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Brake light/buzzer problems on 2003 Lexa

Yahoo Message Number: 69656
I'd love some advice on diagnosing a problem that's driving me crazy. Literally.
My park brake light is on continuously, EXCEPT when the park brake is actually on! And the buzzer is on continuously. Talk about getting a headache. And the wife isn't happy either. And when momma ain't happy, ain't nobody happy....
Not only is buzzer and park brake light on, but the speedo is fixed at 24mph (luckily my GPS shows me actual speed), and the Jake brakes work fine, but don't turn on the brake lights when they engage (like they did before this happened).
With some weather, I was in a line of trucks, all doing ~20mph up a hill. I put my flashers on. Of course I'm getting a buzzer every time they blink. After a couple of minutes, the buzzing went steady. I looked and saw the park brake light on.
I did some testing of brakes, rolling resistance etc. and all seemed fine. When I was able to pull over at an exit to check things, all seemed fine - no hot wheels, no brake lining smell, no grabbing or dragging while rolling slowly, etc. Rechecked again when I got to somewhere I could spend the night (Redding CA). When I pulled over to first check, I opened the owner's manual, it said that park brake light is on when park brake engaged (this has actually never worked, since I recently got the coach, this is in fact the first time I ever saw the park brake light), but this clearly isn't the case. No other help in the manual on diagnostics etc.
Parking brake engages and disengages normally. Other than light, buzzer, speedo at 24mph, and no brake lights when Jake Brake engages, no other apparent symptoms. If I have to make a wild guess, I'd think perhaps an ABS wheel speed sensor issue, that perhaps thinks one of the wheels is stopped?
I did get a recommendation from the RV park for All Wheel Alignment & Brake in Redding, which according to their card does 'Complete Auto, Truck, and RV Repair', so if I don't have any better ideas in the next hour or two, I'll stop by.

Jim Walsh
2003 Lexa

Re: Brake light/buzzer problems on 2003 Lexa

Reply #1 –
Yahoo Message Number: 69657
Sounds like a loose or bad ground. Sounds like a lot of cross feeding due to a ground issue.

Mikee

Re: Brake light/buzzer problems on 2003 Lexa

Reply #2 –
Yahoo Message Number: 69659
First guess- faulty ground
They can be HELL to find.
Jw

06 inspire 51544

Re: Brake light/buzzer problems on 2003 Lexa

Reply #3 –
Yahoo Message Number: 69663
Thanks Mike, found a shop in Redding with a good electrical guy. It's blowing a 7.5 amp fuse that runs much of the dash.
Seems to be when I have four-way flashers on and the Jake Brake comes on, or vice versa. If I stay away from the flashers everything seemed to be working fine.
Happened on test run after replacing the fuse, slowing down on a freeway exit, hit the flashers and immediately blew the fuse. Can't replicate sitting here with the brake pedal, so I'm guessing it's Jake but I might be wrong, definitely something relating to brakes and flashers at the same time.
Not sure if it's related, but changing some wiring now for the brake controller I recently had added. Changing brake +12v input wire to controller, per Bob Vinson at OMCC, from currently a wire that's going to the SmartDash, to a rear brake light wire, run forward using one of the dash spares.
Found the spares in the back (just above chassis batteries) and the terminal strip in the electrical bay, can't find them under the dash itself, so just running a short wire from the bay to the dash.
If this doesn't resolve, I'll just keep a bunch of 7.5 amp fuses, and have my wife smack me whenever I turn on the flashers without turning off the jake brake first, until I can get it fully sorted out.

Jim

Re: Brake light/buzzer problems on 2003 Lexa

Reply #4 –
Yahoo Message Number: 69669
Change it to a 10 amp fuse, the problem should go away. 10 amp fuse will not be too big to protect the circuit. Sounds like the 7.5 is too small for the items on the fuse.

Mikee

Re: Brake light/buzzer problems on 2003 Lexa

Reply #5 –
Yahoo Message Number: 69672
Found the problem and how to repro it 100%, but don't know the root cause, or how to fix it.
Looks like it's a Coach-specific problem, nothing to do with trailer wiring, as it repros with brake controller and all associated wiring fully disconnected.
It's definitely whenever the four-way flashers are on, and the jake brake engages. Blows the 7.5 amp fuse every time. Doesn't happen at all with coach brakes, so it's not as simple as a brake light circuit problem.
Yesterday was likely the first time since I got the coach where hazards and jake brake were engaged at the same time, as it's the first time I turned on the hazards while driving, and it's hard not to engage the jake, as any full throttle lift will start engine braking.
The fuse that's blowing apparently has nothing to do with any of this, no jake brake, no hazards, no turn or brake signals, no anything that seems related. The fuse is controlling wire #'s 76 (16 gauge blue) and #77 (16 gauge yellow), controlling 'Front Run Board, Air Purge Relay, Dash Alarm, DRL Module'.
Done for the weekend, the shop is happy to start up again on Monday, but I'm not sure they'd be able to do much other than continue trying things until they stumble upon something.
Any suggestions on where/how to get this flaky problem diagnosed? I'm a little leery to head an hour back in the wrong direction, and wait around part of a weekend, to have a specific shop continue working on it. Only plus is that they know exactly what they have and haven't looked at so far, but most of that was diagnosing exactly what was happening, and a bunch of work that suspected the brake controller or associated wiring.
Trailing being connected makes no difference, exact same behavior either way.

This is a strange one.
Jim

Re: Brake light/buzzer problems on 2003 Lexa

Reply #6 –
Yahoo Message Number: 69679
Hey Jim, I've had a number of electrical problems with my coach. After the first one.... which cost me hundreds..... I stopped looking for the problem and simply asked the shop to rewire the infected(?) device. This solution has saved me untold grief and money. It's quick and sure. I've done this with a problem in the tow loom, another in the smartwheel loom, another in my awning covers. So far, knocking on wood, it's always solved the problem. The alternative can/will result in hour upon hour of "searching!"

Mel Shapiro
LEXA 6177

Re: Brake light/buzzer problems on 2003 Lexa

Reply #7 –
Yahoo Message Number: 69690

Jim the park brake gets a ground signal, if this is not happening you will get the symptems you are describing. In the service bay below the drivers seat there are 3 white plastic air switches, one of these is the park brake switch. It might be bad or have lost the ground. P.S. i have most of the paperwork on all of the Lexas and have had the pleasure of working on every one of them at CC when they were built. If I can be of assistance give me a call at 1-541-556-4784

Re: Brake light/buzzer problems on 2003 Lexa

Reply #8 –
Yahoo Message Number: 69800
Thanks Mike, that did it. No problems w/ 10 amp fuse. Either 7.5 was always too small, or resistance in some operated circuits on that fuse (dash flasher lights, tach, speedo, oil & voltage gauges, etc.) has increased enough over time, that 7.5 no longer cuts it.

Jim

Change it to a 10 amp fuse, the problem should go away. 10 amp fuse will not be too big to protect the circuit. Sounds like the 7.5 is too small for the items on the fuse.

Mikee