Dan Richter's response: (something changed and he couldn't post it himself... . ) Formatting errors are mine!
Fest3er
DOWG:Thanks for the kind words and sorry to hear about your problems with the brakes. Also, I appreciate you contacting us regarding the problems. I'm trying to monitor the site on a regular basis, but time only allows so much
surfing. First, the easy part. Outside pad wear is generally a slider problem whereas inside wear is a caliper piston. Sounds like the calipers hung up on
the sliders and you licked the problem. BTW, had the front axle been submerged at any point? Is doesn't take much dirt/rust to hang those things
up.
fest3er: Do you also only have 2 Wheel ABS? If so, you're the first one we're aware of that has had an EPRA problem with that system. We think that 3
EPRA's will solve the 4 WH ABS problem, and will be installing 3 of them on our truck this week. Abbott has said that they may be interested in making a
3 channel unit.
As far as the EPRA problem is concerned, in case anybody from DC monitors these forums, its incomprehensible to us that we have to resort to such chicanery in the first place when they know that a lot of people are going to install larger tires (especially with those huge wheelwells). DC should provide a way to make adjustments. Both Ford and GM allow their technicians and/or owners themselves access to the revs/mile in the ABS computer to compensate for larger rubber. DC used to allow this to a certain point, but the software for the DRB III scan tool gets updated nightly from DC and several technicians that we've spoken with said they used be able to adjust the revs, and knew exactly what we were talking about, but that feature is no longer there. The option simply disappeared off their menu screen. We shouldn't have to reinvent the wheel. No pun intended.
In reading the Dodge (99) shop manual, they give procedures for both manual and power bleeding of the brakes. For Rear ABS, it appears that no special tools are needed unless power bleeding the system, in which case the metering valve needs to be held open. There is a certain procedure that must be followed though. In the case of 4 WH. ABS, the DRB III scan tool needs to be used in conjunction with normal bleeding procedures. There is no adjustment procedures for the height sensing proportioning valve. I'm perplexed as to why the problem goes away with a load as that valve only increases line pressure and really shouldn't have any effect on the ABS system. Of course, the height sensing proportioning valve is increasing line pressure while the ABS solenoid is attempting to modulate the same line pressure. There may just
be some dynamics going on there that the symptoms go away, but the problem may still exist.
We've been working on brakes and speedometers this week so the thread comes at the right time. Unfortunately, I'm a mechanical engineer and other than the one electrical engineering class that we were forced to suffer through and my basic understanding of the subject, I'm no expert in the field of electronics. I don't have an answer yet, but I'm hoping that collectively we can get one so I'll just think out loud for now. DOWG didn't seem to have a problem until the brakes were worked on and fest3er has had the problem only since installing the EPRA. Only correcting the signal on one wire of the twisted pair has bothered me also. I'm going to get a hold of the engineer at Abbott and get their take on the subject as well as do some other research. We've also been thinking that correcting the signal between the CAB and the
PCM (pin 12, wht/orange) but need to know what we're trying to correct.
I'm wondering if any of the performance companies that deal with the electronics side of the 24V trucks (chips, boxes, etc. ) might also have some
insight into the problem. Anybody monitoring who wants to chime in, give us a call or e-mail. Its a business opportunity waiting to be solved and I'm not particularly excited about going into the electronics business.
fest3er, it sounds like you know about electronics. I'd be very interested in your results from monitoring the signal off the speed sensor. It's an AC (sinewave) signal that increases frequency as the exciter ring passes the sensor and the magnetic force is cut. Again, not sure the effect of modifying "half" the signal, but it does seem to work. Now, the signal coming off the CAB and going to the PCM, I'm assuming, is not an AC signal due to it being only one wire. I'm guessing that its either DC (Direct Current, not Daimler Chrysler) current or voltage that's being changed with vehicle speed. Our preliminary testing indicates it's a voltage change. If you have the know how
to monitor that also, maybe we can figure out how to change that signal and take the CAB out of the picture all together. I'm also going to try to get
some help from the electrical engineering dept. at my old school. The signal changes so fast with time that an oscilloscope or other digital data collection method such as the Postscript program that you mentioned is necessary.
Up to a certain point, the CAB only cares that all the tires are going the same speed (4 WH. ABS), or that the comparison algorithm does not indicate
imminent lockup (2 wh ABS) and does not necessarily care that the tires are going the "correct" speed. The problem with that method is that the CAB only
has so much tolerance in that comparison. Some Antilock controllers will allow as much as a 15% variation before tripping a code in the system while others may be as low as 3%. If the Dodge Controller is on the high end, correcting the DC signal may be the answer for both 2 and 4 wheel systems.
Any other electronics guru's who want to help, feel free.
Dan Richter
Rickson Truck Accessories
1-800-587-7633
PS: Would one of you post this on the Forum. Rob changed something and I can't post and the link on the homepage that would tell me what changed doesn't work. I have a username and password, but had never posted before.
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