Bus Electrical Issue

[flynbanjo]

I was working on the bus today and I noticed that most of the clearance lights will come on when I turn on the headlight switch.  The remaining light will come on only when I turn on the clearance light switch.  I am beginning to think the road relay may be bad.  Has anyone else seen this issue on a 81 MC-9?

Thanks

Steven

[Dave5Cs]

Sounds like someone wired some of them into the 12Volt system and some are still on the original 24 Volt system. Just a guess!...

Dave5Cs

[gumpy]

Sounds like that one was rewired directly to the clearance light switch, or at least to the Clearance Light side of the Master Switch (see your schematic).

Factory wiring has them in parallel on a single wire, if I recall correctly. They should all come off stud 15 in the Front Junction Box.

[flynbanjo]

I spoke with the good folks at MCI today about the headlight/clearance light issue.  They told me that it is normal for the clearance lights to come on with the headlight switch.  They said the headlight switch and the clearance light switch are wired in parallel so the headlight switch will turn on all of the other lights.  That being said, I don't remember the lights working that way before.  Maybe they have been working incorrectly for the last nine years.  Can someone confrim or deny MCI's theory that on a MC-9 the clearance lights come on with the headlight switch.

Thanks

Steven 

[flynbanjo]

Gumpy - I just reread all of the post here.  Sounds like your advice is similiar to that of MCI.  You and MCI are more likely than not correct on this issue.  I just never noticed the lights working that way before. 

[busing704]

That is the way my light on my 102 A3 turn one the C lights and they only come turn off the c lights and turn the head lights they all turn on, works for me. one other thing you can turn the c lights with the engine not running but not the head lights.

[Dave5Cs]

Maybe different on the 9. My 5C has a separate switch just for the clearance lights and 1 for the headlights by themselves.

[Stormcloud]

My '7' built in late 1972 also has 1 switch for headlights, 1 switch for all other external running lights.

[Oonrahnjay]

My '7' built in late 1972 also has 1 switch for headlights, 1 switch for all other external running lights. 

       And for a note from the "all things weird" corner, on my bus the front running lights ("parking lights") and the license plate light in the rear come on whenever the master battery switch is on.   The idea was that any time the bus was parked in the garage, anyone could look down the corridor and see if the master switch had been left on whether the bus was driven in or backed in.  Of course, if the switch HAD been left on, it meant that there were lights burning to quickly run the batteries down, but that's another story.   

[LuckyChow]

I'm on a transit property.  The headlight and clearance light switching are combined on all our DL MCI's.  This is different than it was back in the MC-9 days. 

[gumpy]

MC9 has two switches, as indicated. One for clearance lights and one for the headlights/clearance lights. Both are connected to 24v bus bar. The clearance switch
output does not run through the master switch. The headlight switch output does run through the master switch and activates the clearance lights, too.

Clearance lights can be turned on regardless of the master switch position.

Headlight switch only works when the master switch is on.

Look at the external lighting schematic in the manual. Section 7. 

http://www.buses101.com/PDF_Files/MCI%209%20Maint%20Manual%20in%20PDF%20format/MC-9%20-%20Maint%20Manual%20Section%207.pdf

craig

[Lin]

My 5a has two switches, one for headlights and one for clearance lights.  The tail lights are on the clearance light switch.