Engine dies when headlights are turned on

[bavarian06]

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. Any suggestions?

[Gary in NJ]

Souunds like an problem with the Throttle Opener. What is the condition of the Throttle Opener Servo? There is a vacuum line between the servo and the control line. Is that in place or damaged?

The diagram can be found in the Emission Control section of the FSM.

[bavarian06]

I believe its a short of some type? I banged on the dash n sure enough my headlamps turned on and I was able to start the car. The bundle of wires found nxt to the passenger side upper kick panel had a loose wire, I reconnected and attempt to drive the car. A mere 1mile from my house the car dies again and everything goes dark.

I have a late '70 Z.

Edited January 31, 2011 by bavarian06

[bavarian06]

I think I found out what's wrong.

The wire terminals from two thick gauge wires leading from the fuse box were corroded. Very similar to the wires leading from this fuse box (taken from another forum member), you see how the white colored wire's terminal are blackened from corrosion and burns.

Maybe it's time to invest in a new fuse box.

[bavarian06]

What I couldn't figure out was why was I able to start the car, turn on the parking lights, but once I flicked the headlights on, the engine would die.

Is this a voltage issue? Obviously some kind of current was being sent through, just when the headlights were on, it overloaded it? I have the parking light hardness upgraded installed already.

[SteveJ]

Art,

Do you know how to use a multimeter? If so take voltage readings at your battery

1. when the car is off

2. after the car has been started

3. at 2000 RPMs

Also check your alternator and belt. Is the alternator turning? Does the belt have enough tension?

In the early Zs like yours, the headlight switch completes the ground path for the circuit, so it isn't a short. Search around this site. Dave, aka Zs-ondabrain, posted a link for the 71 FSM supplement. That has the wiring diagrams in it.

By the way, it is helpful for you to put the year of your car in your posts.

Good luck and let us know what you find out.

[Walter Moore]

In the early Zs like yours, the headlight switch completes the ground path for the circuit, so it isn't a short. .

Ah, but if some part of the circuit that the ignition depends upon is partially shorted to the wiring for the low beams or high beams,(either a Red/Black, or Red/White wire. The schematic isn't clear to me.) then "turning on" the headlights would pull the voltage to the ignition circuit to ground, and the car would stop running.

[Walter Moore]

By the way, I have had problems with the fuse clips getting loose and having too much voltage drop in between the fuse and the clip. This can cause all sorts of strange and difficult to diagnose electrical gremlins. It is also the reason that you see so many early Z's with melted fuse boxes.

Motorsports Auto, among others I suspect, sells a replacement fuse box. Personally, I just used small Ty-wraps around the base of the fuse clips to increase the clamping force on the fuse. It is a good temporary fix, but it does mean you need needle-nose pliers to remove and insert fuses.

(Disconnect the battery before trying to install the wire-ties, or sparks may fly.)

[SteveJ]

Ah, but if some part of the circuit that the ignition depends upon is partially shorted to the wiring for the low beams or high beams,(either a Red/Black, or Red/White wire. The schematic isn't clear to me.) then "turning on" the headlights would pull the voltage to the ignition circuit to ground, and the car would stop running.

In a stock configuration, the wires for the headlight circuit are not on the same connectors as the ignition. The only ways they could short is if the wiring was hacked or if the insulation had melted in the harness.

Since the OP has barely done any diagnostics for us to give a reasonable suggestion, it's best to wait for good information before speculating.

[SteveJ]

Art,

One other thing to look at is where is the needle on the ammeter. If it's pointing toward the negative side with the car running, it means current is flowing from your battery (discharging). If it is pointing toward the positive side, it means the alternator is charging the battery.

[bavarian06]

thanks everyone for all your help. i havent had the chance to diagnose the problem since this weekend has been pretty hectic.

i did however pull the headlight and turn signal stalk and the fuse box. from first glance, nothing seems to be wrong with the headlight and turn signal stalk. all the wires are still soldered on, the tiny brown circuit chips dont seem to be blown/damaged.

as for the fuse box, the actual clamps that hold the fuses in place are solid. the plastic fuse box housing isnt melted. the only bad part is the terminals leading from the long pig-tails. the pictures shows the points blackened from heat and there is corrosion.

basically i'm going to install new male/female connectors, dielectric grease the points and hope for the best.

near the passenger kick-plate area, coming down from the dash, can anyone tell me what this part is? i hear this component clicking when i rock the ignition switch from ON to ACC. is it possible this may be the culprit?

you can see my mickey mouse quick fix (the yellow and blue connectors). basically the original connectors literally snapped off from being so brittle from all the heat. this strand of wires leads from the fire wall and up into the dash (where i assume goes to the fuse box, headlight switch, etc). i think something else might be loose or have a bad contact there as well.

[bavarian06]

Art,

One other thing to look at is where is the needle on the ammeter. If it's pointing toward the negative side with the car running, it means current is flowing from your battery (discharging). If it is pointing toward the positive side, it means the alternator is charging the battery.

the anmeter is pegged dead center, has been like that since i owned the car.