Headlights dim

[1967RSxxx]

Just bought a 67 rs and the headlights sim dim to me. They are t5 seal beams also have t5's on my 62 caddy and they are dim also. Should I switch to a newer seal beam or could it be something else? I appreciate any advice. Thanks

[mopar346]

Could be a ground, could be a voltage regulator or alternator, especially if it gets brighter with RPM. Could be corrosion in the wiring.

[click]

1st guess is replace the regulator with Wels VR715 , less than $10 and original old black cap fits over it... see if that helps, then dig into grounds and alternator. Grounds are most likely part of the problem in these old cars, use a box of star washers under ground strap bolts, that helps alot.

[KurtS]

Before you start replacing things, check the voltage at the light with a voltmeter. What does it read?

[1967RSxxx]

Thanks for the tips. I'll give them a try.

[77thor]

It sounds like low voltage to me.

[KurtS]

It sounds like low voltage to me.

Possibly. But that's why you measure first, then fix.
It sounds like they could be the original T3 headlights, which aren't bright after 40+ years.

[69 4 Speed]

check the voltage at the light with a voltmeter. What does it read?

What should the voltage be? At idle? At 2K rpm?   I think that a lot of us have the same problem and I have up graded my lights with the best Sylvanias that I could buy.

[JohnZ]

check the voltage at the light with a voltmeter. What does it read?

What should the voltage be? At idle? At 2K rpm?   .

A voltmeter across the battery terminals should read 12.4-12.6 volts with the engine off, and should read 13.5-14.2 volts with the engine running at 1000 rpm. You shoulldn't see more than one volt less than that at the headlight connector. Clean the connector terminals and make sure the grounds are clean and shiny.

[Petes L48]

FWIW, this was linked in on a dim headlight discussion, I believe over on the TC site.  Found it interesting but I'm no electrician and have no idea on content accuracy.  Also not an option if you're running a purely stock setup: 
 
http://www.madelectrical.com/electricaltech/brighter-headlights.shtml

 

[KurtS]

I worked with OEM alternator design and wiring for many years.
What they are doing makes sense. The power is coming directly off the junction point, instead of having to run to the dash wiring, the headlight switch, and then back to the lights.

But whether it is required comes back to my initial request: what's the voltage at the headlights?

Btw, the alternator voltage varies as a function of temperature. The battery wants higher voltage (max 14.7) at low temps, lower voltage (min 13.5) at higher temps.

[Kelley W King]

Don,t forget the headlight dimmer switch and it,s terminals. They are in a perfect place to corrode.