Saturday, September 29, 2012

Mechanic Troubleshooting Tales & A Blast From The Past.

When I was a 2nd year apprentice Mechanic in the late 70s I left the mining world and got a job up north at a busy truck shop, the oil patch was booming and Mechanic jobs were easy to find (even for rookies like me). The shop rate was $27/HR and I was pulling in $10/HR. If there was one mechanical problem I resisted (no pun intended)  the most it was electrical faults.

I'll never forget a White Western Star that came in and it had positive ground, you had to reverse your train of thought when it came to thinking through the circuitry. Anyways, back then series parallel switches were very common (12 volts running voltage and 24 volts cranking voltage). You just had to remember how the wiring went back together while the customer was standing there looking at his watch.

Through all that experience up to now and hundreds of shorts, no starts and charging system problems I've come to one conclusion.

Keep it simple and don't over-think the problem. If wiring continuity is disturbed with resistance, short or open circuit you're going to have trouble.  

SIDEBAR: If you ever have one or more circuits either not working or operating sporadically with relays or solenoids clicking on and off, there is a very good chance you have the blue stuff (corrosion) making a home in the connector or inside a module. It's happened to our equipment many times. The environment will take down anything that exposes itself!

If you look at an electrical system and think too broad you'll lose yourself. Think of the fault and the circuit, nothing else. A human friendly wiring diagram is most essential!

















Here is a perfect example of a wire that had rubbed through the insulation. Oxygen goes to work fast on this exposure. Luckily this problem was obvious to the human eye and not nestled inside a connector or module.  One other method we use is grab the wiring harness while the fault is active and shake the hell out of it. Sometimes this works to fish out a problem. A short might all of a sudden quit or an open circuit might reconnect while you're at a certain point at the harness or at a connection point.


As Mechanics we can learn and adapt as we go through our training and experiences. Get your hands dirty and you'll get more tuned into any kind of mechanical problem.

 Did you find this information useful?.....Please share this post.

6 comments :

Unknown said...

wiring is the most commonly avoided fault it seems , my co worker runs away when they come in .
this was today's C2 wire issue
loom between PDM & Engine , common fail point

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Piggingstring said...

John, your blogs have really helped me a lot in many ways. I have a 2000 International 4700 with a DT466E and it has a bunch of problems. I am NOT a mechanic by any stretch of the imagination, and right at the moment, their is water in the oil, so we are going to have the motor rebuilt just as soon as we are able to save up enough money.

Thanks for all the help you are to many of us "OLD" novices, and keep up the great work you are doing.

Rick
Rick's Towing

Palebushman said...

Hi John,
After nearly 2 years on our conversion project, we can pretty much say it is now complete, although in reality that will never be the case.
There is always something that needs attending to around the 'house' mobile or otherwise.

Here's our only problem at the moment, it is our noisy brakes, in particular the rear ones.
Although it is reassuring to hear and let other road users know I'm actually in the process of applying the brakes, I'm not so sure
that the noise should continue once I have removed my foot from the brake pedal. But it does go away after a few seconds.
My concern is how do I remove the drums in order to check for wear and tear. The inspection ports only show me that the linings have still
got considerable life left in them eg; a good half an inch on the lining thickness, and there is no sign of any 'wetness' to be seen either.
The bus is an Isuzu Austral Metroliner made in 1988 in Brisbane, and has a 6BD1-Turbo mounted at the rear. Brakes are air over hydraulics. Your help/advice would be much appreciated.
Best regards,
Dave.

Palebushman said...

Hi John,
After nearly 2 years on our conversion project, we can pretty much say it is now complete, although in reality that will never be the case.
There is always something that needs attending to around the 'house' mobile or otherwise.

Here's our only problem at the moment, it is our noisy brakes, in particular the rear ones.
Although it is reassuring to hear and let other road users know I'm actually in the process of applying the brakes, I'm not so sure
that the noise should continue once I have removed my foot from the brake pedal. But it does go away after a few seconds.
My concern is how do I remove the drums in order to check for wear and tear. The inspection ports only show me that the linings have still
got considerable life left in them eg; a good half an inch on the lining thickness, and there is no sign of any 'wetness' to be seen either.
The bus is an Isuzu Austral Metroliner made in 1988 in Brisbane, and has a 6BD1-Turbo mounted at the rear. Brakes are air over hydraulics. Your help/advice would be much appreciated.
Best regards,
Dave.

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