Run 12 volt lights in 24 volt coach in series?

[scanzel]

Not all leds run on 10 to 30  dc. If you look at some of ones out there Trucklite, Optronics, Grote they have 12 and 24 units available. Most 12's I see are good to 14v, 24v good to 30v. Be carefull it can become costly when you flip the switch and they all burn out at once. My interior system is all led but some are 24v and others 12v because I could not find the ones I liked in 24v.

[Jcparmley]

Hi Scott

did you ever figure out your LED light issue.  I have a MCI 102c3 as well and looking at the wiring schematic I believe the headlights and the taillights are 12 volt.  Am I wrong?  What about the marker lights on the roof?  Are they 12 or 24?  My hope is they are 12 also.  Thanks

Ok. Thanks. I'll choose LED's accordingly


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[Jim Blackwood]

LED technology is getting better but there is still a lot of junk out there. The problem is that automotive voltage levels are nowhere near as tightly regulated as the raw LED needs. For instance, a 12v system can hit 17v under some conditions and 15v is not uncommon. So an LED optimized at 12v can draw 25% more current and they just aren't built to dissipate that much heat so they burn out. Incidentally, most diodes conduct when burned out (equally in both directions) so if you burn out one of a series pair then yes, it is likely the other will burn out too. The voltage drop of a single LED is low, something on the order of a volt and a half. To get these new bulbs that can run directly on 12v they are arranged in a series and sometimes a series/parallel matrix sort of like your battery cells. Because the operating voltage is built up in a series of discrete steps, and because LEDs are kinda critical about the current they have to have to put out their rated amount of light and not melt down, it's extremely hard to build a bright light which includes adequate over-current protection. And if an individual LED goes over current it dies immediately. Then that cascades.

Several approaches have been tried to remedy this, some successful, some not so much. It's best to stick with the proven products and do whatever you can to tightly regulate your vehicle voltages.

Prof

[richard5933]

I've got LED bulbs in use in many interior lights in our bus. I had 24v bulbs or a while, but have since switched the interior lighting totally to 12v and have changed the bulbs.

Exterior lighting (chassis lighting) is all 24v on our coach. I've decided not to switch to LED due to possible problems with voltage as well as problems with things like turn signals not working properly.

The only LED lights that I've added to the 24v chassis lighting are the two new license plate lights. When I installed the Jake brake bump I installed LED lights that double as license plate mounting bolts. The only ones that I could find were the 12v units, so I installed two of them in series and connected them in parallel to the factory license plate light. So far so good.