CD,
I can see that you are in a hateful situation.
While "Automation" has provided a great many benefits, it has also made it easier to make troubleshooting NOT easier.
The worst case being,
- You have a machine that runs under control of a program.
- You have no access to the program.
- There is no display.
- There is no manual.
The machine has been running fine for years. Now it doesn't.
The fact that the machine has been running reliably for so long indicates that the program is probably OK. It doesn't indicate anything about the quality of the program - only that it seems to work. Or at least, it did work.
Now, something has gone amiss...
Without knowing anything at all about how the program is written, you, as the local maint. guy, should have some understanding of how the process works. Or, you might need to rely on operator expertise.
At any rate, if any thing goes amiss on a system that has been working reliably for some length of time, you should feel pretty comfortable knowing that the problem is in the field - not the program. Now it becomes a case of knowing the process and checking the I/O related to the problem area.
None of us have access to the program in our car's computer (if any of you does have access, would you consider sharing?). But we know the general process and we can usually localize the problem.
This is not to say that any program that has been running for x-amount of time has proven itself to be good. All that has been proven is that the program has handled those situations that it has run into.
There is a whole bunch of "what-if's" that might, or might not, have been tested. The more complicated the system, the more difficult it is to test EVERY case. (It is possible to test for EVERY condition... but that can be very expensive in terms of time and labor.) So, only the more obvious cases are tested.
Many cases are dismissed as not being possible in terms of the process - yet, logically, they are possible.
How can two sensors, one at each end of travel, indicate that a "thing" is at-this-end AND at-that-end?
OEM: "This program has no problems."
USER: "How can you be sure?"
OEM: "No problems have shown up yet!"
The OEM is essentially challenging the USER to "PROVE the NEGATIVE". That is, Prove that the Program is NOT solid.
In this sense, every USER of an "Automated" system is a "Beta-Tester".
Once a program-fault occurs, the proof has been made! However, if a program fault does not occur, all that is proven is that you haven't run into the necessary conditions to cause the fault to become apparent.
"There ARE aliens!"
This is a case of "PROVING the POSITIVE". To prove this, all we need is to run into ONE alien.
"There are NO aliens!"
This is a case of "PROVING the NEGATIVE". To prove this, we would have to visit EVERY cubic-inch of ALL EXISTENCE (
is there anything beyond space as we sorta know it?),
AT THE SAME TIME! They could be avoiding us, don't you know?
JOE: "There are no aliens."
JACK: "How can you be sure?"
JOE: "No aliens have shown up yet!"
RESET TANGENT:
One of the more painful aspects of being a USER is that you are subject to what the Program/System will let you see or do.
In some systems, as long as things are fine, then things are fine. But when something goes wrong...
JOE: "What's wrong?"
JACK: "It's broke."
JOE: "How do you know it's broke?"
JACK: "It doesn't work."
JOE: "Is it plugged in?"
JACK: "Yes."
JOE: "Is it turned ON?"
JACK: "Yes."
JOE: "Was the START Button pushed?"
JACK: "Yes."
JOE: "What happened?"
JACK: "Nothing."
JOE: "Should something happen?"
JACK: "I don't know."
Joe: "So... What's wrong?"
JACK: "It's broke."
This is the "unspoken" intercourse between Man(Joe) & Machine(Jack) in a system that is designed under the assumption that, as long as all is well, Jack (the Machine) will behave as expected.
If the program is not designed, from the beginning, assuming that shizt happens, then that program is saying..., "If I'm broke, I dare you to find out why!"
And so, you sit there, staring at a black-box, wondering what to do. If you don't have the documentation to help you solve this problem, or if the system has not been designed to help you, via self-diagnostics of some kind, then your only option is to call Tech-Support.