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Oldsmobile flashes lights when it's least expected

Automotive EquipmentManufacturing and EngineeringGeneral Motors

QUESTION: The headlights on my 2002 Oldsmobile Silhouette turn on and off unpredictably, whether it's running or not. All lights work properly otherwise. I have to remove the headlight bulbs while parked to save the battery.

ANSWER: In a follow-up communication, George verified no other lights were remaining on when the Olds is parked. I wanted to be sure, as there can be some confusion between misbehaving daytime running lights, which are headlamps only, and automatic lights, which are head and parking lamps. After looking over the wiring diagrams for this vehicle, it appears the only way this symptom could occur would be due to a fault within the daytime running lights, or DRL, control module. There is no other path between battery power and the headlamps with the key off, other than through this box. A faulty input signal to the control box is possible, but unlikely.

The DRL control module is located under the left side of the instrument panel; it's fairly easily accessed after removing the under-dash hush panel. Parts availability may be tough, other than via a recycled part from a wrecking yard. Another option, and it's an easy one, is to put the DRLs out of their misery by removing the blue 10A DRL fuse from the passenger-side instrument panel fuse box.

Q: The left-side daytime headlight on my 2007 Chevrolet Silverado stopped working and looks terrible this way. How is this fixed? Can I do it myself?

A: This couldn't be easier. General Motors did a nice job making the daytime running lamps accessible for service. Good thing, too, as the bulbs don't seem to last anywhere close to their 4,000-hour rated lifespan.

With the hood open, locate the horizontal "L" pin atop the headlamp housing. Rotate/unlatch the L to allow the pin to be wiggled inboard and removed completely. The headlamp housing can now be lifted up and away from the body and set aside; unplugging headlamp connectors is preferable to letting the housing dangle.

The DRL lamp is now readily accessible below the vacated space. Press in on the small tab and rotate the lamp socket to disengage it from the housing. The bulb can now be removed and renewed. Plan ahead and purchase two 4114K bulbs before disassembly, and do both sides they're about $3-$4 apiece. The 4114K bulb is a longer-lasting replacement for the often-cursed 4157K bulbs used in pre-2003 GM vehicles. Reassembly of the parts is the opposite of disassembly.

I'd also pick up a small tube of dielectric grease and smear a dab around the base of each new bulb. These bulbs, because of their continuous duty cycle while driving tend to make the plastic socket a little crispy. The dielectric grease reduces corrosion and I believe helps transfer heat more evenly from the bulb to the socket, likely increasing bulb and socket longevity.

Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose, Calif. Readers may send him email at; he cannot make personal replies.

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Copyright © 2014, The Baltimore Sun
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