Shining See

The new composite headlamps truckmakers use these days are paying off in far better reliability than the old sealed beam units. Shoot, the ability to change a bulb using just a screwdriver is a plus. And since replacement bulbs are widely available and can fit into a glovebox, these new-generation lamps have a lot going for them. Here are six tips to make sure you get the most out of them.

1. Look for matching part numbers for replacement bulbs by cross-referencing factory or original equipment components with aftermarket suppliers’ parts. Go for a recognized brand-some automotive bulbs now fit trucks but only heavy duty bulbs stand up to the rough and tumble of trucking.

2. Keep your hands off the glass when replacing halogen bulbs. Don’t touch the glass envelope: though headlamps are pretty robust, the oil from your hands can affect the bulb’s ability to dissipate heat, reducing service life. Keep the bulb protected in its cardboard carrier until it is installed, and handle it only by the back or the connectors.

3. Lube the terminals with a petroleum-jelly type of dielectric lubricant when reassembling the fixture. The goo will generally delay the ingress of water. Also, separate the headlamp connectors twice a year to clean the terminals and reapply a dollop of the jelly.

4. Keep the schematic nearby. For instance, if the high beam fails on both sides, but the dip and the high-beam warning light are functioning, it’s unlikely both high beams have failed. A quick study of the schematic will narrow down the likely areas to about a quarter or less of the headlamp wiring circuit for much quicker identification of the problem.

5. Use high-tech wire-chasing transmitter/receiver tools to check for continuity when troubleshooting a failed circuit. A light probe is OK, but some technicians use the sharp end of the probe to dig into the insulation and check for continuity of the circuit. Doing so will leave a pinhole in the plastic. Water-or worse, salt water from winter roads-will get in and wick down the wire. A year down the road, this will disintegrate the copper inside. These failures are very hard to track down.

6. Set your lamps correctly. Designated an area at the terminal where the beam pattern can be checked against a marked target. This is probably a chore to most mechanics, but it’s a big issue for drivers.