BCM Community
Bus Discussion => Bus Topics ( click here for quick start! ) => Topic started by: Mozz1k on November 05, 2020, 11:19:32 AM
-
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.
-
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. ;)
-
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.
-
The indicator light might be the engine door ajar - hth
-
Is it fully aired up when it happens?
-
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?
-
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
-
Thanks bus warrior!! I’ll see what I find out! I’m a rookie at this.
Best regards!
-
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.
-
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 !
-
BTW, brake lights will be on if Jake/retarded are switched on
-
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
-
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.
-
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.
-
Also, transmission brake "Jake" brake was off. So that excludes that.... This is a head scratcher :-\
-
If you don't have them already, you need the wiring diagrams for your bus. You could then follow the circuits connection by connection to find your problem.
Also, a transmission brake is a retarder. Jacobs are in the engine heads.
-
Are the wiring diagrams hard to find?
-
Have you tried to pull the fuse for the brake light circuit? If you have a short somewhere feeding the system, pulling the fuse on the circuit that is supposed to power them would let you know. If you pull the fuse and they go off, then they are not getting back fed from another circuit.
-
Call Prevost. They will get you the wiring diagrams, or any manuals. They will ask for you VIN.
-
If you farm out this work, be prepared to have your wallet emptied while someone else teaches themselves about your bus... if auto techs were any good at electricity, they would have become better paying electricians...
Better to suck it up and teach yourself, this is only the beginning of needing electrical investigative skills...
Not fun, either way...
Happy coaching!
Buswarrior
-
If you farm out this work, be prepared to have your wallet emptied while someone else teaches themselves about your bus... if auto techs were any good at electricity, they would have become better paying electricians...
Better to suck it up and teach yourself, this is only the beginning of needing electrical investigative skills...
Not fun, either way...
Happy coaching!
Buswarrior
LOL a little kernel of truth. It's not like you have to learn digital electronics. Just get on YouTube and watch basic electricity videos until it sinks in via osmosis. If you need an advanced degree buy a cattle prod WEG!!!
Ok I have had a few this evening!!!
-
Call Prevost with the serial numbers yours may have the chassis computer (CAN System) and the average person can do a lot of head scratching for days when all it needs is a re-boot
-
It is necessary to learn the basics but sometimes reinforcing what you read and learn and what happens when probing around the bus is so much harder. Can be deathly frustrating due to all the hands on wiring over the decades and screwing around with tapping with different color wire, rerouting wire around something not working, basic wires having internal breaks, etrc, x 1000.
Even with very solid understanding and experience, electrical gremlins can hurt the best of us.
-
BTW, brake lights will be on if Jake/retarded are switched on
Not on older units. There is a company manufacturing a kit to update your lighting system to make that happen tho. I guess if you are doing a bunch of mountain driving, it would be a good update.
joshenginebrakelight.ca (http://joshenginebrakelight.ca)
-
Ask yourself
I am jaking down the mountain, and 'round the bend, the traffic is stopped...
What does the rear of my coach look like to those following, when i have to go deep into the brake pedal?
If the brake lights are already illuminated for the last few miles...?
If you'd like to do something modern, add the amber lights up high that New Jersey transit has been using for decades now, and the Vanhool megabus double deckers too.
Solid amber when a retarder or jake is engaged, leaving the brake lights to indicate the brakes are being applied.
It's your bus, you don't have to compromise.
Happy coaching!
Buswarrior
-
But... If following vehicle doesn't know what those other lights mean.
-
It doesn't really matter if they don't know what the amber lights mean, the change in state is not nearly as accident triggering as the alternative?
About the only person on here that can dramatically slow their coach with the jakes is Cliff, with his ISX, just about all the rest of us, the retarder/jakes just drag, and don't represent the threat to following traffic.
Happy coaching!
Buswarrior
-
Isn't going to help idiots that don't allow proper following distance.
-
do it the easy way. An astute driver will keep an eye on traffic closing in from behind. If the situations dictates, then a couple short taps on the brake will inform the rear traffic to pay attention. I don't think it is wise at all and is misleading if the brake lights are triggered by the jakes.
-
I think this all depends on how strong the Jakes are. If they are like on a modern semi where they'll send you through the windshield, then perhaps the brake lights should be activated. However, if they're like mine where they just hold you at speed as you descend then having them on the entire time would mean that the driver behind you will never know when you use the service brakes with stab braking to drop your speed.