Auxiliary Engine brake activates brake lights

[jestal]

Who knew?

Long day through NC, Virginia, WV, Ohio on I-77 northbound. I hate vehicles and trucks that ride the brakes down long grades so I was busy with the engine brake to smoothly flow with traffic and remain stealthy. Driving into the night I discovered that any time the dash display shows "aux brake" the brake lights are on! So I was one of the cretins "riding my brakes" down all the grades despite my effort to not touch the service brake pedal.

I can somewhat understand the logic of doing this but it seems to create a nuisance and hazard for following traffic. How do they know when I suddenly really use the service brakes at an exit if the brake lights are already on (for long periods of time with the aux brake.)

Just an awareness issue if you overlooked the fine print.

[Cruzer]

That's been a long-running debate. On one hand, most RV owners use their Jake brake extensively, more than they should. If you are using it to slow down then the brake lights should be on. Whoever is behind you doesn't care what method you are using to slow down or stop. They just want to know when it's happening.

On the other hand, when you are just using the engine brake to hold your speed from increasing when descending a grade, it would be nice to not have those brake lights on so that they could be activated once you used the service brakes to actually slow down.

The problem is, the brake lights don't know which situation is currently active so the chassis manufacturers err on the side of safety and energize them whenever the engine brake is applied.

Until someone figures out they could read an actual decrease in speed via the engine's ECM and then apply the brakes this won't change.

[Tony Lee]

No different to going down a long hill riding the brakes slightly. A brake is a brake is a brake and the brake lights should be on when any form of braking is in use. (especially when some brag how effective their engine brakes are)

[Kuzzy]

I was two days from home on a 3 month trip when I realized my brake lights activate with my exhaust brake.
I would prefer they only come on with the service brake as that is when I am slowing down in stead of just holding speed.
A lot of new class 8 trucks come from the factory with the brake lights active when using the engine brake. You have to turn off this mode in the ECM.
On my Freightliner chassis I have to find a 1257 wire to cut to stop this.
To each their own but it drives me nuts to see brake lights on a lot. If you can't figure out the vehicle in front of you is slowing down you shouldn't be driving.


Dave

[hogdriver]

I don't care for the brake light illuminating when using the Jake brake either. As far as those following me I think it's the same as when I follow a big truck downshifting, I can't tell they are slowing except for my closure rate. I've heard it's possible to ask a Cummins shop to change the defaults on the Allison transmission and make the brake light come on only when the service brake is applied.

[Skip426]

Dave , I just e mailed you a diagram of my fix. Skip426

[Winepress]

I don't see the logic, but I understand why they wire them this way. If I downshift without the exhaust brake, slowing me down, should my brake lights come on?


Try and live up to your dogs opinion of you.

[jestal]

I would like to disable the brake lights with the engine brake since I only use it to maintain speed, not slow down. If the brake lights are on all the time with the engine brake then the lights are worse than useless, they are misleading to the driver following me thinking I am just riding the brakes to hold speed and then I suddenly use the service brake on top of the engine brake to make a rest area or exit ramp!

I was once admonished by a Spartan rep to use the aux brake for hills only and use the service brakes for "driving." The service brakes can glaze and rust if not used adequately and overuse of the aux brake can conceivably damage the service brakes from disuse. His point was that the coach has huge brakes so use them to keep them "tuned up." Use burnishes the drums/rotors, gets rid of rust and burns contaminants off the linings/pads. The aux brake in daily use defeats this logic so I rarely if ever use it except for long downhills where I don't want the brake lights on continuously.


Have to start looking at the wiring I gues for "that certain relay".....

[DeeGee]

I wish I could split the difference - the engine brake is two-stage, so what I'd like is for the lesser stage to leave the brake lights off, while for the heavier stage it's OK to have them on. Failing that option, I'd vote for having the service brakes be the only means of activating the lights.

[brobox]

I am one that doesn't worry about the exhaust brake turning on the brake lights. It's better than being tailgated down a hill. Drivers behind me normally don't want to follow a big blind spot MH in front of them. I would much rather have turn signals that let drivers know the big blind spot is changing lanes.

[Cruzer]

Originally Posted by jestal

I was once admonished by a Spartan rep to use the aux brake for hills only and use the service brakes for "driving." The service brakes can glaze and rust if not used adequately and overuse of the aux brake can conceivably damage the service brakes from disuse. His point was that the coach has huge brakes so use them to keep them "tuned up." Use burnishes the drums/rotors, gets rid of rust and burns contaminants off the linings/pads. The aux brake in daily use defeats this logic so I rarely if ever use it except for long downhills where I don't want the brake lights on continuously.

That is very true. Your service brakes are designed for 325,000 miles. You won't wear them out. The problem is when they start to get hot they release a layer of gas from the adhesives in the shoes or pads. The gas forms a boundary layer between the drum and if they are just "warm" (as far as brake temperatures go) the gas forms a glaze on the linings. If you use them hard you'll heat that gas and allow it to dissipate and your linings won't glaze. The best thing you can do is leave the engine brake off and use it for descent control on grades. I do leave it on when cruising down the interstate just in case I have to do a panic stop and need that extra braking power. However, if I'm heading to an off-ramp I reach over and switch it off.

Most service brake issues are caused by lack of use rather than overuse. A typical example is your ABS system. If you never use it the odds of it actually working when you eventually need it are pretty good that it won't work. Ideally you would purge the ABS valves before starting the coach. You do that by leaving the key off, holding the brake pedal down with decent pressure, then turning the key to the ON position without starting the engine. You will hear six pops in sequence as each ABS valve purges itself. Then shut the key off and continue to start the engine.

[PushedAround]

They should set up our coaches the way that they do the commercial Busses. Have a set of ambler lights that activate when using the compression (or exhaust) brake, and have the regular red lights for actual braking.

[hogdriver]

Originally Posted by PushedAround

They should set up our coaches the way that they do the commercial Busses. Have a set of ambler lights that activate when using the compression (or exhaust) brake, and have the regular red lights for actual braking.

That would make sense to me

[Kuzzy]

Originally Posted by Skip426

Dave , I just e mailed you a diagram of my fix. Skip426

Thanks Skip. I'll study it.


Dave