Community Forums

cruzian · 07-03-2012, 11:16 AM

My ABS light came on while I was coming down a hill in stop and go traffic (stop sign at the bottom of the hill). I was going 2 to 3 mph at the time. We've all seen these light go on before and I have also seen them go on in buses that I've driven. A lot of time there is a sequence of things you can do to get the light to go off (I thought it would go off the next time I started the coach). Does anyone have any suggestions?

EngineerMike · 07-03-2012, 11:44 AM

Based on posts here, the usual culprit is an out of adjustment ABS sensor at one wheel. You can follow the sensor pigtail (its zip tied to the flex brake line feeding each wheel) to its conclusion in the wheel end. the sensor is supposed to push home to seat at a geven distance from the teeth in the brake disc that it reads to asses wheel rotation. Pull the sensor (may have a keeper you have to remove) & clean it, reinsert it so it seats fully.

Second most posted problem is melted sensor, brakes got so hot the sensor melted or partially melted. gotta replace that one.

Third most is the teeth in the brake disc have so much road junque in them that the sensor can't properly read the teeth. Cleaning is simple, use a brush, maybe some spray brake cleaner (I'd wear goggles for that as the splash back can be nasty if it gets in your eyes).

kraig · 07-03-2012, 10:27 PM

If you have a melted sensor and you have Bosch brakes, it should be a 3 foot cable, part #OW 4410328090.

Old Trucker · 07-04-2012, 04:01 PM

Quote:

Originally Posted by cruzian

My ABS light came on while I was coming down a hill in stop and go traffic (stop sign at the bottom of the hill). I was going 2 to 3 mph at the time. We've all seen these light go on before and I have also seen them go on in buses that I've driven. A lot of time there is a sequence of things you can do to get the light to go off (I thought it would go off the next time I started the coach). Does anyone have any suggestions?

Hi Cruzian, I am glad to hear you did not have TOTAL BRAKE FAILURE as I did in the mountains of SW Pa. My ABS light came on after some mountain grades, finally leveled out, rolled up to stop sign, NO BRAKES, pedal straight, to the floor with no resistance and would not pump up. Master cylinder was full. Everybody tells me that ABS could not cause this, but something did because it happend to me. I am a retired cross country trucker, I have owned trailers with ABS brakes and no problems. I finally replaced my master cylinder. Did that fix it??? good question. Before replacement it happened twice in 22,000 miles. Only time will tell now. Good wishes, Old trucker. PS Engineer Mike has always got good suggestions. Keep up the good work Mike.

cruzian · 07-04-2012, 05:48 PM

My point in asking is that a few years ago the Transit District i was working for received some new buses. Like most new buses they had a particular chronic issue. With these buses the ABS light kept coming on for some reason, but the mechanics couldn't figure it out. But what we did find out is we could get the ABS light to go out if you stopped the bus, turned if off and then back on. The ABS light would still be on, so then you would put it into drive and roll forward for a few feet lightly tapping on the brakes. The light would then go off.

I've heard of other vehicles having similar issues with ABS lights where a certain combination of turning the ignition on and off while tapping the brake would also get it to go off. I was just checking in the Alpine forum just to see if there was something particular to Alpines. Apparently there is not.

kraig · 07-05-2012, 12:24 AM

I had my 2000 for 10 years and only once did the ABS light come on. One of the brakes over heated and burned up the sensor. I think it would be best to look at Mike's suggestions.

Old Trucker · 07-05-2012, 02:24 PM

Quote:

Originally Posted by cruzian

My point in asking is that a few years ago the Transit District i was working for received some new buses. Like most new buses they had a particular chronic issue. With these buses the ABS light kept coming on for some reason, but the mechanics couldn't figure it out. But what we did find out is we could get the ABS light to go out if you stopped the bus, turned if off and then back on. The ABS light would still be on, so then you would put it into drive and roll forward for a few feet lightly tapping on the brakes. The light would then go off.

I've heard of other vehicles having similar issues with ABS lights where a certain combination of turning the ignition on and off while tapping the brake would also get it to go off. I was just checking in the Alpine forum just to see if there was something particular to Alpines. Apparently there is not.

Hello again CRUZIAN, On my 99 Alpine, when I set the parking brake, the red lights on the dash show Parking brake & ABS. As I had previously stated, I have had brake problems. I read some place that it is normal for the ABS light to stay light for a few hundred yards. Sometimes mine does that other times it goes ought imeadiatly after the parking brake is released. Maybe If I had idled for a minute or so may have some bearing. Maybe it is on a timer?? good wishes, old trucker

cruzian · 07-06-2012, 04:56 PM

After talking to a friend of mine who is an L.A. Metro bus mechanic he suggested first trying just tapping firmly on the wheel sensors with the back of a screwdriver. I tried this and got the light to go off as I drove away. A few miles later it came back on.

I pulled off the front panel nears the passengers feet (where the Vansco units are) and there next to the data port is a switch that is labelled "ABS Diagnostics". Now if I only had the software. But I did test the switch and did get a blinking code of 5 followed a number of 2's. My mechanic friend tells me that on Wabco systems the #2 means all is clear. I'll be taking the coach for a drive to see if the light goes off and stays off. And if not I'll retest. Interestingly enough, the code only showed up once. The Wabco manual says that stored codes will only show up once, so maybe I'm luck..then again maybe not. We'll see.

I did go into the ACA tech forum and found the manual for a 99-00 Meritor-Wabco ABS system. I am presuming that Meritor-Wabco is the system that is on my coach, although it may be a later version that 99-00. I went underneath to try and follow the wheel sensor to the ECU but it disappears behind a wall on all of the wheels.

Does anyone know whether Alpine always used Meritor_Wabco for its ABS system?

Here is the wheel sensor.....what is the best way to pull off the sensor to clean it w/o breaking it?