JackBronson

Backing up in the driveway and all of a sudden the car just died. No warning, engine died and the power cut (headlights were on). nothing happened immediately before it happened. It was like an EMP went off next to the car. There was no electrical, as if the battery was disconnected.
Its a newer battery (2 months old) and has 12 volts. The ground at the block was fine, was getting 12 volts from the battery when grounding the test lead from my meter on the block.
Then, after a couple of minutes of messing around trying to figure out what happened with a meter, checking for 12 volts at different points, everything was fine again. good electrical and it started right up.

so, the question is: what exactly would have to be disconnected in order for the car to just outright die with no power? what sort of thing would cause a sudden and total loss of electric?

Thanks.

Vintage Chief

IGN SW comes to mind.

Also, you might indicate the year and model vehicle - this generally assists anyone providing assistance.

72455

When it died, did you still have lights?

joe_padavano

If this happened when the car was running (so there was alternator output as well as battery), I'd look to the common points in the wiring diagram. The power stud on the horn relay comes to mind. I've had problems where that came loose or got corroded, causing symptoms like this. Also, don't be surprised to find that you have corrosion inside a crimped terminal connection.

JackBronson

No. When it died, the engine stopped and the lights including the gauge lights went out. It was like someone pulled the plug and everything stopped/went dark. and there was no precursor symptoms, just went kaput.

JackBronson

Yes, year and model. that was dumb of me.

72 Cutlass Supreme.

joe_padavano

On a 72, the only place that all those systems are common is from the stud on the horn relay to the fusible link and red wire that runs to the firewall connector, and then from the firewall connector to the buss bar in the fuse box. Start with those. And while the fusible link cannot blow and then heal itself, it CAN have a bad connection between the fusible part and the regular wire part. This is unfortunately inside the molded splice cover and not able to be checked without destroying the cover.

JackBronson

OK, so that is the Horn Relay Junction Block as called out in the wiring diag? I'll check that.

My first thought WAS a fusible link when it happened. And after a few minutes messing around under the hood I opened the door to check voltage at the fuse block, and the interior lights came on.

I've been driving it around town today doing errands, and no issues. Of course I'm a little rattled hoping it doesn't cut out at a light or getting onto Route 1...

72442455

On my 72 - When I replaced the battery, positive & neg cables and starter, I unwittingly shortened the wire from the starter solenoid to the horn relay - it was routed firmly back and up against the lower edge of the engine block - a few short runs it did fine - But with the heat and vibration it didn’t take long to melt that wire - as it started to go I had intermittent power (all or nothing) once the wire went it was nothing at all. Just sharing as this wire can cause your symptoms - not necessarily from my numb skull method - but loose or corroded contacts could be culprit