Automotive/signal light problem

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Expert: - 12/21/2007


Question
I have a '92 Chevy Astro Van. V-6 4.3L.
The passenger signal light does not work.  When switched on I hear the clicking really fast or varying speeds. The dash display blinker does not work either.  Both front and rear signal lights are not working.  I replaced both bulbs and no help.  However, as soon as I turn the hazard flashers on it blows the fuse for the Hazards/brake lights.
Prior to this problem my wife said the dashboard "seatbelt" light came on with the signal light indicator when turning, but the signal still worked.  Now no dashboard indicator and no signal light and no "seatbelt" indicator.
I expect there is a short somewhere, but where do I start and how?  I had been working on the heater blower motor which is near the passenger signal light under the hood.  Could my working in that area have done something?

Answer
The most likely possibility is damaged insulation on the wire that feeds the right turn signal lamps.  This is a lead which will be energised whenever the right turnsignals are activated, and also when the hazard warning system is turned on.

If your van uses rear turn signals which are combined with the brake lights (ie: one red rear light on each side for brake and turn signals - true for almost all North American vehicles prior to the early eighties, but used much later in vans and light trucks) and the brake lights continue to work properly, this will further isolate the problem to that lead feeding the right FRONT signal lamp.

Damaged insulation on a lead that is close proximity to or in contact with the body or chassis metalwork will provide a fault path to the vehicle's "ground" (I prefer "0-volt common" because the "ground" definition correctly applies per its electrical code definition which calls upon the earth as a reference.)  Even a brief contact between an exposed energised wire and the chassis would make "short" work of the protective fuse for the signals, and opening that fuse will open the supply circuit for all systems that fuse protects.

The best way to target a problem is to consider what changes or events may have preceded it.  Therefore, going back and checking out recent work is a very efficient place to start.  There is a possibility that a wire got pinched, or a connector got partially separated and something got caught in the gap, or insulation got chafed.  

The good news is that the quick-acting fuse would do its job, that being to protect the wiring (and vehicle) from further damage.  That being the case, once the problem is exposed, covering it up again properly is quite easy.  My preference is any cases involving wire is to cut, trim and resplice it using solder, after first putting on a heat-shrinkable tubing jacket to slide into place and heat seal once the soldering is done.  I use the heat-shrinkable tubing that is lined with two-layer epoxy/hardened system for automotive use.  After that is done, restore the damaged tape cover by tightly wrapping from several inches on each side of the damage with fresh electrical tape, better yet, self-vulcanising tape; this will fuse to itself and reseal much like heat-shrinkable tubing.

Best regards ... 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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