Are 12V Headlights Normal on MC9?

[Gary Hatt - Publisher BCM]

I recently purchased an MC9 which was registered and in use.  I have problems with most of the exterior lighting.  The headlights are a disaster, on High Beam two lights illuminate on one side, one of them very dim.  The other side only one headlight illuminates. On low beam, one light just barely lights up and the other side, nothing.   I assume on high beam both headlights should illuminate and on low beam, I assume the outside lights should illuminate.

I removed the headlights and discovered there were all 12V sealed beams.  I get a reading of 24V on one lamp socket and about 4-6V on the rest and 0V on one socket.  I haven't tested it out yet, but obviously something is really messed up.  Some of the sockets are pretty dirty, but I got a reading from the wires themselves.

Before getting into this mess, are 12V bulbs normal for an MC9 or should be they be replaced with 24V bulbs?

As far as the tail lights are concerned, when pushing on the brake peddle, the bottom set of the 3 light pattern illuminate.  One directional light works, but the large taillight in the middle never illuminates.  What is the correct pattern for lighting in the rear?  I removed the bulbs and every bulb was a different part number.  Is every MC9 such a disaster or did I just get "lucky" buying a bus from an un-reputable dealer? 

Gary

[Sean]

Yes, MC9s have 12v headlights.  There is a fairly complex relay setup to run the four 12V lamps from the 24V supply, with an extra line from the battery center tap.  Effectively, the lamps on one side run on the "lower" 12V of the batteries, and the other side runs on the "upper" 12V,  The relays are used to turn the lamps on and off and to select high vs. low beam.  The system depends on having identical batteries top and bottom, to mediate the voltage from the charging system into exactly two halves.

-Sean
http://OurOdyssey.BlogSpot.com

[gumpy]

Sean's pretty much correct on what he said. MCI started putting 12v lights in with the early MC9s (or maybe late MC8s). They are wired in series, and typically have a relay for selecting hi/low, and a relay and diode set to provide a 12v safety to the center of the series connection. That being said, I have seen more than one that varied from that standard, and appeared to be factory. One did not include the 12v relay and diodes. The other included considerable wiring differences through the master and light switches. 

In addition to these "factory variants" many mechanics knew better than MCI engineers how to make headlights work, so it's not uncommon for an MC9 to be completely mucked up in the headlights. One typical modification is to eliminate the 24v feed, ground the left socket and try to run the headlights direct off the center tap. This usually doesn't work, and the end result is darkness as the circuit breaker trips.

Before you go "changing" things, I suggest you get a copy of the wiring schematic and do some investigative work to figure out exactly what you have, and if it's normal or has been modified. It's really not that difficult once you understand the circuit. I would also suggest you return the wiring to it's original state, including all voltages, diodes, relays, and circuit breakers. It might take a few days to get it straightened out, but you'll be very happy for many years. I did that with mine about 6 years ago, and appreciate it every time I turn on the switch.

craig

[Jerry32]

That curcuit must have been adopted for all later coaches as I know mine has it too. Works very well in series arangement with center tap backup. Jerry

[Gary Hatt - Publisher BCM]

Thanks for your help guys.  I will dig out the Electrical Diagram and see if it is wired as per the factory specs and if not, try to return it back to its original configuration.

Gary

[bobofthenorth]

Based on your description of the symptoms the first thing I'd do is clean up the grounds. 

[busshawg]

I'm with Bob, clean up the grounds. Mine were doing the same,  I cleaned up the connection bars and my problems were fixed, as per some good advice form the board. On the lower side of the drivers side front , there is an access door, it gets you into the steering components. You will have to sit right down on the ground and try to look right up to the front of the bus (near the top) and you should see some wires that are all connected to a power bar or connection strip. (not sure of the proper name) You will probably need a flash light. These connections are a pain to get at, but probably will be corroded. There is another such strip in your spare tire compartment , near the front of the bus toward the passenger side. I took these apart and cleaned, I suppose even if you soaked them down with good penetrating oil everyday day for a few days your connection might come back but cleaning and then spraying again might be your best bet. Not saying that this is what's wrong but it worked for me, plus even if it's not your problem , my guess is these connections should be cleaned anyway. You may find some so so wiring in there at the same time. Poor connections seem to destroy the wires for a little ways back. I now spray these down in the fall, spring and once though the summer.

Grant