Brake lights stay on

[Mozz1k]

I recently bought a 2000 Prevost H3-45 to convert into a motor coach.  Everything is great with it, but the brake lights stay on, and there’s an indicator light on that looks like the back of the bus. Does this have something to do with the parking brake? Need help. Ha.

[Van]

Chock the wheels, Transmission in Neutral, start bus and release the Parking brake. Brake light still on? it should go out. There is a relay (probably in rear elec panel) to eliminate the  brake light when parking brake is engaged. Light on dash is normal when ever service brakes are applied.

[Mozz1k]

Okay! I’ll check for a relay. Yeah they stay on whenever the bus is running... parking brake on or off it doesn’t matter either way the brake lights stay on. I looked for anything in the way of the brake pedal, and pulled up on it.... still lights stay on.

[niles500]

The indicator light might be the engine door ajar - hth

[Dave5Cs]

Is it fully aired up when it happens?

[Mozz1k]

Whether it's fully air'd up or not.  Tried pulling cycling the yellow air switch, also pulling up on the brake pedal.  Checked the rear compartment.  It is latched.  I'm wondering if it has to do with a switch under the yellow parking brake handle?  Wonder if there is a switch in there that indicates that the parking Brake is on?

[buswarrior]

Brake lights are applied by a number of pressure switches, both ones that come on with pressure, and ones that come on in the absence of pressure, depending on whether they are plumbed into service or parking systems.

One of them has shorted, or is being shorted across?

Your multi-meter, the schematic, and a hunt for them all to test...

Happy coaching!
Buswarrior

[Mozz1k]

Thanks bus warrior!! I’ll see what I find out! I’m a rookie at this.

Best regards!

[chessie4905]

Check for sensors with one or two wires coming off the brake application valve. ( brake pedal). Underneath in under driver compartment. You should see several air lines connected to it and one or more sensors with wires. You can disconnect one of the wires and see if light goes off. Unfortunately on newer models, they frequently use that switch to activate a relay to energize the lamps, so could still be bad relay and switch is ok.

[Mozz1k]

Ahh good to know!! I will deep dive into this this coming weekend! I will update and probably ask more questions as I go. Thank you !

[niles500]

BTW,  brake lights will be on if Jake/retarded are switched on

[Mozz1k]

Oh I had no idea about the Jake/retarder. I’ll make sure that’s off. I’m pretty sure that has been off. But I’ll double check

[HB of CJ]

Does the coach have a Jake?  Did it once have a Jake?  I think nowadays when the Jake is working the brake lites come on?  Is this true?  My Crown had a dash indicator light that came on when the Jake was operating but the brake lites did not come on.  Long ago, far away.  Could some relay be bad or just deleted?

Yeah with the idea of making sure the brakes are not dragging, even when not applied, setting off the brake on light.  Good luck.  I love figuring out this kind of stuff ... others hate it.  Oh well.

[Mozz1k]

So, I unhooked one of the wires that goes to the Yellow emergency brake handle.  Lights still stay on.  I contacted the place where I bought the bus.  They suggested a couple of things that were mentioned previously.  Lastly they said it is a short probably buried in the wiring.... and wished me luck.  Ha! Sooo I might bring it to a diesel & pickup specialist and see what they suggest.

[Mozz1k]

Also, transmission brake "Jake" brake was off.  So that excludes that.... This is a head scratcher