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Automotive/No Brake Lights & Turn Signals Do Not Work.

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Expert: - 9/2/2007


Question
Hi I sure hope you can help with this problem. Vehicle is a '97 Lincoln Town Car. The only Brake Light working is the one mounted above trunk center of rear window. This leads me to believe that my Brake Switch is working OK. When I turn my Headlights on all lights work, front and back. Still no Brake Lights other than previously mentioned. My Turn Signals don't work,either side. The front will come on but not blink. The rear don't come on at all. So I've got no Brake/Turn indicators at rear. Front Turn indicators come on but aren't blinking. All other lights work. I've checked all fuses,underdash and underhood,all OK. All bulbs appear to be OK. Any help/advice is greatly appreciated.  I'm a paraplegia with hand controls. I've been driving this car for a couple of years with no problems. Thanks

Answer
It is quite clear from your own investigation that the Brake Light Switch IS functioning as intended.  It is also quite evident that there is a problem or two with the Turn Signal circuit.  (There is a closing comment on this in my last paragraph below)

One problem likely is the failure of the flasher module; in the majority of cars in my experience, this is a simple three-terminal plug-in module, and it does require replacement on occasion.  When the flasher module fails, the selected turn lights turn on, but do not flash.

The other problem - the absence of the left and right brake lights that also serve as turn signals - points to a separate problem, most likely with the turn signal switch, but also possibly with a harness connector serving these back lights.  The latter problem is less likely, given the proper functioning of the tail lights themselves, however, corrosion problems with connectors will cause successive failures of circuits using that connector.  Corrosion would be caused by the the ingress of moisture and can be exacerbated by electrolysis action if current paths become established through dirt that collects in the connector.  There could be similar problems in the lamp sockets themselves, although the correct functioning of the tail light portion of the 1157 socket (if this is used here) would not suggest that.  The correct functioning of the tail lights also indicate that the "ground" (actually, 0V common) connections to the chassis are okay.

Whatever the problem(s) is(are), the fixes should be straight-forward.  The most likely and best-case scenario would be one in which you replace the flasher module and clean and regrease any connectors that are questionable.

Please note that the above is GENERAL.  As indicated in my notes, I have wiring diagrams and shop information ONLY for my own vehicles, and cannot speak to specifics that may apply to your 1997 Lincoln.  If I were in your place, my first action before doing any but the most basic trouble shooting would be to get the wiring diagrams and/or shop manual.  Going in informed and without making assumptions that may not apply is a tremendous time saver and the most effective tool in solving present problems and in heading off future ones.

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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