Why were headlights adjustable?

[76 Caddy]

I had to change a headlight on the '76 Seville this weekend and it got me to wondering, "why were headlights adjustable" prior to the late eighties when autos switched to where you just change the bulb and there is no adjusting.

Tried Google but no answer, just how to adjust.

 

Tim

[m-mman]

Headlights have always been adjustable(!)  . . . well maybe not acetylene. . . . 

Imagine a flashlight where you cant move the beam? You have to direct the "brightest" part of the beam to illuminate the most important thing you want to see. 

 

There have long been screws or mechanisms to adjust the bulb/reflector/assembly to place the focal point of the beam on to the highway correctly. There are adjustments on my 1929 Cadillac (move the whole assembly) my 1926 Lincoln (lever on the steering wheel) and every sealed beam since 1940 (including the square ones in the 70s & 80s) has had two screws (mounted to the side and top) that moves the bulb side to side and up and down. 

 

Even modern cars have adjustments. Open the hood and you will find a bubble type level as part of the assembly. But with all the ultra bright blue lights blinding me in my mirror, I know that too few people properly adjust their's

 

There are state laws that describe how headlights should be properly adjusted - straight ahead, hitting the ground approximately "stopping distance" in front of the car, but NOT shining into oncoming drivers. (the left beam shines a little to the right) High beams shine higher up a farther out. 

 

Adjusting headlights was once big business. A service performed at all repair shops. Search headlight adjusting tools and you will find many varieties. Most used bubble type levels and mirrors to accomplish the task, but there was also a screen that is put up in front of the car and the beams are  aimed to what hits the screen. 

Annual state vehicle inspections checked (and failed) many a car for bad headlight adjustment. 

 

I dont think enough restorers properly adjust their lights after a restoration. I have the old adjusters and it makes a big difference when your lights are properly adjusted. 

[Frank DuVal]

Right! Getting that "hot spot" out of incoming driver's eyes is very important. So is seeing far down the road with the brights on. Our left hand drive cars are optically made to favor shining right. People make the mistake of ordering special lights from Britain and then discover they are optically favoring the left, so the spot cannot be adjusted correctly. Or they are in a non-inspection state and just don't give a *^&*%!🤣

[60FlatTop]

On a mid-'70's Caddy, with those long screws in that brittle plastic block, you're just lucky to get the bulb to stay in much less adjust it.

 

 

 

[TexRiv_63]

3 minutes ago, 60FlatTop said:

On a mid-'70's Caddy, with those long screws in that brittle plastic block, you're just lucky to get the bulb to stay in much less adjust it.

 

 

 

During a long history with 60s and 70s GM cars I learned to always have a few of those adjusters in the glove compartment, needed them on just about every car.

[Restorer32]

As late as 1937 Bentley mechanically dimmed headlights using a solenoid inside the headlight shell that literally tilted the reflector when activated.  

[CHuDWah]

Until the late-30s or so, most cars had bulb and reflector headlights with the bodies bolted to bars, stands, etc.  Given that and the rough roads of the time, something could eventually work loose enough to affect the aim, necessitating readjustment.  The Model A Ford (and probably others) service manual has a detailed adjustment procedure including diagrams and measurements.

[joe_padavano]

3 hours ago, 76 Caddy said:

I had to change a headlight on the '76 Seville this weekend and it got me to wondering, "why were headlights adjustable" prior to the late eighties when autos switched to where you just change the bulb and there is no adjusting.

 

Headlights are adjustable because that's the only way to properly aim the beam when it is changed due to manufacturing tolerances. First, the locating bosses on the lamps don't control the location that well, and the location of the filament inside the reflector is subject to positional tolerance. Add to that the tolerance of bolting the bucket to the core support, and the rubber-mounted core support to the frame, and common sense tells you that adjustment is mandatory. Of course, since it is common sense, that's why you can't find it on the interwebs. Oh, by the way, even headlights in brand new cars are adjustable for the same reason.

[TAKerry]

3 hours ago, 60FlatTop said:

On a mid-'70's Caddy, with those long screws in that brittle plastic block, you're just lucky to get the bulb to stay in much less adjust it.

 

 

 

Almost identical to the adjusters on late 70's firebirds/trans ams.

 

Also, I am pretty sure I read somewhere that with the new style headlights that adjustment was complicated, and that the state (MD at least) had taken headlight adjustment out of the inspection requirements.

[joe_padavano]

1 hour ago, TAKerry said:

Also, I am pretty sure I read somewhere that with the new style headlights that adjustment was complicated, and that the state (MD at least) had taken headlight adjustment out of the inspection requirements.

 

I can't imagine how adjustment can be any more difficult. Sure, sealed beam cars have two simple phillips screws on each bulb, but every vehicle I've ever worked on with composite headlights has similar adjusting provisions for the composite lamp housing. Typically it's a Torx head fastener or similar device that drives a gear mechanism that moves the whole housing.

[Frank DuVal]

4 hours ago, TAKerry said:

Almost identical to the adjusters on late 70's firebirds/trans ams.

Just a few different plastic nuts and several lengths of screws covers 90% of GM cars from the late 50s till they did away with sealed beams. I do not know about the Savana Van, that was the last vehicle to use sealed beams, up into the 2010s!

 

One type looks like a license plate plastic nut, another is like this:

 

[Bryan G]

Back in the days before composites my Dad bought some aiming equipment made by Hoppy as I recall. It was just complicated enough that nobody ever used it; at one time they had adapters to fit the newer lights. You lined up a plate with the 3 points on the sealed beam, then the unit itself stuck to the glass with a big suction cup. They had little lenses with mirrors inside and when everything was just right I think you would see a line in the mirror in just the right spot, or some such. Usually we just aimed them at the inside of a garage door and called it a day. Later I worked in the office of a place that did state inspections and that was still part of the requirements as of about 6 years ago. Every so often a car would come in that simply wouldn't aim and the whole unit had to be replaced. The newer units are precision, mounted on a track attached to the floor. Not cheap. There are some higher end model vehicles now that self-adjust but most still require some twiddling to get right.

[TAKerry]

14 hours ago, joe_padavano said:

 

I can't imagine how adjustment can be any more difficult. Sure, sealed beam cars have two simple phillips screws on each bulb, but every vehicle I've ever worked on with composite headlights has similar adjusting provisions for the composite lamp housing. Typically it's a Torx head fastener or similar device that drives a gear mechanism that moves the whole housing.

I suppose its not the difficulty in doing the job but the leds in general that cast in a large area. I know mom had a Lexus with 'floating lights'. They kinda bounced all over the place, was really distracting.

[60FlatTop]

Back to the Cadillac quad rectangular headlights, for the past 40 to 50 years it has been rare to see all four parallel on both the horizontal or vertical plane. There is always at least one cocked out of place.

[76 Caddy]

Maybe my original post wasn't really clear.  I know the reason why headlights are adjustable, I was just wondering why the housing the headlamp goes in (the part with the two screws and spring) wasn't permanently fixed at factory so the lights would always shine straight and level.

 

Just curious.  

 

Tim

 

[Brass is Best]

On 9/13/2021 at 12:33 PM, m-mman said:

Headlights have always been adjustable(!)  . . . well maybe not acetylene. . . . 

Imagine a flashlight where you cant move the beam? You have to direct the "brightest" part of the beam to illuminate the most important thing you want to see. 

 

There have long been screws or mechanisms to adjust the bulb/reflector/assembly to place the focal point of the beam on to the highway correctly. There are adjustments on my 1929 Cadillac (move the whole assembly) my 1926 Lincoln (lever on the steering wheel) and every sealed beam since 1940 (including the square ones in the 70s & 80s) has had two screws (mounted to the side and top) that moves the bulb side to side and up and down. 

 

Even modern cars have adjustments. Open the hood and you will find a bubble type level as part of the assembly. But with all the ultra bright blue lights blinding me in my mirror, I know that too few people properly adjust their's

 

There are state laws that describe how headlights should be properly adjusted - straight ahead, hitting the ground approximately "stopping distance" in front of the car, but NOT shining into oncoming drivers. (the left beam shines a little to the right) High beams shine higher up a farther out. 

 

Adjusting headlights was once big business. A service performed at all repair shops. Search headlight adjusting tools and you will find many varieties. Most used bubble type levels and mirrors to accomplish the task, but there was also a screen that is put up in front of the car and the beams are  aimed to what hits the screen. 

Annual state vehicle inspections checked (and failed) many a car for bad headlight adjustment. 

 

I dont think enough restorers properly adjust their lights after a restoration. I have the old adjusters and it makes a big difference when your lights are properly adjusted. 

 

Sure you can adjust acetylene. Open the valve a little and the light is dim. Open the valve a lot and burn down your car. You can also adjust the forks.

[Frank DuVal]

4 hours ago, 76 Caddy said:

wasn't permanently fixed at factory so the lights would always shine straight and level.

Well, they had to be adjusted once built, so why take the adjusting mechanism out?🤔

 

Variations in shims used to get hoods to line up with fenders to line up with doors makes no two GM cars of that era the same in how the radiator support (mounted on rubber bushings) is in relation to the ground.

[Bryan G]

8 hours ago, Frank DuVal said:

Variations in shims used to get hoods to line up with fenders to line up with doors makes no two GM cars of that era the same in how the radiator support (mounted on rubber bushings) is in relation to the ground.

I well remember seeing a mid-80s Fleetwood with almost an inch of shims between the left fender & cowl...and maybe one shim on the right side. Yes, from the factory. 

[bryankazmer]

6 minutes ago, Bryan G said:

I well remember seeing a mid-80s Fleetwood with almost an inch of shims between the left fender & cowl...and maybe one shim on the right side. Yes, from the factory. 

And that's how you go from 60% market share to 20%

[Terry Bond]

On 9/13/2021 at 2:28 PM, Restorer32 said:

As late as 1937 Bentley mechanically dimmed headlights using a solenoid inside the headlight shell that literally tilted the reflector when activated.  

Our 1935 Morris has those mechanically dipping headlamps.  Powered by Lucas of course.

Terry