New Allison 10 speed

[Oonrahnjay]

  (snip)  I have had cars with apparently unsolvable electronic problems.  I have known people that got rid of cars after the frustration of trying, even when using theoretically qualified mechanics.   

     Lin, I tell people that I grew up datin' North Carolina girls, I worked for British companies for 20 years, and I used to be engaged to a redhead -- so I KNOW what frustration is.  But I've never been as frustrated as trying to find an "intermittent" electrical problem!  I can't imagine everything being run by a little computer.

[prevosman]

Lin,

I am not a professional. I always worked on my vehicles, but with rare exception my efforts were related to oil changes, lube jobs, changing plugs and points, etc.

When I go my first bus in 1990 I did nothing to it other than drive it to Prevost for service. But when they decided they did not want customers in the shop (a policy now reversed) I decided if they can do it, I can do it. Since then there is not much I haven't done. In the course of 20 plus years I have not only done a whole lot of work on both the house and chassis, I have learned the bus, its systems and the system logic. Self taught, mostly by hands on experience in concert with the hop manual sitting in my lap.

But I was always a little intimidated by the electrical side. I could bumble my way through a problem, but when the multiplex cam out I was convinced ponly trained technicians with computers and special software could even think about working on an electrical problem. But Prevost offered factory training and I signed up. A private owner somehow slipped between the cracks and I got to share a class with real mechanics.

But as the training session unfolded and we were taught theory and principles of operation, mixed with accessing and interpreting wiring diagrams, all combined with hands on training on real buses with real problems. The hardest part turns out is developing the discipline required to not shoot from the hip, but to take the information the message center is providing, and tying that in with what the wiring diagrams are showing. Often trouble shooting was nothing more than isolating the message center errors to a single specific part common to all the listed errors. None of the trouble shooting could be done without reference to the diagrams.

At the end of the session we all were very comfortable knowing what we could do and not, and more importantly how to use the message center like we would a driver trying to describe a problem. The message center gives us all the errors, and then we just have to look on the wiring diagrams to find what circuit or component was common to the listed errors and without even working usp a sweat we could go right to a defective relay for example, replace it with a good one and see the message center no longer showed errors. But if you are not disposed towards doing the diagnosis of problems methodically with a study of the bus systems via the diagrams you are in trouble, probably as much trouble as you would be in if the coach was not a multiplex coach.

As much as I used to fight that kind of progress I now actually realize it is far better than what we had before. I am speaking only of Prevost here and it might not apply to any other coach or vehicle.

[prevosman]

  (snip)  I have had cars with apparently unsolvable electronic problems.  I have known people that got rid of cars after the frustration of trying, even when using theoretically qualified mechanics.   

     Lin, I tell people that I grew up datin' North Carolina girls, I worked for British companies for 20 years, and I used to be engaged to a redhead -- so I KNOW what frustration is.  But I've never been as frustrated as trying to find an "intermittent" electrical problem!  I can't imagine everything being run by a little computer.

But that is the point. The system itself points you in the right area for trouble shooting. Usually a problem that is occasional goes away by the time you start to grab your tools to start looking for it. But in this case you can either see the error message or access the memory. Depending on what system malfunctions are identified you can isolate a specific component or system portion that has the malfinction. If one of the modules is acting up, or you think it is acting up, swap it with another one. If the switch relocates a problem it is easy to focus on a bad module, but if the problem stays where it was, then the problem lies with the coach.