12 volt series headlights?

[Stan]

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.

[gumpy]

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?

[Stan]

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

[Devin & Amy]

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

[Stan]

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.

[gumpy]

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.

[Stan]

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.