Head Light Issues

[Jim Eh.]

Why MCI would ever use 12V headlamps in a 24V system I will never know. I had a wiring issue in my MC12 and converted over to LED. Now I am definately NOT a fan of running aftermarket LED headlamps but in this case I went the easy way and installed them rather than burning out a bunch (more) 12V headlamps. I tried installing a new incandescent low beam on the right side as it was definitely burnt out. What I did not know was the cause of it and consequently, burnt a brand new one out. At this point I ordered a set of LED lamps as they could handle the 24V without damage while I sourced the issue.
What I ended up doing was I removed the common ground(?) off the left hand set of headlamps from the diode and ran it to it's own ground. Now I believe this will supply 24V to all headlamps but like I said,being LEDs they can handle it. I even had a spare keyed power to run through a switching relay to have Daytime Running Lights operational (something that is required up here).
Not sure if it will affect any other system but it worked for my 5 hour test drive.

[richard5933]

Didn't MCI have their system setup so that two 12v headlight ran in series on a 24v circuit?

I researched this quite a bit when I was working on my dim headlights. Couldn't figure out why GM has started using 12v lamps when the bus was 24v. The answer was really simple - 24v lamps were becoming a rare item in the automotive world and they just switched to what was the standard at the time. That standard was 12v incandescent headlights.

I did find and buy a set of 24v lamps before I realized that my bus had the 12v conversion on it. The packaging for them is marked 'not for highway use'. Don't think you'll easily find DOT approved 24v lamps anymore.

GM ran the 12v lamps by using a resistor bank to convert to 12v. That's where my problem was. I removed the resistor bank and installed four 24v-to-13.8v converters. I went with these:

https://www.amazon.com/gp/product/B01LY8D7U0/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Yes, they are oversized for my needs. Since I always figure it's best not to run things like this at/near capacity I went with the biggest that could comfortably be installed in the space allotted. They run much cooler that way and will last longer.

My headlights are MUCH brighter now, for sure. I used the 13.8v output since that's the optimal voltage for things like headlights. I think that many make the mistake of using a converter with a 12v output, which is really too low to run a 12v headlight at full brightness.

Picture below is what the panel looks like before/after.

On my GM bus, this wasn't really that difficult to install since each headlight in the quad system has its own supply coming to it from the main panel. Looks like they engineered the system so that if a circuit was to fail only one of four bulbs would be taken down.

If you run LED bulbs, be careful which ones you choose. Many of them are horrible, both in the light they produce and in blinding oncoming drivers. The light doesn't get focused on the road where you need it, instead scattering it all over the place.

[chessie4905]

Just get a quality lamp and put in leds and forget all the complexity. Hella makes great lamps with renowned patterns. Especially if you do significant driving at night. Many of the appropriate bulbs work from 12 to 30 volts.

[Jim Blackwood]

That doesn't really work. The LED headlamp optics have to be engineered for the LED hot spot. It is not the same as an incandescent or halogen. The hot spot can't be the same because it takes more room so it is more dispersed, meaning the light will be more dispersed.

Jim

[Lin]

We replaced the original 24v headlights with Hella fixtures and 24v bulbs.  They work fine.

[chessie4905]

Techanically, you are right. Real world results; they work fine, especially sitting that far above the lamps.

[luvrbus]

MCI used a 12V center tap between the two batteries (24V) for the head lamps and it wasn't a great idea 

[richard5933]

Techanically, you are right. Real world results; they work fine, especially sitting that far above the lamps.

I've seen some real-world tests results, and while things might initially look good and bright from in the driver's seat, the problem from the unfocused light is that it generally doesn't project far enough down the road, and if it does it comes with too much scattered light in the foreground which makes distant sight more difficult.

And that's not even touching the consequences for oncoming drivers blinded by your headlights.

Here's a nice video from a guy doing a 4106 showing all the testing he did before choosing an LED for his bus. Not as simple as one might think to choose.

https://www.youtube.com/watch?v=ZGOJHUtWRvE

I think that the difference in the ones with a proper top cutoff and the ones without is astounding. No wonder the cheaper lamps blind oncoming traffic.

[chessie4905]

Good bulbs, proper adjustment alleviates most issues. If you have drivers giving you the high beams, they need adjusted  lower some. I prefer to get some warning of deer crossing here at night. Also wet roads at night doesn't help either.

[richard5933]

Good bulbs, proper adjustment alleviates most issues. If you have drivers giving you the high beams, they need adjusted  lower some. I prefer to get some warning of deer crossing here at night. Also wet roads at night doesn't help either.

Agree 100%

The problem is that many of the LED headlamps being sold right now don't focus the light output enough to aim anything, as they just scatter it around. In the video I linked to earlier Juan went through a few varieties before finding one that was able to be aimed.

If you look at nearly any LED headlamp in a NAPA or other auto store, you'll see where they are marked 'off road use only' because they are not DOT approved. Usually there is a reason.

[chessie4905]

Thats not a problem around here.Nobody would reject a Hella headlamp. Not even inspection stations. Too many other things to check. Unless there are large black letters across the lens...

[luvrbus]

 I bought a pallet of these at a Military auction they don't have LED's at the top of the blub,they are plug and play for most military vehicles since they are all 28v   

[Jim Eh.]

I used "DOT" stamped units. Not that knock off are ever counterfeit stuff but at least it says DOT. They are multi position. The only downside that I never thought of is that they have plastic lenses. I will be clear coating them before too much service. As I do not plan on excessive night driving (and I am half blind anyway) they should suit my needs perfectly.
The big issue was the cost (relatively cheap) and they can handle 9 - 30 volts that allowed me to source my circuit issues.

[luvrbus]

I used "DOT" stamped units. Not that knock off are ever counterfeit stuff but at least it says DOT. They are multi position. The only downside that I never thought of is that they have plastic lenses. I will be clear coating them before too much service. As I do not plan on excessive night driving (and I am half blind anyway) they should suit my needs perfectly.
The big issue was the cost (relatively cheap) and they can handle 9 - 30 volts that allowed me to source my circuit issues.

Jim 3 M diamond shield is a better option then in 4 or 5 years you peel it off and replace it stops the rock and gravel chips too, I find clear coat will yellow on plastic   

[chessie4905]

At least some of the Hella bulbs, if not all, have glass lenses. Also available on Amazon.