mis-diagnosed a problem



mis-diagnosed a problem

Postby grumpyvette » December 26th, 2011, 11:32 am

we have all done it, or had someone working on our cars do it!, and probably will continue to do so, the shop manual, the person doing the work on the cars experience or a few test results point to a defective part, resulting in you or the shop you bring the car to mis-diagnosed a problem , this can get very costly and time consuming and its a total pain in the A$$ but theres not much that can be done in most cases because you can not usually return used parts, once they are installed ,and in many cases you took the car to be worked on because you yourself didn,t know how to test and replace the parts or it took tools you don,t have access to to do the work, and in the case of electrical parts it occasionally results in the new part burning out , so obviously the more testing you do and the more you isolate each part of any process to narrow the potential choices of defective components the better off you'll be.
example my computer trouble codes and shop manual say that a relay is defective , replacing the relay has zero effect on the problem, it eventually turns out to be a combination of a bad ground, corroded electrical connection and two defective sensors, the total cost and time far exceed what might have been required if you knew before starting what the exact cause was.
INTERMITTENT PROBLEMS ARE THE WORST, FOR THIS BECAUSE YOU MIGHT FINE THE PROBLEM (CURED) for a few days after works been done , but then it comes back, and you start over from scratch, bad fuses, stuck relays, bad electrical grounds, loose electrical connections, loose connector clips, leaking vacuum hoses and corrosion can make you nuts
dealerships hide these mis--diagnosed, and extra extra parts being installed as standard practice , they just bill the parts and time as required and assure you only the defective parts that needed replacing were worked on, but at times its rather obvious that the (MECHANICS) are clueless parts swappers who just replace parts the trouble codes, or random guess work, indicate, then fail to test carefully, and have zero idea as to what effects what or how things really work,
well? whats your stories

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IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: mis-diagnosed a problem

Postby mathd » December 26th, 2011, 1:33 pm

We had 2 electric problem(one was intermittent) in the pontiac Grand Prix GT 1998.

The first was when using the heater/blower fan on the 1 to 4 setting(5 worked fine) we lost the daytime running light/defrost and lost power on the most part of the car's circuit but the car could still "run".
The Factory called for the blower resistor(wich i changed the previous years and after some test was not defective)

Went out to a few local mechanic AND OEM dealership for a quote. none could answer a price because they had to "find" the problemS(they seemed reluctant when asked to find 2 electrical problems)....
The dealership is at 100$ an hour, that can get expensive really quick.

So i taken the car electrical wiring diagram, my multimeter and a few screw driver.. After no more that 1 hour of testing i found both the problem.

The first problem was: one "side" of the ignition switch that lost contact when under high current load.
The dealership and local parts store asked 280$ for the ignition switch...parts only no labor :/
I bought a bosch 30A relay for 8$ and after no more that 30 min it was fixed and working perfectly.

The other problem was intermitent complete lost of power(engine die, no hazard, no horn no power at all.)
This one was simply a bad chassis ground.
That was obviously an easy fix.

Now both problem where fixed for no more that 40$ :/.
Mathieu
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