Running Poorly With Headlights On

Now that we are starting to bring our cars out for spring, the tech questions will finally start to proliferate.

Here's my question. My car seems to run substantially rougher (consistent missing) at all RPMs when I have my headlights on. I have H4s with bright bulbs. I still need to install a relay. I have one batttery instead of two. Everything else electrical is stock.

I have also noticed that my dash lights will be normal (pretty bright) for 30 seconds and then the dash lights (and headlights) noticeably dim for a while -- to the point that it is hard to read the gauges. This happens without any change in RPM. Is my alternator on the fritz or what?

Any ideas?

Might try charging the battery overnight. Your alternator will love you for it.

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Robert Stoll
83 SC
83 944

As a precaution, I'd keep a fire extinguisher in your car until you've got this figured out.

you may not have enough charge from the alternator due to it being unable to put out sufficient amperage, or the regulator unable to control the voltage evenly at 13.8 to 14.2V when you put a load on it. you need to check voltage and amp. output on a charging system checker, on which you can crank in a 150A load for 15 seconds max. while you raise the RPM to 2500. a 69 should have a 50A alt stock, so you should get up close to that when it's loaded.