Another look at brightening those headlights

October 1, 2015 | By Staff


In your January Mechanic on Duty column you responded to a request about improving headlight brightness for a 1940 Willys Coupe. I quote the first line of your response: “Sealed beam headlights were first required in the U.S. in 1940, so you would need to replace your entire existing sealed beam six-volt headlights with six-volt halogen sealed beams.”

As you know, stock 1940ish Willys questions don’t come up very often in Auto Restorer, and as an owner of 1939 and 1940 Willys sedans, I was very much interested in your reply. However, 1940 Willys did not have sealed beam headlights to the best of my knowledge. They had 6-volt 2320 bulbs.

I was looking forward to your possible suggestions to increase the brightness for the stock bulb configuration. I thought the reader with the initial question would have brought this situation to your attention and there would have been a follow-up in your column. Perhaps it is an indication of how few readers actually have one of these cars in stock form that there has been no apparent response.

Obviously, you can see that I value your expertise or I would not have bothered following up on that column with you. If I have misunderstood something here I would appreciate being schooled. Either way, I am looking forward to your reply.


Sealed beam headlights were introduced in the United States in 1939; became mandatory the following year and were used on American cars until 1984. Cars built prior to, and subsequent to those dates have a variety of shapes of headlights, using a wide range of replaceable bulbs. However, exceptions were made to the 1940 headlight mandate. I checked with a major Willys restorer I know and he confirmed that Willys was one of the exceptions, as well as the Volkswagen Beetle which had regular bulbs into the 1960s.

Fortunately, increasing the brightness of stock non-sealed beam headlights is not that difficult. Start your headlight brightening process by carefully removing the headlight lenses and bezels. Be very careful handling the lenses because they haven’t made them since before WWII, so it could require a fair amount of time and money to procure replacements. I keep a towel or thick pad handy to place lenses on to avoid breaking them.

Next, check the bulbs themselves to see if either has a burned or bad filament. Sometimes they will look intact but be faulty nevertheless. You can check them by gently tapping the bulbs on a soft surface to see if the filaments break up. Fortunately, six-volt headlamp bulbs are still easily obtainable.

But the most common problem with six-volt headlights is grounding. Six-volt systems require clean, bright, tight connections to be properly grounded back through the body and chassis of the car. Grounding usually is accomplished through the metal-to-metal contact of the socket to its mounting, but many hobbyists solder on an auxiliary ground wire and screw it securely to the chassis or body just to be safe.

Another big problem with old-style headlights is that the mirrors in them become dull and tarnished over time. Sometimes you can polish them with silver polish, but most of the time they will need to be re-silvered. Chrome shops and metal polishers can do this job for you, but it can be expensive. Re-silvering the mirrors in my 1939 Packard’s headlights cost $250 a few years ago, and I don’t imagine it has gotten any cheaper these days.

The final items I would check if the headlights are dim are the generator and battery and their connections. A low battery will cause the headlights to go dim when the engine is idling because the generator is not putting out much power at that point, so the headlights must rely on the battery. Make sure the battery is fully charged and healthy and that its connections are clean and tight, and then check the generator to ascertain that its output is adequate and up to specs. Finally, make sure the voltage regulator or cutout switch is functioning properly. There is no reason why your headlights should go dull if your six-volt system is clean, tight and up to specs.