Any help for dim headlights?

[richard5933]

The headlights on my 4108 are dim. I'd venture to say that they are really dim. High beams are only slightly better than low beams.

Are there some common places to look for problems with the headlight circuit?

My goal is to keep the OEM headlights for now. Any suggestions would be most welcome.

[Gary Hatt - Publisher BCM]

You can try polishing your lenses. That will help if they are getting foggy.  Some people use toothpaste but any fine grit will work.  If you need more power, you may want to check your ground wire as it may be rusted a bit.   There are other solutions, but you should check your ground first. Maybe run a test ground wire from your battery to your light socket and see if it gets brighter. If so, the ground may be the problem.

[eagle19952]

poor ground. try a direct ground jumper to confirm.
low voltage, bad relay, usually.

[bevans6]

12v  or 24 v, and what gauge wiring to the headlights?  what are the voltages when the bus is running (alternator on) and lights are on?  Grounds? And what kind of headlights?  Old school incandescent, or quartz halogen, or new LED's?  I solved my personal crappy headlight issue with some excellent 28 volt Cibie Halogen lights.  Most times, bad headlights are voltage drop to the lights from bad grounds or too small gauge wiring, plain old worn out bulbs, or a bad 24 volt to 12 volt conversion (what I had).  Plus, what was once acceptable is now simply not, perfect old headlights now seem unusable.

[richard5933]

I'll measure and confirm voltage levels tomorrow. Same with the grounds.

There is a small panel in the tool compartment under the driver which my manual indicates is the mounting place for the lighting circuit breakers. Would this be where the relay is as well? Or, is there one in the electric panel to the left of the driver?

Headlights currently in the bus are the OEM 24v sealed beam headlight. Wiring is stock. I don't know the gauge off hand. Plugs on the back of the bulbs are tight and clean. I'll have to track down the ground contacts tomorrow.

[eagle19952]

Headlights currently in the bus are the OEM 24v sealed beam headlight. Wiring is stock.

which allows for smaller wire.
I would also check the resistance of each wire involved.
corroded 50 year old wire can be hard to isolate.

This equation, i = v/r, tells us that the current, i, flowing through a circuit is directly proportional to the voltage, v, and inversely proportional to the resistance, r. In other words, if we increase the voltage, then the current will increase. But, if we increase the resistance, then the current will decrease.

[luvrbus]

We always solved that problem on Eagles which were crappy too by adding relays for each light.If I recall the 28v head light are 60/80 watts a drop of a 1/2 to 1 volt will make a huge difference in brightness.I saw buses before some one had installed all four lamps the same model and number on the 4 light systems it sucked on bright 

[chessie4905]

They seem dinner compared to current headlights. Take an accurate voltmeter and check voltage at headlamps before spending time looking elsewhere. Since your coach is in such great condition, I expect the option is to go with different lamps. I haven't found any led headlamps in 5  3/4 diameter out there in 24 volt. Other sizes, yes. One option is to convert headlamps to 12 volt and use halogen or led. Changing to 12 volt on Buffaloes is easy.  Where those relays are in under driver's compartment, GM had a plug and play resistor panel that enabled the option of using 12 volt headlamps. You install panel, plug it in and replace headlamps with 12 volt units.
The only question I have is that different bulbs will draw different currents affecting voltage at bulbs, especially LEDs. Probably worth a try if Luke has a take off resistor panel.
Of course, this is assuming you don't have a votage issue with current headlamps.

[bevans6]

I put in 28 volt quartz halogen lights.  The lights themselves are normal Cibie lights, and the bulbs are available from Daniel Stern.  About as good as bus lights are going to get.  That said, these look very interesting - 9V to 32V, DOT approved, these would be the high/low beams, not the high beams.  That is a very common motorcycle application, you may not find (or need) the equivalent high only beams.  https://genssi.com/5-75-5-3-4-in-led-black-projector-headlight-round-dot-v2-set/

[richard5933]

If my reading of the manual is correct, the headlights that came stock in the bus have the following power draw:
    Low beam:    37.5w / 55w
    High beam:   37.5w

I've been in touch with DanialSternLighting and they do have modern lens/housing assemblies with replaceable bulbs that will work on 24v. Sounds like they would be a drop in replacement, at least for the most part. However, the bulbs run 70w each, which is nearly twice what my wiring is designed to handle. Guess that could be handled by installing a few relays and heavier gauge wiring from the 24v power tap to the relay and on to the headlights.

My first step will be more basic - if the weather holds today I plan to pull the relay/resister panel and check all the connections, as well as check the ground connections. All the other lights (clearance, etc.) run bright and clear, so I'm hoping the problem with the headlights is just a weak connection or sticking relay somewhere.

[chessie4905]

Like I said, buy a volt meter and check voltage at bulbs before you start taking things apart. If you change to other headlights, go with led. They are far brighter and draw less current.

[luvrbus]

LED's are nice for the driver but suck for on coming traffic and coming up behind you,some states are cracking down on those, here you get a repair ticket with so many days to dim the lights and I like that in the desert a little light goes a long way

[richard5933]

The problem I see with LED as an option is fitting them into the existing buckets. The sealed beam lights are fairly shallow, and the LED lamps look like they carry quite a bit of junk in their trunk.

The issue with LED lights and blinding oncoming cars is that most of them are not actually approved for on-road use. They are available in formats that do not blind other drivers, but those are much more expensive.

My first plan of attack will be to fix what I've got. If I can make them work like properly functioning sealed beam headlights I'll be okay for now. I drove with them for decades on cars with no problem. We rarely drive the bus at night, so getting the current setup working should suffice for now. If not, I'll explore other options.

Voltage readings hopefully will follow later today.

[luvrbus]

Voltage plays a huge parts those lights are rated at 28 volts for full brightness,they are supposed to sell the LED's by the lumen but skirt around that and tell you the watts.I bought a pallet full of LED's (7in) from a military sale it took me for ever to sell those @ 10 bucks ea because they were 2000 lumen and not legal for hiway use     

[Fred Mc]

After doing the research and then the installation of solar panels I have become acutely aware of the importance of having the correct size wire for 12/24 volt accessories. Prior to that I never gave wire gauge much thought. But having under size wire can make a huge difference especially with lights.  Of course, with the bus wiring being 50 years old condition of existing wiring should also be suspect.