Date: Thu, 15 Apr 2010 10:54:29 -0500
Reply-To: mcneely4@COX.NET
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dave Mcneely <mcneely4@COX.NET>
Subject: Re: Now Preventative Maintenance, Was Do U carry spare ECU?
In-Reply-To: <t2s86476e251004150827lbddcad31peed6484eb8006afb@mail.gmail.com>
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Well, the data as you report them makes a case for both NOT doing preventative maintenance on electrical circuitry, and FOR doing preventative maintenance on such circuitry. If most failures are due to corrosion, loose connections, broken pins and such, then it makes sense to clean up, tighten up, and replace. If failures are due to operator error (breaking things, leaving things loose, maybe spilling liquids that cause corrosion), then it makes sense to leave things alone.
My tendency has been to leave many things alone that are working, but for things where the consequences of failure are serious, to do preventative maintenance. Of course, the quality of the interference is all important. I suspect that the average sailor in the study was just trying to get through his enlistment without too much grief, rather than trying to be the best technician he could be. I mean this as no indictment of sailors, but it is an observation on human nature, whether seafaring or otherwise.
Not being a talented mechanic (being somewhat undisciplined and impatient is the probable cause of this condition), I generally hire work done. I spent a lot of time, grief, and money trying to track down an oil pressure "problem." More than one tech failed to clear up the problem, yet it didn't seem reasonable that my rebuilt engine with less than 30K miles was worn out, especially since it ran so well.
I personally found then that a connector to one of the sensors wiggled and I could alter the oil pressure reading by playing with it. That lead to further investigation of the wiring, sensors, and gauge that the previous owner had installed. Got it to a competent mechanic who found that the gauge and sensor were mismatched, and the wiring was poorly installed. He installed a matched gauge and sensor, tightened everything up, and replaced the wire to the instrument cluster. Oil pressure monitoring is excellent, and oil pressure is right on spec (as per both my gauge and my mechanic's large dial pressure (as opposed to electrical) gauge.
Maintenance is essential, but it has to be done by folks who know what they are doing, care, and exercise that care. Ignorance is expensive, too. I spent money that I need not have spent on this problem before finally getting it resolved. I also worried unnecessarily about it.
DMc
---- Loren Busch <starwagen@GMAIL.COM> wrote:
> On Thu, Apr 15, 2010 at 7:47 AM, mark drillock <mdrillock@cox.net> wrote:
>
> > It is a fine theory to say replace things in advance of their failure
> > but experience shows that the replacement parts are often what fails
> > these days. Whether that is due to declining parts quality or lack of
> > workmanship in the replacing, I'd say some of both.
> >
>
> Mark has a good point here. In the 1950's the US Navy did a study on the
> value of 'preventative maintenance' on electrical and electronic devices.
> This was back before printed circuits and solid state electronics. Most
> control and switching circuits were relays and many of the relays were open,
> not encased, like in cross bar switches. And regs at the time called for
> periodic cleaning of the relay contacts. They found that their down time
> and failure rate dropped dramatically when they quit doing the cleaning,
> only cleaned (reads 'messed with') things when there was a failure or
> malfunction. The process of doing the preventive maintenance was causing
> more problems than it was preventing. Later studies confirmed this for
> other electrical and electronic devices. They also arrived at the
> conclusion that 80% or better of failures in electronics (especially after
> the introduction of solid state devices) was mechanical in nature, bad
> connectors, corroded connectors, broken pins, poor contact, etc.
> Now, how many times on this list have we read about problems arising right
> after work has been done or parts replaced? And how often have various
> problems been diagnosed as loose connections, corroded wires and plugs and
> connectors, corroded gronds, etc? The mechanical part of the equation.
--
David McNeely
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