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Automotive/Chev Venture Headlights flickering

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Expert: - 1/11/2008


Question
I own a 2002 Chev Venture (extended - 3.4L). While driving lately out of the blue the lighting system turns off. Once for a brief second, couple other times for a 5 or so seconds.  The whole lighting system turns off, including dashboard, radio lights and taillights. The car stills runs ok during. It does have a photo sensor, but when I tried to manually turn on it wouldn't keep the lights on during the problem.  If I manually hold the high beam I can still get light.  It eventually goes back on.  Nothing unusual happens like bumps or wet or dry. I have had my mechanic look at it, left it on for over an hour (never reproduced the problem).  I have took the headlights & corner lights out and looked for a short in the wire - couldn't find it or reproduce the problem.  I checked the ground and couldn't find a problem.  Don't want to blindly replace stuff like the headlight switch or the photosensor.  Any suggestions?

Answer
The fact that not only the headlights go out, but also the tail lights and instrument lights, suggests that there might be an intermittent opening of the power supply to the headlight switch.

Your most productive step at this point, inasmuch as you are taking steps to troubleshoot the problem, would be to get a copy of the vehicle's wiring diagram(s) so that you can go through the system systematically.  (Note that I do not and would not be expected to have any such information on your vehicle so I cannot advise you directly, but I do maintain a comprehensive set of documentation on all my vehicles, plus I log all problems and/or changes, and I recommend this practice highly.)

One thing you might consider: I would expect that the Venture uses automatic-reset thermally-activated circuit breakers for the headlight circuits, which has been the typical approach in North American vehicles over the years.  If that is the case, your problem may be due to thermal cycling of a master circuit breaker for the lighting system, either feeding or perhaps integral with the headlight switch.  Earlier Fords had these, and one of the problems with that system was intermittent loss of lighting brought about, NOT by any short circuits or other wiring issues, but by simple aging of the circuit breaker and attendant increase in contact resistance causing the breaker to heat up and then open.  Because the breaker was an autoreset unit, the lighting would reconnect as the CB cooled, and then trip off again as it heated again.

I solved this problem in both of my Fords by amending the circuit so that the switch drove headlight contactors rather than the lights directly, and further modified and coordinated the protection scheme so as to provide overlapping redundancy in the lighting circuits, ie: each light individually protected so that any problem would be isolated to one light only.  (Since doing this twenty years ago on my E250, I have had no causes for CB tripping whatsoever.)

We agree that there is no point in blindly replacing anything.  Get the wiring diagrams and the information about the components, and take it from there.  If the headlight switch includes an integral CB, you may have found a problem that gentle heating with a hair dryer preferably or an industrial hot-air gun VERY CAREFULLY might verify.

Good luck and happy hunting ... 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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