I have a 69 cutlass "S" with 350, no major mods just a plain janer. Here's the deal, I drive around fine and everything works fine, but at night while driving all the lights get go up and down slightly ......if I let off and coast they stay one bightness but as soon as I touch the throttle, they start cycling again ....its pretty consistent so I'm thinking alt or reg? the alt has been changed in the past and was a "re-built" but that doesn't mean its good. I have metered out the voltage and its about 14 at the battery.

 

It sounds like you still have the original voltage regulator. They were a mechanical type, similar to your points distributor. When the correct voltage is sensed, the regulator switches off, then when it gets low enough, it "turns" back on. My Rallye 350 has it's original one & does the same thing. I'm sure all these cars did it originally? I think it's kind of neat & as long as you're seeing +/- 14 volts, you're fine. You can buy parts store ones that are all solid state(no moving parts) that won't cycle like that if it annoys you.

 

Yea, the bright then brighter cycling is a real problem, its too noticeable for my liking ....I'm going to go into a seizure if I drive it at night. I'll swap out the reg. 1st then and go from there.

thanks

 

Cheven, before you buy any parts, check all of the electrical connections to be sure they're clean and tight. Especially the battery terminals and cables. Checking connections is free and poor connections can cause all kinds of grief, especially grounds.

 

I checked the voltage again and it was off the scale. Figures, the new replaced regulator went bad so I grabbed a 40 year old OEM delco part out of parts pile and now things seem much better. And I have the factory looking Delco reg. on it now

 

Funny how those 40 y/o parts seem to last forever, compared to ...