Automotive/Headlight problem

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Expert: - 2/8/2008


Question
Hello
I own a '99 Grand Am, and I'm having a very odd headlamp problem.. When I turn my brights on my driver's side is bright and my passenger side is dim, but when I have my dim lights on my driver's side is dim, and my passenger side is bright. Any help would be appreciated. :)  

Answer
Well, whatever the problem is, it would appear NOT to be a problem with the headlight "ground" circuit, inasmuch as that ground is shared by both filaments in the H4 or 9004 or even old tungsten sealed beam or whichever lamp your car uses.  (On the other hand, if both High and Low on ONE side only were dim, the ground on that side would be the first thing I would check out.)

That being the case, the problem would appear to be one more generally associated with connector aging, or burning and pitting of headlight contactor contacts, in more than one place in this case.  I do not know the Grand Am's wiring details, but think it likely that there are two points of high-resistance in your circuit, one in your driver-side low-beam circuit, and the other on the passenger-side high-beam circuit.

Getting the wiring diagram in order to check out the circuits completely is always a good idea.  In the short term, why not pull each of the headlight relays (I call them "contactors" as that is the correct term for a relay with load-rated contacts) and check the terminals for signs of heat damage - discolouration and pitting - and or corrosion.  Check both the contactor terminals and the socket terminals with which they mate.  If the damage is only slight, it is possible that you can restore proper operation by simply cleaning both socket and relay terminals and applying electrical contact grease before reconnecting them.  Worse or very obvious damage will call for replacement of the contactor and/or the termination socket as a matter of course.

The problem might also be due to damaged wiring due to some misadventure.  Again, having the wiring diagram would facilitate doing a thorough checkout if that is needed.

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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