Headlights & brake applied engine dies - Team Camaro Tech
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post #1 of 8 (permalink) Old Jan 15th, 06, 02:27 PM Thread Starter
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Unhappy Headlights & brake applied engine dies

Need some advice. When my headlights have been on for a few minutes the voltage slowly drops from 13.8 down toward 12.5 but when the brake pedal is applied the voltage go's below 12 and the engine dies. I had already replaced the battery and the car runs fine when the headlights are not on. The voltage at the battery is 14 at the alternator is 14 at the horn relay 14. the alternator is a internal regulator. Voltage meter is hooked up at fuse panel. all voltages were checked with a separate voltmeter. Don't know where to start to look for a short. Help


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68 rs 350
M-20 4-speed
10 bolt 8.5 3.23

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post #2 of 8 (permalink) Old Jan 15th, 06, 03:52 PM
 
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Re: Headlights & brake applied engine dies

How strong is your Alt? I had a problem like that too, cept, my stereo kicked the battery dead. Turns out, my alt wasn't strong enough. I had an 80 Amp Alt, but I stole.....borrowed..... My bro's 100 Amp. ( I think Amp, not an electricity person.) Gotta love those Iroc's they have some nice stuff I can take.
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post #3 of 8 (permalink) Old Jan 15th, 06, 04:31 PM
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Re: Headlights & brake applied engine dies

Are you saying that the voltage at the battery and alternator is 14 volts, but at other places it falls to 12 volts and below? If that is the case, somewhere you have a bad connection eating up 2 volts. If this sounds right, read on.

The bad connection can either be in a power or ground circuit somewhere. Power circuit connections like the fuse panel, firewall bulkhead connector, or ignition switch. There may also be a bad connection in the ground circuit - like the fender connection to the negative battery cable.

Figure out a way to extend the leads on a digital volt meter. I like to use a ong wire with alligator leads on them. In a pinch, a jumper cable will work - it's way too big, but handy and makes a good connection to the battery. Extend the negative lead of the meter and connect the other end to the positive post of the battery (be careful to not let it touch ground). You can then begin measuring the voltage at several different power points of the system. Good starting points would be IGN fuse (both sides), ignition switch, ignition feed to the distributor, and horn relay. You wouldn't need the engine to be on for this, but you would need the IGN to be live. Take your readings with and without the lights on since they are affecting your problem. Your reading should be very near 0 volts, though you may see a couple 10ths of a volt depending on the place in the circuit you test. From what you describe, it sounds like 2 volts or more is getting lost somewhere.

If the hot side doesn't reveal a problem, check the ground. Just move the jumper cable to the negative post of the battery. You can leave the meter hooked up as is, though you'll read negative voltage, or you can reverse the meter leads. Now check all the ground points in the system, like the fender, dash panel, engine block, etc. Again, you should see near 0 volts.

If during either test you see a large voltage drop (like 0.5 or more I'd say), there is a bad connection somewhere in the circuit between your meter leads. A schematic is a good tool to help you navigate your way through the various circuits.

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post #4 of 8 (permalink) Old Jan 15th, 06, 05:33 PM Thread Starter
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Re: Headlights & brake applied engine dies

Thanks for the replys, the alternator is a 62 amp model. The car runs fine and maintains a 13.85 on the car volt meter as long as the headlights are not turned on. When they are turned on within 5 mins the voltage begins to fall. I checked the voltage without the lights on and all reading looks good. When the lights are turned on, I checked the battery with a digital volt meter and it reads 14 volts and at the alternator reads 14 volts however inside the car I see the voltage meter slowly start dropping to about 12.5 volts and when I step on the brakes the engine the inside volt meter dips below 12 and the engine dies. now if the lights are not on and you step on the brake I see a voltage drop in side the car of about 1/2 volt which I have been told is normal if the volt meter is hooked up to the inside fuse panel. Is that true? the car is a 68 RS if that means anything.


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68 rs 350
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10 bolt 8.5 3.23

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post #5 of 8 (permalink) Old Jan 15th, 06, 05:39 PM
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Re: Headlights & brake applied engine dies

The only time my inside voltmeter fluctuates like that if is the turn signals are on, you can see the needle pulse iwth the flasher, about half a volt.

I'm thinking you could have 1 of 2 things happening.

Thing 1 would be a bad connction, as Dave suggested. I'd guess either at the bulkhead connector on the firewall or the black fusible link coming off the horn relay.

The other possibility (remote from your test results) is a problem with the voltage sensing wire to the regulator. This is the red fusible link into the regulator.





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post #6 of 8 (permalink) Old Jan 15th, 06, 05:57 PM Thread Starter
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Re: Headlights & brake applied engine dies

I failed to list the blinker on as a also causing the inside voltmeter to pulse as Jim has stated. I now have a place to start looking tomorrow and will check the grounds and do some testing as Dave has stated Thanks guys I will let you know what I find.


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68 rs 350
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post #7 of 8 (permalink) Old Jan 18th, 06, 05:17 PM Thread Starter
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Re: Headlights & brake applied engine dies

Just started checking car today. Previous owner did wiring when converting to an internal regulator alternator. On the alternator the F nand R connector. The R is connected to a brown wire that I think must have been to the old voltage regulator and the F is connected to the junction connection going back to the battery. Both the blue and white wires are cut and taped off is this correct?


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68 rs 350
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10 bolt 8.5 3.23

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post #8 of 8 (permalink) Old Jan 26th, 06, 12:40 PM Thread Starter
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Re: Headlights & brake applied engine dies

As some added help I purchased Larry Dubois 1969 camaro wiring diagram I would recommend it highly. I went through my wiring and wired it as the diagram shows where approprate and cleaned up the grounds and replaced some wires that had numerious splices. The cars with the lights on no longer dies when the brakes are applied the lights are brighter and I'm alot happier. thanks to all that replied for help.


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68 rs 350
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10 bolt 8.5 3.23

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