Telltales

[Lin]

I finally got around to trying to trace out and reconnect my tell tale wires.  I did find some.  Since the bus is indoors now, I won't be able to test them out for a week.  I could not find the wire for the Low Air telltale, so I guess I will go back further into the system to run one.  I did however find a wire that the book identified as the Stop Light Telltale.  Unfortunately, my telltale cluster does have have a space for that.  I placed it in the Lav Emerg space since I usually know when I have such an emergency without needing a warning light.  My question is what does the Stop Light telltale do?  I need to know so I can determine if it is working.  Right now it goes on when the switch is on, but that would make some sense since the stop lights are on when the park brakes are locked.  It also gets brighter if I step on the brake.

[HighTechRedneck]

You've got it pretty well figured out.  The stop light indicator simply lights when the brake lights are on.  Serves as a driver reminder/confirmation when either service or park brakes are set.

[Len Silva]

On my 4104, the stop telltale was operated through a current relay and so would indicate that the stop lamps were actually working. The relay had long since been bypassed so the telltale served no purpose except to tell me I was stepping on the brake (just in case I didn't know that)

The only other electrical systems I have worked on were Eagles and the telltale was just wired to the brake light circuit.  Made no sense to me why it was there, except maybe a vestige from the old days when it did serve a purpose.  I've even had people tell me it was a "requirement" from some authority or other but I could never find it.

Len

[Stan]

The Stop Light Telltale connects to a current relay. Current to the brake lights go through the relay coil. When both brake lamps light, there is enough current to pull in the relay which has contacts to turn on the Telltale. Thus, its main function is to indicate a burned out bulb or non working bulb. The Turn Signal Telltale is a similar circuit.

Your bus may not have this relay if it was not factory equipped with a Stop Light Telltale. Like cars and trucks, buses use a standard wiring harness that has all the wires for every option. If the option is not ordered, the wire for that option is just tied back.

[Busted Knuckle]

The Stop Light Telltale connects to a current relay. Current to the brake lights go through the relay coil. When both brake lamps light, there is enough current to pull in the relay which has contacts to turn on the Telltale. Thus, its main function is to indicate a burned out bulb or non working bulb. The Turn Signal Telltale is a similar circuit.

Your bus may not have this relay if it was not factory equipped with a Stop Light Telltale. Like cars and trucks, buses use a standard wiring harness that has all the wires for every option. If the option is not ordered, the wire for that option is just tied back.

Well put Stan, I was going to say pretty much what you did. As this is my experience with MCI's. Now on my Setra's on the other hand if the brake/stop light  tell tail lights up it means you have a defect! FWIW   BK 

[Stan]

BK: I don't understand your response. Do you agree with what I posted or are you saying that I have it backwards on when the Telltale should be lit.

I am looking at the wiring diagram for a 5A which should be the same as a 5C (or 7 or 8 or 9) which shows a normal open contact on the brake current relay which gets voltage right off the brake light wire and sends it to the Telltale.

Something to keep in mind on a current relay is that it has to be adjusted for the desired current. If you change bulb number or change to LED lights, it will not work properly.

[belfert]

Is a telltale installed for the brakes so the driver knows if a brake light bulb goes out?  I've seen the brake telltale before, but my Dina doesn't have one and I wasn't sure why other buses have this.

It would have been nice to know that some of my brake lights were burned out a while back.  I didn't realize initially that my bus has four brake light bulbs plus the third brake light.  I still had brake lights so I assumed all was good, but only two of the four bulbs were working.  I don't even remember how I figured out there are four bulbs.

[Len Silva]

As I recall (maybe correctly) from an Eagle wiring diagram, the stop telltale is simply wired into the brake light circuit, no current relay.  Never understood the logic there.

Len

[HighTechRedneck]

As I recall (maybe correctly) from an Eagle wiring diagram, the stop telltale is simply wired into the brake light circuit, no current relay.  Never understood the logic there.

Len

If it's like my RTS, the parking brake activates the brake lights as well and hence the telltale lamp.  Hence it helps serve as an indicator that the parking brake is activated.

[Busted Knuckle]

BK: I don't understand your response. Do you agree with what I posted or are you saying that I have it backwards on when the Telltale should be lit.

I am looking at the wiring diagram for a 5A which should be the same as a 5C (or 7 or 8 or 9) which shows a normal open contact on the brake current relay which gets voltage right off the brake light wire and sends it to the Telltale.

Something to keep in mind on a current relay is that it has to be adjusted for the desired current. If you change bulb number or change to LED lights, it will not work properly.

Sorry Stan,
yes you are correct! & I added the part I accidently left out while in a hurry! (in my original post).   BK