Bus Battery wiring

[RickB]

Hey all,

Since I'm not sure if i turned on my headlights since changing out the batteries I'm wondering if my batteries are wired correctly.

I'm sending photo's along as well

Left Vanner lead goes to Bus on switch

Middle Vanner leads go to Fused lined to bus (30A 32V fuse) and second lead goes to front battery positive

Right Vanner lead goes to Bus ground

I am on my way to o'reilly's to find a fuse holder as this one has bit the dust.

Can any of you tell me if I hooked this up wrong and if that would explain why I'm sending 24 volts to my right headlight and nothing to my left?

RB

[RickB]

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[RickB]

picture 3

[RickB]

picture 4

[RickB]

picture 5

[bevans6]

Unless you bus has had all of the headlight wiring completely changed, the Vanner (which appears to be wired the same as mine was, so should be good) has nothing to do with the headlights.  30 amps at 12 volts will run headlights, but without enough margin for my taste.  Your era of MC-9 should have the 12 volt headlights running in series from the 24 volt bus electrical system.  The way it works is plus 24 volts to right headlamp, across to left headlamp, to ground.  Each headlight drops 12 volts in series.  Center between them is at 12 volts and is connected to "headlamp cut-off relay" located in the AC junction box (roof of front bay, drivers side.)  That relay is fed from a 12v center tap on the start batteries through a 15 amp auto-reset circuit breaker also located in the AC junction box.  In normal operation that relay passes no current, since the voltage at the battery center tap will be the same as the voltage dropped between the pair of headlamps.  If one headlamp fails normally both headlamps would go out because they are in series but the relay either supplies 12 volts to make the left hand headlamp work, or sinks 12 volts to make the right hand headlamp work.  

In your case, it seems that the right hand headlamp is getting 24 volts but is not sending it across to the left hand headlamp, but is sending it straight to ground, so that headlamp is burning out.  There are a lot of switches and relays and connections involved, the schematic is here:  http://busconversion101.com/PDF_Files/MCI%209%20Maint%20Manual%20in%20PDF%20format/MC-9%20-%20Maint%20Manual%20Section%207.pdf

page 7-44

Edit:  although it's not shown in the schematic, and since the Vanner was an option, it's quite possible that the 12 volt feed to the headlamp cut-off relay is fed from the Vanner.  I would still think it should not be, because it seems silly to have a 15 amp auto-reset breaker fed by a cheesy little 30 amp glass tube fuse when what is at stake is the whole headlight system working or not.  As noted, in normal operation there is no drain on the batteries at all from that 12 volt tap, it just sits there waiting till a headlight burns out.  I wonder if in your wiring work you removed that 12v center tap feed to the relay, or connected it to ground by mistake.  If you connected it to ground you would get 24 volts across the right headlamp and zero across the left headlamp.   Oh, and right is passenger side, left is driver side.  As if you were sitting in the driver's seat, not as if you were looking at the bus from the front.

Brian