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My GTO is having problems at night. The alternator (3 years old) is charging the battery - as the battery is not dead and is still relatively new.

During the day, when the motor is at idle (for example, when I slow down to make a turn and depress the clutch for a second or two), the turn indicators will occasionally stop blinking, and will start blinking again when I get the engine revs up a little higher than idle. This has happened multiple times.

In the evening, when I run with headlights on (they are Delta H4 conversions, not T3s), and again when the engine revs drop (such as when at a stop light), the headlight lights will often go dim. And when I turn on the bright lights, they basically disable all headlights (normal and hi beams).

I really need bright lights at night for my aging eyes. And no lights is both scary and illegal. My car does not have much in the way of electronic accessories - really just lights, indicators and spark, and I do not use the radio and do not have an electric fan. Is my alternator under-powered? Should I have the battery checked out?

Questions? Clarifications? Thoughts?
 

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Get yourself a digital multimeter, they aren't that expensive. With the engine idling, in neutral, check the voltage across the battery terminals. If the alternator is in good shape and doing its job, you should see 14 - 14.4 volts.

It also shouldn't drop much, if any, when you introduce additional electrical load such as turning on the headlights.

My suspicion is that your alternator is "going away".

Another possibility is that if you've added additional electrical load to the car such as electric cooling fans, "big" stereo, etc. that the factory alternator just doesn't have enough capacity to keep up.


Bear
 

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What is your idle speed? Should be at least 650 RPM in drive, 850 for manual trans. Alternator will have reduced output at slow engine speeds.

If you still have the original wiring, you probably have a large voltage drop in your headlight circuit, especially with the H4s. Installing a headlight relay setup will greatly improve the brightness of the headlights
 

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Load test the battery, and verify alternator at idle and speed. Take it to any service station/Garage that has a Volt Alternator tester known as a VAT tester.

it will test the e battery by load-testing and the alternator output at idle and 2000 RPM’s in less than two minutes. Then you can go from there. Agree with 052 a headlight relay system will give you bright headlights very easy to do.New wiring harness help as well as old wiring has resistance buildup.

I use MAD electronics wiring system, very very strong but does not look stock.
 
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