Going over Craig's (grumpydogs) web site, I saw where he wired his 12 volt clearance lights in series so they would work on 24 volts. Can this be done with the headlights? Thanks Tomas
Can be, should not. Every effort has to be made to make the headlights as reliable as possible. If they are wired in series and one burns out, the other would follow rather quickly. And you know that would be exactly the time your in the mountains on a narrow, windy road with no lights around. Need I say more? Good Luck, TomC
In fact, if one burnt out the other would stop working instantly because there would be no power to it. Having said that, haven't I read that some MCI headlights are 12v wired in series? If for some reason you have to use 12v lights then you could use a step-down transformer (commonly available so truckers can use 12v stereos and other 'car' gadgets), or you could take a central 12v tap off your battery, and wire the 24v from the headlight switch so it operated a relay on a 12v circuit.
Jeremy
MCI's are wired so as to have a 12V backup to keep the other lite working if one fails. Jerry
Search the BB for the MCI 12 volt wiring diagram, Another choice is to run the headlights (or all the exterior lights) of the 12 volt battery terminal with a Vanner equalizer maintaining equal voltage on the batteries
on my 4905 they are wired series/parall el and on my mci they are 24 volts. They use a relay that will let 24v work in series with the low beams and them series/parallel on high beams. as stated when one burns out u r n the dark. If you tap the 12 v from the 24v and run a lot with lights on you will not have proper charging to the battery and will burn one of them up since you will pull a bigger load off one instead of two. You can get a step transformer to help that tho and that is what I would recommend
on my mci-8 they are 24 volts ??? Gomer
We now have two posters who know where to get transformers that work on DC. There are DC to DC converters, dropping resistors and package regulators, but DC transformers are impossible.
gomer: The Vanner equalizer is used by bus manufacturers and most converters who have 24 volt systems to eliminate the problems that you describe. If you have have a headlight system wired so that if one burns out, you are in the dark, it should be changed to one that works properly.
that is what I was trying to think of VANNER thanks again for that info gomer
It's my understanding that MCI has had a bulletin out since way back... some time in the '80's about this. My '78 MC-8 has its headlights wired in series with diodes and the center tap (12V) to keep 'em working if one burns out. My headlight bezel even has '12V' stamped on it to prevent confusion.
David
Tomas - my bus has a DC to DC converter to run the headlights. It was part of the R&M headlight upgrade kit. My bus has the VR24-1220 (Info here: http://www.transpo.de/cgi-win/product.exe?VR241220)
For more information on other choices go to: http://www.transpo.de/Catalog/Browse.htm
On the left side, scroll through the product categories and choose the DC/DC Equipment category (last in the list). This action will cause another box to appear under the categories box.
In the new box, select VARIOUS. This will bring up a product list.
Scroll down until you find the part numbers VR24-1220 and VR24-1224. Looking at the device specs, I gather that VR24-1220 translates to "Voltage Reducer" 24 to 12 volts, 20 amps continuous. The VR24-1224 is 24A continuous. My bus has the VR24-1220 and works fine with my 4 rectangular headlights. The 24A might give more insurance.
Mine is wired with switched 24v from the headlight switch powering the converter. The converter feeds the low beams, and the high beams via the dimmer switch.
This unit was part of the R&M conversion kit at the time; can't say if it is still that way.
Craig - MC7 Oregon
Ask Dex (http://www.dexknows.com/) nuthin'. Ask Chuck instead! ;):
http://busbuilding.com/bus-conversion/mci-headlight-wiring-12-volt-lights-on-a-24-volt-system/
MC9 headlights are 12v bulbs wired in series on 24v system. There is a 12v backup wired in between the two bulbs. This system works great, if someone who knows more than MCI hasn't mucked with them. Absolutely, it is a good way to put 12v bulbs on a
24v system, without the expense of transformers, converters, heavy duty switches, breakers, etc.
As for the clearance lights, I'm not recommending that any longer with LED lights. Nearly all of mine have burned out, and until I can figure out if they were just plain cheap junk, or it was a result of series wiring, I'm not recommending it. I'll be changing them out this fall and running them off 12v. Will then see if I have as many die as I did before.
craig
gumpy: Series wiring will only work with identical bulbs. Otherwise, one bulb gets high voltage and one get low voltage.
If you have a heavy wire (#4 or even #6) from a Vanner equalizer to the front junction box, it is easy to put in a 12 volt bus bar and connect all the exterior light breakers to 12 volts. None of the switching needs to be changed but you need to change to a 12 volt signal flasher. If you have current relays to sense brake or signal bulb failure, you have to adjust the relay for the higher current at 12 volts. They cannot be adjusted low enough for LED lights.
Most here don't understand MCI's system . They actually us the center of the 12 V batteries in series to stabilize the voltage for the series headlites so even if the bulbs are mismatched they still get the proper voltage. Jerry
Quote from: Jerry32 on July 16, 2007, 07:28:30 PM
Most here don't understand MCI's system .
Boy, there's the understatement of the decade.
If they did, you wouldn't get people telling you it can't be done, and won't work.
My headlights had been mucked with prior to my purchasing the bus. Left me in the dark on a deer infested highway one night at 0-dark-thirty. I wired them back to the original schematic. Haven't had a bit of problems with them since, except when I hit those two deer last December. Shattered one low beam bulb, but gosh, the other side continued to shine as if nothing had happened. Someone must have forgot to tell that bulb it couldn't continue working without it's partner.
I didn't have to change any breakers, readjust any relays (whatever the heck that means), or increase the size of the wires. All I did was move the diodes and breakers up out of the moisture of the steering compartment.
Why anyone would want to change from a tried and proven system is beyond me, but it happens all the time, and there are several on this board who seem to think they know more about MCI engineering than the engineers at MCI who designed the system.
I just don't get it.
gumpy: Sorry if I wasn't clear. You said that you didn't understand why your series clearance lights all failed so I gave you a possible reason. BTW: Does your bus indicate when you have a bulb failure on the brake and/or signal lights? That may be an option but I thought it was standard on MCI from way back.
Quote from: Stan on July 17, 2007, 05:17:06 AM
You said that you didn't understand why your series clearance lights all failed so I gave you a possible reason.
Well, the lights are all the same model by the same manufacturer, so in theory, it should work just fine. In reality, though, they worked for a few months, and then started burning out. Not many have survived, and I have not been able to ascertain if it's due to the series wiring somehow, or if it's just that the lights are junk.
I'm going to replace them with more of the same, but this time I'll run them off the 12 volt output from my toad converter. Will see how long they last.
[quote/
BTW: Does your bus indicate when you have a bulb failure on the brake and/or signal lights? That may be an option but I thought it was standard on MCI from way back.
[/quote]
Not that I'm aware of. If so, this is the first time I've heard of such a thing on any MCI. There is one indicator light in my panel that is not marked, and I can't figure out what it is, but it's not lit, so I guess it's a possibility. Anyone else ever hear of this?
Craig: You should have a dash light that comes on when the service brake is applied and another one that is the signal light indicator. Try removing one exterior bulb and that indicator should not light if your MCI has that bad bulb feature. Tracing out the wiring diagram would show the current to the bulbs going through the coil of a relay instead of the contacts. If you have that, it is a current sensitive relay that can be adjusted to turn on the dash light when both brake bulbs (or three signal bulbs) are working. If one bulb is burnt out, there would not be enough current to pick up the relay.
I thought that this circuit was standard on MCI, at least up to the MC-9 series, but maybe not. HTH
Craig and Stan,
I had a problem with my brake light relay in the RJB last year, so I can personally attest to the fact that if you have a brake light out then the "STOP LITE" Tell-tale will not light up. It is also true that if you burn out a turn signal that will not light as well.
As for the marker lights, I don't know of any system that will warn you. Yet...
My 1980 MC-9 is wired as an MC-8 so I don't know if Craig's has been updated or not.
I can't use the maint. manual from the 1989 edition to chase anything from my Rear Junction Box.
FWIW
Devin
Devin: There is no warning system for the running lights. With all the different bulb currents and people not using the exact replacement it would be a nightmare to keep it working. It is not as critical as the turn signal and brake lights unless you have a bunch not working.
The Tell-Tale system you have was in use from the early MC-5 around 1960.
I think Devin has an early 9. I just went out and got my book, because I was pretty sure there were no relays in the MC9 tail light system, and sure enough, the schematic shows no relays. I think this is something that was in the earlier models possibly up through the MC8, and into the very early MC9s, and was then removed.
I think I have a manual at home which is more inclusive of all models, and shows the various schematics and the models they apply to. I'll try to remember to look at the early schematics when I get home in a few weeks.
Craig: If you have the relays I referred to, they will be the ones that turn on the Brake and Signal Light Tell-Tales. Instead of having one wire to the coil and one to ground, the coil is in series with the respective lights.