Posted by NCWayne on August 13, 2012 at 22:53:22 from (69.40.232.132):
Troubleshooting anything on a machine can be a PITA, but electrical problems have to be the worst....especially when no diagram is readily available, and the customer needs the machine running ASAP.
Looked at a machine today for a customer that was having electrical issues that wouldn't allow the parking brake to release. They had taken it off the trailer at the job site and parked it and when they went back to move it a little later it wasn't right.
Based on what I could see and test I didn't have voltage at the parking brake switch, and that traced back to no voltage at the fuse block. Checked the posts on back of the ignition switch and had voltage there....but still none at the fuse block. No schematics to be found, but I was finally able to talk to another mechanic, at a rental yard, that had worked on more of these machines than I had. He told me a few other things to check that were on some machines and not on others. In other words, I was still 'on my own' in that he had never seen a diagram before either, and, like me, was just making a semi educated guess also. Anyway he said the fuse block is USUALLY fed directly off the switches ON post, but sometimes through a relay on the other end of the machine. So, I got back to the machine, check that there were no relays, etc, I missed previously, and then traced the wire as much as possible, again. Again I found no burned places, or anything else that would indicate why it wasn't carrying voltage from the switch post, where I had 12V, to the fuse block, where I didn't.
Finally decided to just pull the ignition switch out of the dash and 'bench check' it, even though it appeared good in the machine. When I went to disconnect the wires off the back the one feeding the fuse block didn't come off right. Instead of the whole spade terminal coming off, the wire and the crimped part of the terminal pulled out of the factory heat shrink insulating it, while the spade part of the terminal stayed on the switch.
Seems the terminal end was broken and the switch, which wasn't good and tight in the dash, had moved just enough when turned off to tighten up the wires and pull the two broken ends of the terminal apart. Being in heat shrink they probably would have never moved back together...and thankfully didn't or an intermittent problem would have been an even bigger PITA to find.
Things like this will drive you nuts. Voltage everywhere it's supposed to be, up until the problem point, and nothing apparent wrong until there. Had I not gotten to my wits end about 5 o'clock, and decided to pull the switch, even though it was checking good through it with the meter, there is no way I would have found the broken wire terminal hidden inside the insulating sleeve.
As many problems as somehing like a relatively 'simple' electrical problem like this, on a 14 year old machine without any electronics, really makes me think. I can't help but feel sorry for the poor guy, with the lastest and greatest piece of electronic machinery, when it comes to a screaching halt, in the middle of the field, with an 'electrical issue', at the worst possible time. Just think, 30, 40, or more, (or in this case only 14) years ago when a machine broke it was just a matter of tracing the dozen or so wires needed to make it operate to figure out what the problem was. Yes there was always the chance of something like a broken terminal, or something else odd and hard to find happening, but but basically it was all wires and switches, not circuit boards. Usually you could even bypass a problem to get the machine going until it could be properly repaired when it's work was done. Nowdays it has to be the factory part/computer, which is probably going to be a special order, nonreturnable (even if it turns out not to be the actual problem) item. Funny thing all of the electronic/computer technology that is supposed to provide so much cost savings for the owner winds up costing him almost as much, if not more, in parts, down time, and mechanics hourly charges when something goes wrong, than an older machine, that he could at least do a work around on himself, ever would.
Sorry, didn't mean for this to turn into an 'anti-technology' rant but days like today make me realize that as big of a PITA as any electrical problem can be, when you throw in the electronics it can be a true PITA and NIGHTMARE,to say the least...but equipment treads further and further into that whole nightmare with every new generation.......Funny the lastest issue of an engineering magazine I get has an article written by an engineer, who's son is also an engineer, basically saying that far too many machines nowdays are being over engineered with far to many features for the averageconsumer to ever figure out. Like he was saying, if his and his son's engineering degrees, and advanced education, weren't sufficient to help them figure out all of the technology in the average car, then things had to have gone way to far. So, for you guys with the latest and greatest, good luck..........
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