No worries you can still get the Lucas replacement smoke kit.

 

and get that smoke back in the wires.

[DanielC]

That is just normal replacement smoke.

 

It is going to be hard to put the magic smoke back in semiconductors, like the alternator diodes, and other electronic parts.

[gearboxx70]

When I had my 510 back in the late 80's or early 90's, I nearly welded a ratchet to my engine block. I was changing spark plugs and dropped the ratchet on top of the hot lead to the starter and it wedged against the block. After the sparks and smoke had cleared, I'd toasted my condenser, alternator, voltage regulator, starter solenoid, and ignition switch. That was an expensive "clumbsy me" moment!

[uieluck]

I did this EXACT thing after I'd been drinking 'soda',, search my posts there's some good answers and suggestions. It was on my goon', I got lucky, no major fry-age.

[priest]

First off, love the smoke replacement kit.

 

As for the car - the ignition was never engaged (thank goodness) when I encountered the smoke generation with the battery reverse connected.

 

Here is where I am at with the battery connected the correct way:

 

Battery checked OK.

 

There is zero power to the car, headlights, etc. with or without the ignition engaged with the battery cable in the correct place. 

 

Acrid smell of burning under the dash (leads me to the Power Regulator possibly). Could have fried the alternator, but since it is 15 year old, might be time to replace it.

 

Any guesses. Fortunately, no smoke with the cables correctly hooked up, since I have no power.

 

I'll see if I can get a few pics out there Flatcat19

[datzenmike]

Check your fusible links, that's what they are for.

[priest]

That makes the most sense. Sounds like a wire trace. I plan on taking the dash off anyways since it need to be recovered, so that would be a good time to "get into it" and figure it out. In any case, the alternator and Power Regulator are getting replaced. 

 

BTW, were fusible links stock to the 1970 1600s and 2000s? I did hear that the earlier Roadsters had issues with parts of the engine or dash bundles burning up. 

 

Thanks for the great advice guys!

[flatcat19]

Continuity will be your friend.

Buy a decent DVOM.

[ggzilla]

What's a "Power Regulator"? Do you mean the alternator voltage regulator or the instrument panel regulator?

[priest]

Yes, Voltage Regulator. 

 

 

[priest]

You called it KingRat. Found the fusible link attaching the starter motor to the dashboard connection. Melted straight through. 

 

It apparently has a part number 24018, A339 0, G69 T2...

 

Appears the hot (thickest wire) is what burned through, which makes sense. I am assuming this connection is finished.

 

So the question is, should the connection be tossed, or somehow reused? Spare connections?

[its_karl]

they sell fuseable link, just splice in a new one

[datzenmike]

Just get the same diameter wire for the same protection. Hopefully it saved everything past it that goes to the fuse box.

[brodster]

Priest,

 

Like mentioned above, definitely just replace that fusible link. Typically they are just a fuse where it is impractical to install normal fuses. Here's a link : http://www.madelectrical.com/catalog/fusible-link.shtml

 

I don't mean to be super negative, but I am a bit concerned that other stuff may have been damaged or severely strained. Luckily on these old cars, most components like relays can be hooked up backwards just fine. Your battery is okay too.

 

But those fusible links don't blow instantly, which means there was a butt-load of current flowing somewhere. In other words, the fusible link is the symptom but not necessary the fault.

 

Unfortunately I can't view any of the wiring diagrams because the links have been down for awhile, so I can't help you trace down the exact culprit. Regardless, fix the fusible link, and do a brief check for anymore overheated elements. Check associated fuses. Go under the dash and start sniffing around, literally.

 

You mentioned there is an L20b in the car. Is there any added circuitry off that affected power line that may not be fused?

 

If we can't find anything, probably just hook the battery back up (correctly  ;) ) and see what doesn't work.

 

There could have been just some strain or moderate damage on some electronics which may just be something will fail sooner than later. Maybe nothing will result.

 

Good luck and don't kick yourself too hard. Many of us, including myself, have done way more stupid things. For instance, I was working in a lab once and trying to trim the power leads on a LiPo battery. Being in a rush and trying to save time, and obviously not thinking, I decided to trim both leads at the same time with a pair of diagonal cutters: Short circuit! LOTs of smoke and potentially very dangerous considering it was a nasty LiPo battery.

[EricJB]

No worries you can still get the Lucas replacement smoke kit.

 

and get that smoke back in the wires.

 

 

 

 

Why do the British drink their beer warm?

 

 

 

They have Lucas referigerators.

[exit64]

The other fusible link is the ammeter in these cars.  On the 70 it is shared with a couple of other gauges, stand alone on the low windshield cars.  All the wiring diagrams are over on 311s.org in the tech wiki.  They are easy to print our real big and then lay it over the windshield, print side in so that you can just sit in the car and mess with the wiring.