KY72LT1

With engine running I pulled the Head light Switch and the engine shut down off just like I had turn the key off. After further checking and trying every combination of lights on/off, jigling ETC.., it just wasn't the engine, the electrical system had shut down past the selinoid connection ( got 12V on the Pos Batery cable at the starter). The interior lights would not even come on. To make it even worse I had it towed to my house the next day still no power, put it in the garage set the park brake, forgot to turn the key off but no buzzer or Alt lights were on, still dead. I come out the next day and the park brake light is on, the interior lights work and IT STARTS? I pullled the Head light switch real slow and the lights dimmed but it still ran, then I pushed the switch back in and pulled out Fast/ Normal and it shut down just like before. I know this is not a vacuum problem. Does anybody have a clue ? I don't just want to start replaceing parts, PLEASE HELP!
Thanks in advanced, Ben

Sully1882

ok... i am by far no expert but yes this is no vac problem! It is potentially very dangerous too. If everything is shutting down when you pull that headlight switch there might be something wrong with the switch, old or worn out! the power for the headlights and such go through that switch and if when activated it is shutting down the whole car then there is a short that is overloading the main electrical system. Dont play with this and dont drive the car again until you get this fixed, you definately dont want to cause an electrical fire and lose your whole car..... someone here will have a better in depth answer for you! But you should also think about going to docrebuild.com and getting a good wiring diagram, this way you can trace through the electrical better.... hopefully the switch is just bad


good luck!!!

Sully

...Roger...

Its obvious from your post that you have decent knowledge of a cars electrical system.
So your saying you had 12v at the pos batt cable at the solenoid but when you checked the wire on the same post as the batt cable going up to the harness you had nothing?

bj1k

The first thing I would do is a battery check. It could be a shorted cell. Then I would suspect the switch if the battery checks out.

ripforrey

It is $ well spent to purchase a wiring diag. I have one of the 3'X3' laminates.
Start with the easy and cheap stuff and eliminate that.
There are lots of others with more experience than me, but, I would start by checking the charging system, are you getting app. 14v with car running? You could have something as simple as a loose alt. belt. Then go from there.
Your problem may not be with headlights. With car off and charged batt, do the headlights work? dim? not at all? You just see the problem with hl on because of the additonal current.
You could have a poor ground, or connection or loose or frayed wire; easy to say, PITA to find. I saw a post where the hood release cable frayed wires.
Good luck

KY72LT1

I just disconnected the battery. It is new and still good. I will start a complete wiring harness inspection after the holidays. Has anyone changed the front engine and light harnesses? How long does it take?
I am thinking that it maybe a good idea to replace them since they are the originals? Any thoughts replacement vs original?
Thanks again,
Ben

Sully1882

good idea on replacement...........lectric limited brand is perfect. This was my first project on my 72 and it went nice and easy... did the engine harness and the front lighting in just a few hrs. Label everything there with tape as soon as you disconnect.... keep the old harness for reference...and get those wiring diagrams from Doc Rebuild...

best of luck,

Sully

greg454

Sounds like a bad battery or a bad connection somewhere. Put a meter on the battery terminals with the car running and you should see something around 13-14 volts. Leave the meter on the battery and turn on your headlights--If the battery voltage drops way below 12 volts you have a bad battery (probably drop way down). If the voltage at the battery stays up around 12 volts (it will drop down to about 12 volts when the car dies and the alternator stops charging) and everything electrical stops working then you probably have a loose or bad connection on the battery itself, the starter terminal, the horn relay juction block where most things are powered from or you have a bad ground connection to the frame or engine. You say you had 12 volts at the starter, but that would be normal for a loose or bad connection when there is no electrical load so that doesnt really help unless you measured it during the failure mode.

Hope that wasnt too confusing.

Greg.

Vetteaddiction

All these suggestions are good but...
Do you by any chance have an aftermarket ignition system?
I had the Pertronix ignitor LS which someone had installed but wired incorrectly. The module needed 12v at all times and wasn't getting it because it was wired like normal points through the resistance wire. When I turned on my headlights while engine was at idle the motor would stall - not enough volts to even power the module.

Just another possibility, good luck
Chris

0Willcox Corvette

Ben,

I'll be in on Monday. . . Give me a call or run over to the store, well talk about this.

Willcox