Electrical issue: headlights as a kill switch?

[Derek An]

I have an issue with my 1960 356
Recently I have been having a problem
Where if I turn on my headlights the car power shuts off and when I try to turn on the car again there is no power to anything but the horn?no dash lights no ignition etc.

Last night I was driving it and needed headlights... It had worked earlier and I didn't see a problem.
I was cruising at about 50mph when I turned on my headlights and it was like I hit a kill switch for the car. Everything shut off and a slowly rolled to the side of the road.

Now the car is completely dead and I haven't gotten it to be able to start up after 20-30 mins like it did before.
I don't get any power to anything in the car except the horn.

None of the fuses under the dash are bad and I have wiggled and moved just about everything I could.
The battery still has power. I've checked all the contacts and connections several times

Located in LA

Any recommendations for a good person for electrical in the area or does anyone have anything I can try?

[David Jones]

On the back of the light switch connection #30 comes from the fuse block connection #2. Connections 1 2 and 3 are ganged together on the fuse block so if you have power there then there should be power at the light switch. Connection #30 also goes from the light switch to the ignition switch and this is where your problem may be. Check that connection and see if it is loose or missing.

[Geoff Fleming]

Derek,
When you say you haven't been able to get it started, "after 20-30 minutes like it did before", are you saying that is the normal amount of time it took? If so, you have had a problem for some time!
The engine should start after a few seconds, as long as you have fuel in the carbs and decent timing. I do know some newer owners, not being used to carbureted cars, try and start by simply turning the ignition key and not using the gas pedal. That may work for fuel injection but not older cars.

[Derek An]

Derek,
When you say you haven't been able to get it started, "after 20-30 minutes like it did before", are you saying that is the normal amount of time it took? If so, you have had a problem for some time!
The engine should start after a few seconds, as long as you have fuel in the carbs and decent timing. I do know some newer owners, not being used to carbureted cars, try and start by simply turning the ignition key and not using the gas pedal. That may work for fuel injection but not older cars.

The electrical power would go out for about that much time. Very strange. Has nothing to do with the carbs or fuel. Imagine a kill switch on a motorcycle. Everything just dead.no power to anything. I would just wait and fiddle with wires and switches for a bit and then it would just come back. Turn the key and lights and everything would function as normal.

[Jim Alton]

I'm supposed to be an electrical engineer and this sounds strange to me. It's hard to see how a simple electrical system like a 356B could be time sensitive like this.

One thought: could there be a short in your headlight wiring that creates an extreme load? That could be checked at the headlight switch with an ohmmeter. I would recommend checking for shorts before doing much else; short circuits can be dangerous.

It might be interesting to watch the system voltage before and after the headlights go on (and the car dies).

It might also be interesting to see if the car can run with the headlights on if a battery charger's connected to supply extra power (after we're fairly sure it's safe).

If there's an old-school automobile electrical shop left on Earth that can work this it's probably in LA, but I don't know where it is. I asked a friend who might know of one.

[Pat Daily]

Double check the fuse block and make sure connections are good. I had a problem some years ago that was similar--everything went dead and I checked the fuse block and it was warm. Jiggled the wires a bit and got it started and drove home. Replaced the fuse block as it was partially melted.

[Jim Alton]

It occurred to me that a test to try (at least if it were my car) is to open up the headlight buckets and pull the electrical connectors from the headlight bulbs.

If all the wiring's in order, there should be an open circuit whether the headlights are switched on or not. If the car dies when the [disconnected] headlights are switched on, there's most likely a wiring problem or switch malfunction.

Otherwise, it's really strange. Maybe some strange voltage regulator function.

Well, that's a diagnostic step I might take, but if the information to be gained doesn't seem useful to you, don't run the test just to amuse me.

[Ivan Fuller]

As David mentions there is a bridge on the back of the fuse block - this is riveted in place. It connects the battery supply voltage to headlights/ignition. Its not uncommon for this riveted connection to become loose or dirty, the extra amperage when turning on the headlights will cause the poor connection to heat up increasing the resistance in the circuit. When the load is off and things cool down a continuity check for voltage will appear normal - I would not be surprised if checking voltage at the coil with lights and ignition on that you have way less than 6v. Usually you will be able to see scorching of the bakalite/plastic in the area around the rivets on the back of the fuseblock - it will be the bridge across three terminals not two. It can be repaired by cleaning and soldering around the rivet or replace the fuseblock. Tightening the screws and checking wires for tightness will not address this issue however as mentioned this needs to be done on the small red wire wires at battery terminal, fuseblock -2,3,4, headlight & ignition switch #30. Odds are if its not the back of the fuseblock it will be the small wire dirty at the battery clamp - make sure there is not corrosion up the wire - an acid spill could wick up the wire and cause a fault there. The connections will be hot to touch in the "failed" load condition. If replacing the fuseblock make sure you get a 356 not a 911 one - they look the same but the bridges on the back are different.

[Leo Hudson]

Had same problem with a 59 coupe years ago. Returning from a from a 356 Holiday in Steamboat it was getting late and as we were pulling off main road to stop at a motel for night I turned on lights and car died. Turning off lights car would run. In the morning I ran a jumper wire direct from fuse block to #30 on inignition switch and car ran fine. As David said power to ignition switch goes through the headlight switch. Solved problem by changing out headlight switch.
Leo

[tony apcar]

Believe it or not...turn on the lights ..the car died ..it was the headlight bulb making a short.. i still have the bulb.. marked..do not use...

[Derek An]

Hi guys,
Thanks for all your great help.
Finally got around to dive under the dash.
Pulled the fuse box and its warped and cracked from the heat on #4
I'm going to get a new fuse box.
Hopefully that was the only issue!
Will let you guys know the results.