pulsing headlights

[68w/sbc406]

my headlights pulsate. i know it is common at low idle but mine do it as i drive down the freeway. i have a new alternator, but is the internal regulator bad? or is it a weak ground or something like that?
Thanks for any info
Ben

[franko72]

check your ground.

[Iminocca]

I had the same problem, It was the voltage regulator. Put a voltmeter across the battery teminals with the engine running and it read 13 - 14.8 volts, pulsing with the headlights. Mines external so it was an easy (and cheap) fix.

[Longhorn Man]

I'll second the checking of grounds...but it is probably a messed up alt/regulator.

[68w/sbc406]

its a 6 month old bosch 78 amp (or something like that) alternator i bought from an electrical shop. so i think that i will make them figure it out

[Iminocca]

The problem showed up on my truck when I went pick it up from my dad. He only drove it occasionally for the last 5 years or so, and almost never at night. There was no ground from the battery to the body, only to the engine. I added one. I had just installed a new alternator (old one had, the original, had a bad bearing) and didn't think that was the problem. If the voltage pulses across the battery terminals, it's probably the regulator. If it pulses only from the positive battery terminal to the body, probably a grounding problem. One of those little digital multimeters that Harbor Freight puts on sale for $2.99 is ideal for this sort of thing. I was getting the truck ready for the 400 mile drive home and needed reliability.

I say all of this because if you take it to a shop that does not offer free diagnostics, they may charge you if the alternator they sold you is not at fault. Hopefully they won't. That, and I just like being able to figure this stuff out for myself when possible.

Also, at 14.8 volts, my battery had been overcharged for an unknown period of time and could have had it's life greatly reduced. Went to Wal Mart and got a new battery too, just in case (400 mile drive home and all).

Patrick

[68w/sbc406]

i am grounded to the motor, but not the frame. i guess that i will throw a strap between the motor and frame and see if that works. thanks for the reply
Ben

[68 Stepside]

Yeah, try the ground strap from the engine to the frame. And from the engine and frame to the body wouldn't be a bad idea either. I had a nasty electrical gremlin when I was driving my 68, if I didn't have the shifter (auto) in exactly the right spot, my headlights would go ape. If I shifted it manually, I'd lose power to the engine, and the headlights would occasionally turn all the way off. I put a large ground strap from the engine to the firewall, and that was that. No more gremlins.

Good luck.

[68w/sbc406]

i should probably get off of my A$$, turn the computer off and go to the store and buy two.

[68w/sbc406]

ok i picked some up. now just waiting for the truck to cool. i was looking for a good spot and the only thing i could find is one of the tranny bellhousing bolts. that should be a fine ground right? and for the cab ground i was thinking about where the inner fender bolts to the cab

[Longhorn Man]

Good places...just make sure you clean the paint and grease off first.

[68w/sbc406]

of course, what kinda hack do you think i am???(j/k) while i was down there i fixed my reverse lights. i have a lokar floor shifter and there is a ball switch that bolts to the tranny that the linkage hits when you are in reverse, i goofed around with that then busted the idiot light out, realized NO POWER. checked the fuse. BINGO didnt have any instock went to the parts store came home put it in found out why i had a blown fuse, light bulb broke hot to ground draws more than a 1156 bulb so i had to go back to the parts store and get a bulb. i went to schucks 3 times today. good thing its close

[61corv]

this may sound crazy but try the footswitch for the high/low head lights. i spent days searching on a 70 camaro for the same thing.

[61corv]

try the hig beam foot switch...i spent days looking for the same on a 70 camaro..

[68w/sbc406]

well last night i didnt notice any pulsing but it comes and goes. have to keep my eye on it. the best part of the whole project was my tach started working again. it hasnt work since i put my V8 in.