Can't get over how many people including big bosses and managers don't understand simple testing. You tell them that the brand new battery has zero capacity according to your not 1 but 2 Fluke 87-5 multimeters and they will tell you your meter is no good. You try to explain that a simple boost and the unit fires right up proving your meters diagnostics as the ( New ) battery dropped to 6 volts in the 2 seconds of testing recorded and stored on the 2 meters. They will argue tooth and nail that a new battery can't be faulty. I try to tell them that I seen 4 batteries that were all bad even after trickle charging for 2 days. Junk is just junk some times. Argued tooth and nail with a shop foremen that the brand new machine that had no power at all to dash had an internal disconnect at the battery connection itself. The meter leads touching the dead center of the positive post and 1 inch over into the red positive cable, pushed in to be able to see copper was recording 11 volts on the meter with someone turning the key to start. He suggested pulling the starter. Both test leads one inch apart on the same power source should never give any kind of sizeable voltage drop, never mind 11 Volts. It was liking talking to the wall. So I cut the cable off. Put a new heat shrink piece on the cable and crimped on a brand new positive end. Then heated the heat shrink to make it look pretty. Wow what brilliance. Everything fired right up. They dont know how to test a bad ground or positive cable and don't want to know either. They don't know how to test if there is a loss of power to the computer positive terminal or to a fuse panel. It sure does make me giggle and wonder how they got their job. Have you ever met that kind of brilliance. Simon C
Usually referred to as bell-ends.......
I was about a month in at a new job. The shop lead asked me to try and see if I could get a newer D4 running that wouldn't crank and had been stuck in the wash bay a couple days. A few guys had taken a stab at it. They attempted boosting, new batteries, new starter, disconnect switch etc. Within about 15 minutes I had it running. The big lead post clamp that CAT uses on the battery cables when they connect 2 cables together to put the batteries in series must've not been built correctly. First thing I did was obviously try and start it, thinking maybe someone left the gear selector in gear or park brake switch off. No dice. Looked at the batteries, negative on the first battery looked like it was smoking slightly, it was hot to touch. Put meter on post and then on ground stud and cranked it. Had over 11 volt drop. Connected a pair of jumper leads from the faulty negative clamp to the frame. Fired right up.
Once you find a huge voltage drop a simple booster cable can confirm the problem as 92U 3406 said. Then a person can decide the easiest fix. So many do not know simple tests. As 92U said, ( They change everything imaginable without proper diagnostics ). Glad you have your oars in the water. Simon C
I'm definitely not the best troubleshooter out there but I try my best to not just throw parts at things. Its a matter of pride, I want to know 100% that the part I'm saying has failed has actually failed. If an extra hour of diagnostic time rules out a thousand dollar starter, we're still $800 ahead of the game.
First things I alway check are the batteries and the leads off of them. It's just always the easiest and most inexpensive place to start. For some reason people just jump to conclusions about electronics and crappy systems when the most common problems are the basics of any electrical system.
There are so many things you can do with properly sized resistors and capacitors and choke coils and diodes, I understand these things but do it so infrequently that each time is a re- education LOL. Troubleshooting electrical requires some quiet time for me, while I line up Occam's Razor on the problem and find the shortest path to the first steps.
Had a newer Kenworth come to the shop with a starting problem. The company that owned it had their mechanics look at it and they could not find the problem. It had zero voltage to the starter and alternator. They were boosting it to be able to use it. The battery disconnect switch on the battery box in the cab was in the off position.
I had this just the other day. Phone call from a new vendor, we have had a work order on this 3 weeks, nobody will come look at it. Unit won't start. I go up there and start poking around. Everything is dead. Find the e-stop mushroom pushed in, pull it out, still dead. Meter the switch, no voltage. Starter and alternator, no voltage. Battery has voltage. Poke around, found battery switch hidden and off. Turned on. Unit starts normally. I suspect whoever operates it knows about the batt switch but the red mushroom switch is hard to see what position it is in, and if turned off will probably just give strange hieroglyphics on the display.
Correct me if I'm wrong John-Years ago long before the millennium long before the PC, ECM, or electronic ignition--was point type ignition. In those days it was common/standard practice when performing a tune-up the battery and connections were cleaned first. But when fuel injection and breakerless ignition came along that stopped. Just like checking the oil at gas stations, the mini mart put a end to that. Hell people don't even wash the windshield they wait for rain.
I make a good living on poor maintenance programs parts changers and guys with jumper wires
Its scary how many folks wrench for a living that have no business putting air in their pedal bike tires. Some of the stuff I seen Journeymen do back when I apprenticed was mind blowing. Rigging up a brand new $800k machine and they just hack up the wiring behind the seat. No joke one guy wired up a bunch of accessories by bolting together a bunch of ring terminals and wrapping with electrical tape. I'd honestly beg to see Scotchlocks on there over that (and I've thrown away every bag of those things I come across).
Couple years ago I had a truck at one facility that was a "no start". One of my guys claimed to be an ace mechanic so I sent him to diagnose the truck. Gave him a voltmeter and specific instructions to test the voltage at the battery and again at the starter. He came back and told me the truck needs a new starter. I went and retrieved the truck with an equipment trailer and brought it back to the shop. I started my own diagnosis and noticed there was no chime when I opened the door. Tried the headlights and nothing. Put the voltmeter on the battery and it was stone dead. I hooked the battery charger to it and noticed the interior dome light came on. The truck had been parked for the weekend with the light on!! After about 20 minutes charging the truck started right and ran fine thereafter. Between this incident and several others exposing his lack of knowledge he's no longer a member of my crew.
Other day machine comes in with codes for aftertreatment issues. They put one of our guys who just graduated from our apprenticeship program this year. I have instructed him previously that the first thing you do when T/S is to check that each fuse is getting power across the terminals with the voltmeter. he told me he “checked them” and then I guide him through more tests and troubleshooting but all wiring tests good. I think we all know where this story is going… day later he finally comes to me in frustration and I tell him start over and make sure he missed nothing while I finish up another project finally get back and he says “well it makes no sense I don’t have voltage here where I’m supposed to to this engine ECM” it was the fuse. He didn’t check key on, voltage across the back test points like I had previously told him to do. Blown fuse was the ONLY issue. It’s not a lesson he will ever forget at least.
The other-if you suspect a bad relay, test with a new one, don't swap old tired relays. The other if headlamps don't come on, check both headlamps first before jumping to conclusions.
A couple of stories, mid 1980's guy had a brand new Ford pickup that just died going around a corner. Had it towed to the gas station I was working at and the owner spent the better part of a week working on it. Only had one spark from the coil when you turned the ignition off. He had checked "everything" had followed the diagnostic chart and replaced numerous items with no success. Finally one day he had me crank it over for him and I noticed there were no dash warning lights with the ignition on. Turns out the 5 amp dash warning lights fuse was blown. Ford has told him that there was no fuse in the ECM system but apparently the ECM did get a signal from the dash lights. Then there was a local trucking company that had bought 3 new Mack dump trucks which they ran 3 shifts a day. One of the three would just "up and die at any time" while driving. They had their mechanics spend time on it with no success, so they called a local guy who was very good at diagnosing electrical problems. That's when it came out that it only happened to one driver so they went for a ride. This driver shifted very hard and that's when the truck would die. Pull over and it would start right back up. They found a poorly crimped ground cable that was also too short so every time the guy shifted and the engine rocked it would lose contact. Never overlook the obvious but it's often something unusual, which is why it can be so interesting and rewarding.
The sad part is the factory manuals don't have very good trouble shooting. They tell you to ohm a wire to verify its good. It should only be tested with a load as a wire almost broke in to will show good continuity. I know guys make fun of you tube but there are serval guys there that know there ****. Scanner danner and south main auto are just a few. From what i see is the auto guys are way ahead of the heavy equipment guys in testing. I recently got a scope and its amazing what you can do with it.
Yep, used to work in a repair shop, before attempting any electrical diagnosis, clean all the terminals and charge the batteries all the way, then test the batteries and then go hunting, usually the problem was gone.
I hate those, if I do it that way, I don't know if that fixed it, or if it is coming back at the next inopportune moment.
Have you tried compression testing with and inductive pick up on the starter wire yet its an amazing job for a scope wish I had learned more on scopes before I left automotive world Electrical is hard to teach just like showing someone how to grade by butt feel
Very true. I'm glad the trade schools I took my apprenticeship training at had electrical, hydraulic and air brake boards that a mock up system could be built and troubleshot. Sometimes we'd even get vehicles or machines in with problems that they'd turn us loose on to try and figure out. Beats reading a text book. Theory is important but if you can't translate that to the real world then you'll have a hard time being effective on the job.
The apprenticeship is the time to learn. Once you get those Journeyman papers you're thrown to the wolves - no mercy. Had one apprentice I mentored for a bit. Guy was afraid to step out of his comfort zone of oil changes and stickers. Even with me volunteering to work alongside him on some more difficult tasks he didn't want to do it. Last I heard he never managed to finish the program.
This all sounds like easy money to me!
Vehicle has electrical issues, never fails the person behind the wheel--How long will this take? To get the proper reaction for asking that question--At least 18 hrs, but I have doctors appointment in 1.5 hours, will be gone the rest of the day and may not be able to work tomorrow.
Always been the cream that floats out for those that know how to collect it!! Battery cables can appear Brand New and be worthless, odd crack or as in some Fords, a Frame Ground mid cable lets all the nasty in and the cable commences to break the line, still looking New. Clean the cables on my old F250 SD at least twice a year as seemingly sits forever. Batteries this last time went seven years. Glow Plug relay just like a ford start relay and just as contrary, usually one every two to three years, last one failed was four years old, tested for output voltage on a test light, NADA, quick easy fix for long colder crank. Although the Magic Smoke Gremlins CAN BE Gremlins and do some seriously Odd **** on occasion.
Part of Freightliners 100 plus recalls for Cascadia's-the positive 4 post battery bridge. Everyone of ours had to be replaced.
I keep a cheap little compass in my electrical test box. Ever wonder which way the power is traveling in wire? Place a compass over the wire and whichever way points north is the way the electricity is traveling. It also be used to find electrical shorts.
And first thing at 5:45 am today. Trailer for service and I notice it has a dim top right marker at rear of trailer. Load my tools on the Genie and up I go. Now so people understand this marker on this certain brand of trailer also flashes with signal. I had already seen a repair order from another shop charging roughly $130 labor plus parts three weeks prior. Remove the rivets for cover plate and a brand new Super Nova was installed, problem was it wasn't the problem. The harness in this trailer was made by Truck Light on bid for Van Guard Trailers. This particular marker is a Dual Intensity Super Nova, built with resistor inside harness so it interrupts constant marker power with a right hand signal power. Well it was pretty obvious who ever worked on it thought it was a bad light with poor grounding. So they just cut the old one off and spliced in a new marker-that didn't fix it so just fack it and run it out the door. Below is the culprit the resistor built inline and the whole thing hardwired as a unit with light. I cut it apart to show the orange/brown corrosion collected on white/ground and shrink tube cover. Obvious they didn't check for ground first but they did check for power by poking a test probe into marker wire. The thing is this light is not a DOT mandatory signal light so the fix is remove the whole piece, forget the signal wire and turn it back to a 2 wire marker. This pos is roughly $25 bucks a piece. But this is one of those where who worked on it had no clue.
Amen brother! I have said this before, When it comes to repairs, or troubleshooting, I'd rather get yelled at for taking too long than for doing it twice. I do too. Awesome little tool.
Yes i have used the relative compression test. Just used it on the girl friends car to find a dead hole. Serval of the scan tools have it built in. I also have a pulse sensor that you can put in cooling system to see if you have compression getting into the system. You can also put a Triger on it and find what cylinder it is. Im working on finding a sensor that i can pick up slight flow of hydraulic oil to find leaking valves with out opening up the system.
Hear is a great kit for trouble shooting. https://www.aeswave.com/uTest-Advanced-Terminal-Test-Kit-p9748.html
Reviving an older post but this reminded me of the parts changer a previous manager was always praising for his completion times. Sure he could guess accuratly a lot of the times but when that didn't fix it, the job turned into a disaster. Shop foreman didn't believe my diagnoses that the product link computer was bad and draining the battery. So the foreman had this parts changer come over to go over it again, but the "tech" has no idea what to do with a hybrid loader and all the weird readings he was getting. He tore that loader's electrical to pieces. Luckily I was reassigned to another job so I didn't have to clean it up. Ended up being the computer, guy told me he just guessed at it was the last thing he could think of.
Thankyou for that!
yes have, If you can Triger off an injector will lead you to the exact cylinder.