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Automotive/Digital Instrument Panel

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Expert: - 8/21/2007


Question
Hi Ernie! Not sure if this is in your league or not,but thought I would try due to your knowledge in electrics.I have a chevy astro van,1994, that my digital instrument panel decided to go out on me. Had recently got the van & had a fellow do a tuneup & change battery terminals. Got in it that nite;panel was all black.Could'nt see a thing.      He fixed it next day. How I don't know & I can"t find him again.2 weeks later I had an altenator put in.Got in that nite,guess what?,yep,no guages to be seen. It's not fuses. This may be a stupid ?,but would it have anything to do with disconnecting electrical supply both times? Have any idea? Thanx for your time, Gail.

Answer
Happy to help!  Btw, I never took food prep in high school, but play a lot with (con)fusion cuisine anyway ... Mediterranean/Thai/Indian multinational mixes.  Keeps life interesting!

Cheers ... EGK

Note that I do not have specific details on your van, nor on any vehicles other than those I own, in fact.  However ...

I wonder if the problem is an intermittent electrical connection, most likely an intermittent "ground" or connection to the vehicle negative common.  Inasmuch as everything else works properly, including all services that draw any significant current, the affected connection would have to be one of the ones used by the instrument panel.

The good news at least is that an intermittent connection, once found, is usually a very easy problem to fix.  A proper fix, by the way, would be one in which connectors are inspected, replaced if corroded or cleaned if okay, and lubricated with electrical contact grease in either case before reassembly, the overall idea being to find and eliminate the problem.  It seems that the tech who initially worked on your van tweaked things around until the panel worked again, and left it at that.  A good start this time would be to take related connectors apart and subject them to the regimen suggested above.  

It is also possible - but much less probable unless physical damage is visible - that a wire may be broken within a harness.  Breaks or intermittent wires can be found by opening connectors to isolate the harness a section at a time and moving and bending the wire leads while monitoring continuity of each wire between the ends of each section using an ohmmeter on low-ohms range, continuity beeper enabled.   

Any service tech doing this work would have access to the wiring diagrams, either from the OEM shop manuals or from Mitchells on-line; having the correct data focuses the efforts and saves time.

My bet is on an oxidised connection - this is increasingly common as a vehicle ages.

Good luck ... EGK

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Ernest (Ernie) Kenward

Expertise

The challenges I most enjoy are thoughtful technical questions of a trouble-shooting nature in both electrical, power electronic and mechanical systems, mainly automotive but also machine control and small-machine PLC applications. Please note, however, that I am NOT a walking shop manual! I DO, however, make it a point to have those manuals and other service literature for those vehicles I DO own, and highly recommend that anyone serious about maintenance or modification of their vehicles do the same; MOST of your answers WILL be found there. For that matter, I do NOT go out of my way to acquire shop manuals for any vehicle I do NOT own! That being the case, any general query to me along the lines of "What is the meaning of this code read from the ECU of my 2015 XYZ?" or "Where is the fuse for the windshield washer pump found?" (try your car's electrical distribution panel for a start!) will not go far. What I do offer is a pretty good collection of literature, insights and hands-on experience with 1950s to 1980's Ford products (plus a developing database of information and practice with the Mercedes diesel cars), along with an engineering perspective and the ability to design and implement custom control, electrical and mechanical subsystems for vehicles. For that reason, I am happy to make my thoughts and efforts available to those who are of like mind and/or are seriously making a point of learning about their vehicles. Use the Opportunity to Learn!

Experience

A key skill in my work and hobby pursuits both is STRATEGIC TROUBLESHOOTING. I am a senior instructor in Electrical Engineering Technology at a leading Canadian polytechnic, my areas being Electrical Power and Industrial Control, electrical and electronics design and manufacturing, and AutoCAD and related CAD/CAE software - plus equipment problem-solving and new equipment design and prototyping. Hobby-wise, I have 30-plus years of experience in auto restoration, mostly in electrical and mechanical systems. Ongoing projects include a 1959 Edsel Corsair, my 1978 Ford E250 class-B motorhome conversion, and the care and upkeep of my Mercedes 300CD. My vehicles become engineering test beds for electrical and mechanical upgrades as ideas present themselves. This includes the design and production of circuit boards to restore or enhance features for which no OEM replacement parts are obtainable, or where better specifications or reliability can be had via newer concepts. Regarding the E250 RV conversion, I designed and continue to revise a custom power distribution system, managed by a Programmable Controller (PLC); this has made most revisions as easy as uploading new firmware as I develop it. The "mini" PLC is a powerful device for custom automotive control systems. One good example (there are many) would be the Moeller "Easy Relay"; these offer a wealth of control, monitoring and variable-and-status display options for such projects. A good example project which has worked well is that one for my RV noted above, which has been on the job - revised in firmware only - for a decade now. It is a load management and charging control system to avoid the sulfation-induced early failure that often befalls deep-cycle batteries used in RV power applications. The battery installed in 2003 lasted long enough to more tnan pay for the PLC that contributed to its longer life ... and the PLC will be there for the next battery as well!

Organizations
IEEE - senior member ... past WCC Student Activities; SME - senior member ... past chair, greater Vancouver chapter chair 318; Edsel Owners' Club - have served in various capacities on chapter executive during seventies; have been Power and Driveline resource on the Edsel Owners' Club "E-team" for more than a decade.

Education/Credentials
Graduate of UBC

Awards and Honors
Certificates of appreciation from IEEE and SME for work in student and chapter activities

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