Community Forums

Dale Tomlinson · 07-19-2005, 07:11 AM

My ABS warning light came on and my speedometer quit working. I tapped the brakes several times and all came back to working normal. This happen several times. My parking brake had been sticking on lately (seems to happen after driving in rain). I don't know if this is related to ABS problem. Any ideas?

Dale Tomlinson · 07-19-2005, 07:11 AM

My ABS warning light came on and my speedometer quit working. I tapped the brakes several times and all came back to working normal. This happen several times. My parking brake had been sticking on lately (seems to happen after driving in rain). I don't know if this is related to ABS problem. Any ideas?

ISLAPP · 07-19-2005, 08:19 AM

Dale,
I cant help you with your question, but what I am gonna do is move this post to Motorhome General discussion since I presume it isnt Winnebago specific. You will get more answers on the general forum.
Mike

RV Wizard · 07-19-2005, 11:24 PM

You might want to check all your grounds. It sounds like one may be loose causing the ABS & speedo problem. Good luck & keep us posted.

Cruzer · 07-20-2005, 04:21 AM

If your parking brake is sticking in the On position (especially after rain) it has nothing to do with the electrical stuff. The rear brakes have two supply lines to them - service and emergency. When you release the park brake valve the diaphragm uses air pressure to overcome the spring tension that normally holds the parking brake on. If the mechanical mechanism is binding, it may not want to release. It could be a sticky slack adjuster pivot tube (when was the last time they were greased?) or rusty slack adjuster clevis pin. It could also be a sticky diaphragm in the brake chamber or even a sticky brake relay valve.

In 1999 Freightliner didn't use an MMDC controller so that's not a possibility but somewhere there is a valve that senses air pressure and triggers the brake lights/ABS, etc. It could be sticky or there could be loose wiring. It might be as simple as a loose connector plug on a wiring harness that lays under the dash and when you hit the brake pedal the harness moves - making and breaking a connection.

Those are some areas to look for but, either way, they are two seperate problems.

ottersea · 07-20-2005, 05:39 AM

I had a similar problem with the parking brake lite and it turned out to be a loose plug behind the dash going to the instrument warning lights. But in my case the light would not come on.

Hooligan · 07-25-2005, 06:27 PM

Antilock braking (ABS) and the speedometer on Ford and Chevy chassis use a Vehicle speed sensor (VSS). I dont know if Freightliner uses the VSS, but you might call them and see. The electrical signal from the VSS goes to both the ABS and the speedometer. The VSS is usually located on the tailshaft of the transmission.

chasfm11 · 08-02-2005, 02:58 AM

Dale, I've been fighting with an intermittent speedometer problem on my Freightliner XCS chassis since we bought our coach. We also have a problem where the low oil pressure light will come on and the engine will shut down occasionally during hard braking. I've worked with Allison and Freightliner Custom Chassis techs over the phone (in addition to spending $1,000 with a Freightliner Oasis dealer who didn't fix the problem) and here are some of the things that I've learned

1. According to Allison, if the speed pulses coming off the speed sensor are erratic, there are a variety of error conditions (i.e. shift inhibit)that will occur. I've had none of these. I've taken this to mean that my problem occurs after the output from transmission control computer.
2. According to the Freightliner wiring diagram for my chassis, the speedometer signals (along with several others) pass from the VDC (vehicle data computer)mounted in one of my rear compartments, through a harness over the transmission and up the driver's side to connectors mounted under the driver's seat. I've traced the cables from both the speedometer and the VDC and understand the routing and where all of the connectors are in this harness.
3. At the VDC, I discovered that the output connector cable was stretched very tightly and held that way by foam on the back side of the compartment. I wiggled the cable inside the foam and gained about 1/2" of slack. I opened the connector, which contains some very thin pins and sprayed it with DeOxit, an eletrical cleaner. With the newly created slack, I was able to reseat the connector and it now feels secure and centered in it's socket.

Prior to these last steps, the speedometer failed for about 80% of our last trip (needle rested at zero) and it has always failed at startup for about 5-10 minutes. After the opening and cleaning the VDC connector, I test drove the coach and the speedometer performed flawlessly. While this is a positive sign, I've had times in the past where it would work for most of a day without failing as well. We are planning our next trip on August 11 and will be closely watching the results. Even if the problem isn't fixed, I'm a lot closer to being able to isolate it than I was.

I hope this helps you.

Dale Tomlinson · 08-02-2005, 07:36 AM

It turns out, my problem was a faulty voltage regulator within my alternator. My Freightliner replaced with new alternator and all problems were solved. I also replace the 6 year old starting batteries at same time. They were going south. I have the Cummins Road Relay 4 engine computer terminal and it gave me the readouts indicating - overvoltage. My voltage was spiking to over 17 volts, causing the ABS light to come on and the erratic speedometer.