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Question
I have a 1990 GMC 1500, 5.7
When it gets cold out my headlights sometimes take up to half an hour to turn on.
My dash lights and parking lights come on as soon as I turn on the switch but not my headlights.
Any thoughts?
I live in Vegas. It gets in the 30's at night.
Thanks,
Bob
Your comment about cool night-time temperatures (that is 30F, I presume, and not 30C!) indicates that you have a pretty fair idea of what the problem might be, and I am inclined to agree with you.
The impression here is that there is a loose connection that must warm before it conducts. There is a broken bond of some type in which two disconnected ends must expand until they connect and allow the current to flow.
This is more likely a connector problem or a component problem than a wiring problem. Flexible stranded wire will break open within its jacket only if it is physically cut or if it burns open by fusing action. Aside from either scenario being easy to find via visual inspection, neither of them would provide any means for conductivity, intermittent or otherwise, once the wire was opened.
There could be a problem at a connector. In general, automotive wire is crimped within a connector, and the bond portion is thereafter sealed within rubber or similar insulation. If the seal breaks, capillary action can draw in moisture which can, over time, cause oxidation of the connection, and thus increase its resistance. The higher resistance causes localised heating, which then has the effect of expanding the joint. Copper has a higher rate of expansion than iron and nickel and other materials used to fabricate connectors, so the copper conductor can be expected to expand into a tighter fit with the connector containing it, hence re-establishing a low-resistance connection.
Connectors that are both crimped and soldered (which is what I generally do) are less likely to develop the above problem, but can be susceptible to breaks in any section of the stranded copper wire which has been solidified by excess solder. Proper solder practice means avoiding excessive "wicking". Wicking is the process whereby solder is drawn up within which is a process whereby solder is itself drawn up by the gaps between the stranded wires. This seals out moisture and makes an excellent alloy bond, but too much solder will allow solder to be drawn into the wire beyond the connector, removing the flexibility of that section and rendering it brittle, and thus easy to break. This would create another possibility for a thermally-sensitive connection.
Components in which contacts could develop thermal sensitivity include headlight and dimmer switches, and lighting relays, if used.
A good mode of finding any such problem (after carrying out a visual inspection for anything obvious) is to use canned "Freeze-Mist" or any similar electronics industry-type fast cooler. The circuit is first made to work, ie: turn on your light switch and wait until the lights are on, and then, one suspected site at a time, spray the mist so as to thoroughly cool the joint or component until the lights go off a again. Cooling would have no effect on properly bonded connections, but will separate any that are held together only by thermal expansion.
Happy hunting (and New Year, while we are at it!) ... EGK
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Answers by Expert:
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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