The issue of the correct level of voltage getting to various interior light bulbs is important. When the cars were new, the interior and cluster lighting was "normal", with the map light in our '66 Newport being bright enough to read a map at night with no issues.
With time and use, dust can migrate into areas of the instrument cluster and the reflectors of other interior lights to dim their effective output by a noticeable amount. Another issue is the condition of the reflectors! When new, they were shiny and "chrome-like", if not chromed. But 50+ years later, much dust migration can happen, by observation. Especially in areas where it is uncommon for vehicle to have had factory-installed air conditioning, where "windows down, cowl vents open" was more common most of the year.
Combine this with dust also settling in on the insides of the related lenses and less actual light output. NOT to forget that some of the lenses have yellowed a bit with age and heat.
SO . . . cleaning and refurbishing the reflector area of the lamp, plus wiping any dust off of the bulb and inside of the lens are first steps. Then comes the voltage checks, if needed, which can possibly result in an investigation of the wiring harness related to the lights themselves. Then the rheostat in the headlight switch itself. Which can then lead to the bulkhead connector's terminals. Which can then lead to the vehicle charing system.
In most cases, things on the output side of the headlight dimmer can make things better. Just as making sure the charging system (alternator, battery, and related cables) are doing what they are supposed to can be the next obvious checks. IF a prior owner or similar has made any modifications to the harness for added equipment, THAT can become part of the mix too.
It seems to be "trendy" now to automatically perceive that adding LED bulbs into the mix is a quick fix, which it can be, BUT if there are other issues at play, they can be an expensive-to-me Band-Aid fix. LEDs can also be an indication of other vision-related emerging issues, from my own experiences. Reasons why older people are usually at home after sundown, other than for potential personal safety issues. Whether in the 1970s or now.
End result, having instrument panel lights that are "too bright" can decrease the ability to see down the road, in the fringe areas of a vehicle's headlight beams in the process. What is more important, seeing the speedometer at full LED brightness or that deer "in the shadows" in the bar ditch that will be frightened by your vehicle, as you're driving 60+mph on a dark highway? Personally, that incandescent-lit instrument cluster at 70% max brightness can be the best option, to me. PLUS making sure the headlight bulb lenses are ALSO clean!
Just some thoughts and experiences,
CBODY67
Take the lens off, make sure it's clean inside the housing so it will reflect the light. Make sure the lens is not painted inside to dim the light.
Remove the bulb, what number is it? Jump power and ground to it. Does it get any brighter or stay dim?
Check for battery voltage at socket.
Check resistance to ground at bulb contact. The ground is switched by the jamb switches so it's on a terminal at bottom of socket, it is not a chassis ground on base of bulb.
Do you have a volt meter?
Just wanted to add to this - I had my tail light housings apart, and just out of pure curiosity rubbed a bit at the reflector, and saw the amount of dust left on my thumb, and a very shiny thumb-shaped spot. I wish I took photos of the before and after, just by rubbing it with nothing but a cloth it was a lot shinier and probably improved light output a bit.With time and use, dust can migrate into areas of the instrument cluster and the reflectors of other interior lights to dim their effective output by a noticeable amount
Buy a multimeter - even if you don't do much electrical work, a somewhat entry-level/cheap one can let you do a decent amount of stuff. People will also think you're a wizard when you learn how to use one to diagnose electrical problems. Also great around the house, as well as computers if that's up your alley.I'm not too electrical-savvy, how do you do those last 2?
Meters? We used to term them "VOM" for Volt Ohm Meter. Measures voltage on a few scales. Same for Ohms (resistance). Most have a continuity checker/beep, too. Can be quite useful.Just wanted to add to this - I had my tail light housings apart, and just out of pure curiosity rubbed a bit at the reflector, and saw the amount of dust left on my thumb, and a very shiny thumb-shaped spot. I wish I took photos of the before and after, just by rubbing it with nothing but a cloth it was a lot shinier and probably improved light output a bit.
Buy a multimeter - even if you don't do much electrical work, a somewhat entry-level/cheap one can let you do a decent amount of stuff. People will also think you're a wizard when you learn how to use one to diagnose electrical problems. Also great around the house, as well as computers if that's up your alley.
Meters? We used to term them "VOM" for Volt Ohm Meter. Measures voltage on a few scales. Same for Ohms (resistance). Most have a continuity checker/beep, too. Can be quite useful.
You can spend $25.00 or over $250.00, depending upon robustness of construction and number of scales measured. Aim toward the lower level, for general use. I bought mine at Radio Shack in the 1990s, when they were still around.
CBODY67
View attachment 694137
This is a volt, ohm meter. Take the ground lead and put it to ground and the bulb socket with the other lead while on the volt scale