Engine dies when headlights are turned on

[SteveJ]

ok, i'll definitely will test the voltage once i get the chance.

can you possibly answer this qt?

"can someone explain to me why would the parking lights work (along with the dash lights, dome lights) but once the i rotate the stalk once more to turn on the headlights everything goes dead/dark."

it was almost comical when i banged on the dash and the headlights turn on; hence being able to start the engine. as mentioned in previous post, i think its the male/female terminal connectors needs to be replace leading out of the fuse box. cause when i banged on the dash, it probably shook that strand of wires, getting a better connection?

The issue could be with your fusebox or the back of it. Corrosion can play a lot of tricks with the electrical system. You've already seen the effects of 40 years of aging on wires.

Keep in mind that the headlights are on a completely different circuit from the parking lights. For the early Z cars like yours, the positive side of the headlight circuit does not even go through the combo switch. If there is a loose component (wire, fusebox, etc.), banging on the dash could move the component to make or break a fault.

The back of the fusebox is NOT insulated, so there is the danger of a loose wire or fusebox wreaking havoc.

[bavarian06]

Next baffling thing is:

being able to turn on headlights = being able to start the engine. Why?

The car died numerous times while I was tinkering around with it last Friday. Everytime I was able to get my headlights to turn on, I knew I was able to start the car.

[Zed Head]

Next baffling thing is:

being able to turn on headlights = being able to start the engine. Why?

The car died numerous times while I was tinkering around with it last Friday. Everytime I was able to get my headlights to turn on, I knew I was able to start the car.

Your first post said "My car will start but the engine will die out once i turn on the headlamps. The car will run with the parking lights on but once I switch it one more level to turn on headlights, it turns off. "

What you're saying at the top here is different. Has something changed or is one these statements not right? First the car would start then die if you turned the headlight switch to on. Now the car won't start unless the headlights are on? Almost opposite statements, so hard to figure out what's going on.

Either way, one good way to problem solve is to isolate circuits. Unplug your headlight switch entirely and see if the car starts. See if it starts with the headlights on low beam and high beam. Take some fuses out and see if one fused circuit or another has an effect. Eventually you'll narrow it down to one area.

[bavarian06]

good observation. you are correct, initially the engine will cut out once i flicked on the headlights. after doing a quick splice and connect with what i had (reconnected the wire near firewall), the engine would only turn on when i was able to turn the headlights on.

[SteveJ]

Next baffling thing is:

being able to turn on headlights = being able to start the engine. Why?

The car died numerous times while I was tinkering around with it last Friday. Everytime I was able to get my headlights to turn on, I knew I was able to start the car.

This makes much more sense than the original problem description.

The answer would be that you have a dead short somewhere between the fusebox and the battery. The real question is why didn't the fusible link burn out?

Anyway, the ignition and headlights branch off the same circuit between the battery and fusbox. Therefore electrically they are the same wire. If that wire is shorted to ground, such as can be the case with a loose fusebox, the ignition and headlights would not operate properly, since the current from the battery is going to ground.

If you break that contact to ground, the headlights would work, and so would your ignition.

[SteveJ]

good observation. you are correct, initially the engine will cut out once i flicked on the headlights. after doing a quick splice and connect with what i had (reconnected the wire near firewall), the engine would only turn on when i was able to turn the headlights on.

Hmm, this adds a twist and gets my wheels turning. I think I have a better idea of what's going on. I'll have to copy some information from the wiring diagram (at home) to explain it better.

[bavarian06]

Hmm, this adds a twist and gets my wheels turning. I think I have a better idea of what's going on. I'll have to copy some information from the wiring diagram (at home) to explain it better.

i appreciate the help steve.

but you dont have to trouble yourself to great lengths, though i appreciate it. issues like these puzzles me and i always like to find out why (i'm very curious in nature).

this is exactly what happened last friday night: i had parked the car at 2pm and didnt drive it again until 6pm (dinner plans). i guess the car had cooled down too much and was struggling to fire up. instead of using the choke cable to feed her more gas, i blipped the throttle instead. what happened after that seemed be the sound of the car back-firing and the engine cuts off.

i restart the car and but notice a more apparent noise from the accessory relay in the process of cranking the ignition switch. the car re-starts, i turn on the headlight switch to first level, engine stays on, switch it to second level (headlights on), engine cut outs. i repeat the process over again and sure enough, everytime i switch the headlight stalk to second level, engine cuts out. i was tempted to drive without the headlights but i figure i better not risk it (friends were calling me from the restaurant telling me to hurry at this point).

i started to poke around the wires. since the accessory relay was making a lot of noise, that's where i first started. i found the female spade connector on the verge of snapping off on one of the thick gauged white colored wires. without much force, the spade connector snapped off from the wire while i was checking for its integrity. i tried to mend the connection with what i had in my garage at the time (hence the mickey mouse job). i was so confident that would fix it but the engine still wouldnt stay on with the headlights on.

i canceled my dinner plans and ended up tinkering with the fuse box (none of the fuses were blown or distorted) wires cause i was trying to see where the bundle of wires from the firewall were leading to. after the tinkering, the engine wouldnt start period. out of frustration, i banged on the dash, and sure enough the headlights came on and i was able to start the car. :stupid:

[SteveJ]

Hopefully this helps.

This is taken from a wiring diagram contained in the 71 FSM Supplement that Dave, aka Zs-ondabrain, posted a while back.

Positive for the ignition switch and for the headlights comes from the White/Red wire. The White wire comes from the battery, goes through the alternator and supplies the White/Red wire until the alternator can.

First scenario - You start the car, turn on the lights and the car dies. The alternator/battery cannot supply enough current. (Shorted alternator or bad voltage regulator maybe?) Without enough current, the car dies.

Second scenario - You move wires and replace connectors. Maybe you bypassed the alternator and are pulling from the battery only. Your headlights work and the car will run...until you drain the battery.

Again, the voltmeter will give better information.

[Zs-ondabrain]

OK, lots to read and my gears are smoking. Sounds like Steve is on the right path.

I would personally start with repairing those connections at the fusebox. putting the ACCesory relay back where ya found it (screw it back to the kick panel on the passenger side.)

So it sounds like there is just enough voltage transfer to power either the headlights, or the ignition. bad connections, corrosion, burnt copper, etc could be the issue at hand.

Some Fusible links can actually look good and be bad on the inside of the sheath. Give it a tug and make sure all is good. Also use a test light to see if both ends are conducting electricity.

Voltmeter, put the dial to DC on the 20 volt mark. This will test voltage safely up to 20 volts DC. Connect the black wire to a good known ground. Thest use the red wire to test to your little hearts content.

Start with the battery. Test the battery and write down the voltage. (12.5 volts? maybe

Start the car and test the battery again, write down the results. 13.5 idle to 14.5 at 1500 to 2000 RPMs. basically, you should see 1.5 to 2 volt increase with the engine running. if so, alternator may actually be good.

What are the chance that the wires on the Ammeter in the dash are loose or bad?? Check EVERY connection dealing with the White and White/red power wires. Alternator, battery, starter and fusible link, under the passenger side of the dash, at the fusebox and the ignition switch. every one of those area's has a possiblility of being your trouble spot.

GROUNDS, GROUNDS GROUNDS....... I can't stress this enough when helping people troubleshoot electrical issues in their cars, Every car, make and model.

Pull the battery terminals, clean the posts and the clamps, follow the ground wires to the firewall and Clean it. reground it (grind metal if you have to)

Below the battery, above the frame, is a groundwire, bolted to the body. Pull it, clean it, clean the connector and metal, re bolt it down. Then spray a little matching paint over it to keep the connection and metal clean of moisture and air.

These things should keep ya busy and might even resolve the issue. So do those and get back with us...

Dave

What are

[bavarian06]

front of fuse box:

rear of fuse box:

spade terminal:

turn signal:

headlight switch:

[bavarian06]

the two white wires are pretty burnt and corroded. is it ok to just cut off an inch off the ends and re-clamp new female connectors to it?

i really want to work on the car now but i have an upcoming race this sunday i have to prepare for and then the following weekend i have surgery. i'll keep everyone posted on the voltage meter readings.

Edited February 1, 2011 by bavarian06

[Zs-ondabrain]

Those are some classic switches. they don't look too bad either.

If you feel you really need to cut then connectors off the white power wires, cut them as close to the connector as possible. otherwise it'll be shorter and likely more difficult to make the connections when reinstalling the fusebox.

I'm in the process of looking for that type of 9.5mm? connector and the silicone boots that come with them. I hope to find them soon, so you have a viable replacement.

Dave