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Ann R. Thryft
User Rank
Blogger
Re: Group knowledge
Ann R. Thryft   10/29/2012 6:00:23 PM
NO RATINGS
This story reminds me of our current problem with my husband's aged Honda coupe. The check engine light has started to go on occasionally, usually solid but sometimes blinking. Then it goes off, for days or even weeks at a time, before going on again. After reading what seems like a zillion forum postings on this issue, we've decided that the alternatives are many: sensor malfunction indicating nothing at all is amiss, sensor malfunction indicating the sensor didn't like the way my husband replaced the gas cap last time, and sensor malfunction indicating it didn't like several other things that have nothing to do with possible engine malfunctions. It's also a very remote possibility that something catastrophic is about to happen to the engine, but the more we read, the lower that probability appears. As the owner of my second Nissan Sentra--both of which I kept for well over 10 years, and which never tell me anything they don't mean--I am boggled by this non-working device that says everything *except* what it means. For now, we, too, have decided to spend $0.00 to fix it, in our case by doing nothing.

Kevin Shaw
User Rank
Iron
Re: needs replacing SOON, anyway -so-
Kevin Shaw   10/29/2012 1:27:20 PM
NO RATINGS
Hi Bob,

My situation is the opposite. I'm comfortable with the electrical schematics and less so with the mechanical side of things. I warned those "electrically challenged" readers of my posts in the Corvette forum about the dangers of jumpering between fuses in the fuse block.

The ignition switch assembly was in two sections: the actual switch and the keylock cylinder which had the contact to read the resistor in the key. I kept the original cylinder and just replaced the multi-section electrical switch. I found instructions on how to do it on a website that sells service manuals online (not sure if I'm allowed to mention the name of the website in this forum). The instructions on how to take the lower half of the dash apart was worth every penny.

Kevin

Bob Salter
User Rank
Iron
Re: needs replacing SOON, anyway -so-
Bob Salter   10/29/2012 1:00:26 PM
NO RATINGS
Hi Jack,  I have no idea what the black substance was or any way to remove it for analysis, as it all went into the 2000 grit paper. What is interesting is the black coating exacly matched both contacts. The shape of the black on the third contact was a long thin triangle, both contacts. It took very little polishing as the "black" appeared to be very thin, with absolutely no visible pitting. I do know that most "springy" electrical contacts are brass with Berilium alloyed in. Could the "black" be an oxide of Copper, Zinc or Berilium?

Bob Salter
User Rank
Iron
Re: needs replacing SOON, anyway -so-
Bob Salter   10/29/2012 12:51:33 PM
NO RATINGS
Hi Kevin,  I realized a long time ago that I was electrically challenged, which is why I became a Mechanical Engineer who was proud to obtain Bs in EE 101 and 102. So, I'm not conforable reading or understanding wiring diagrams. I do know that the computers in modern cars are controlling more and more auxilliary functions, usually through micro relays. So, after checking the fuse for non-operating function, I think the next thing would be to check the relay. Next would be the ground connection followed by possibly hot wiring the device itself. The root cause of the problem with my Corvette was found in the ignition switch that has to be "on" to supply voltage to many auxilliary circuits. Fortuneately, from a technicians experience and advice, I was able to go directly to the ignition.

When you bought a new ignition switch, did you get the whole assembly with the key/lock mechanism? If so, did you get a key with the same "pellet" resistance?

 

Jack Rupert, PE
User Rank
Platinum
Re: needs replacing SOON, anyway -so-
Jack Rupert, PE   10/29/2012 10:38:11 AM
NO RATINGS
Any idea what the blacik substance was that you were dealing with?  Sounds almost as if you had some bad contactors there.  Glad the switch continued to survive until you got rid of the car.

Kevin Shaw
User Rank
Iron
Re: needs replacing SOON, anyway -so-
Kevin Shaw   10/29/2012 10:11:48 AM
NO RATINGS
Great story Bob. I too had a problem with the ignition switch of my 2001 C5 coupe. While you were doing your research, you may have read my posts in the Corvette forum documenting my troubleshooting and repair . I had posted schematics in the forum to explain the process I went through to find the problem. To confirm the ignition switch was at fault, I jumpered between two fuses on one of the fuse blocks. The problem disappeared and the car functioned perfectly so I took the dash apart and headed off to the Chevy dealer to buy a new switch.

jayprab
User Rank
Bronze
similar
jayprab   10/29/2012 9:37:37 AM
NO RATINGS
I had a Mercury Sable wagon once, probably a mid 90s model, I forget. One day the driver side window switch just stopped working. I called the dealer and he wanted about $600, installed. I went to the local junk yard and they wanted something less, but not by much, indicating that this was a high-failure part and much in demand. So, i decided to at least SEE what might be wrong. I took the switch assembly out and noticed it had CB-point style dry contacts and that these were hefty enough to run the main motor current through. They were heavily pitted and oxidized over, hence the lack of operation. I dismatled the switch so I could clean the points and in doing so noticed that the PCB to which the switch assembly was wired, had pads for spark suppression capacitors on it. They were unpopulated... The engineers HAD foreseen this problem, made provisions to correct for it and the bean-counters (I am guessing) did away with them... I put in caps and NEVER heard from that part of the car again. SEVERAL other things went bad electrically with that car, prompting me to sell it. I always wonder what more was removed as unessential in the interests of cost-management...?

Nancy Golden
User Rank
Platinum
Re: Group knowledge
Nancy Golden   10/27/2012 11:08:34 PM
I agree, Tim - the internet is a HUGE resource. I have used online forums to get information from programming a PIC microcontroller to fixing a plumbing problem to figuring out the best approach when one of my horses decided to misbehave. The first thing I do when I have a question (after I have completed preliminary research) is to search for a forum online to get help. We have to keep in mind that anyone can write anything in cyberspace, but it is usually pretty easy to establish credibility just by using common sense. That was an awesome fix on the corvette thanks to forum help and some initiative on the part of the owner.

tekochip
User Rank
Platinum
Part Swapping
tekochip   10/26/2012 10:36:26 PM
NO RATINGS
I ran the Factory Service Department for an Agricultural Electronics business for a number of years.  Part of the troubleshooting process for many technicians was to replace parts and see if the symptom went away.  I always cautioned against that type of repair and demonstrated scenarios that would result in many parts being replaced without the root cause being found.  Rarely would semiconductors fail, but an unskilled technician would always replace the largest, most complicated component first.  The technician that used an oscilloscope to find the actual failure not only benefited the customer but also the company by finding problems that may have been in the design.


Tim
User Rank
Platinum
Group knowledge
Tim   10/26/2012 8:54:47 PM
NO RATINGS
The internet is a true wonder of communication.  Lately, I have seen use of the internet as one of the best tools in my tool box.  The work of fixing the problem is not hard part.  Knowing how to fix the problem is the big problem.

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