Maintenance Q&A
Light aim and battery drain

By Paul Abelson, Senior technical consultant

I had an accident at a truck stop. A rookie driver backed into my bumper when I was parked. The truck stop's video confirmed what happened. His company's insurance paid for the damage, replacing half my bumper, some brackets and the labor. My Kenworth dealer did the work, and I signed off on it. Since the accident other drivers have been calling on the CB, and four-wheelers have been flashing their lights at me that my brights are on. They're not. It's the aim.

When I went back to the dealer, he wanted me to leave the truck. He said there were trucks that didn't run ahead of me and they had a higher priority. Also, he said since I had signed off on the work, insurance wouldn't cover this. Can I do this myself? If so, how?

First off, you always have the option to contact the insurance company and report additional damage. They can open a supplemental claim and go through the process again to get the additional repairs completed.

But if you are still interested in fixing your headlights yourself, a TMC Recommended Practices Manual will cover the procedures and processes for most problems. It is RP161, Forward Lighting Aiming Methods.

According to the RP, to do it manually, you'll need a vertical wall as wide as your truck. Ideally it should be in a garage long enough to accommodate your truck, but I've aimed my lights outdoors using a schoolhouse wall. Just make sure you can park 25 feet from the wall and perpendicular to it.

Before taking measurements, make sure the truck is level with full fuel tanks, an empty trailer, and properly inflated tires. Clean any mud, snow, ice or salt from the headlamps. Have someone in the driver seat.

Cover each headlight with a large piece of cardboard when you're not working on it. Before turning on your lights, measure the height of each optical center from the ground. Record your measurement.

Subtract 2 inches if you measure between 36 inches and 48 inches, 2 1/2 inches if between 48 and 54 inches. Record your result. On the wall, mark the value and, using chalk or washable crayon, make a horizontal line the width of the truck.

Locate the centerline of the truck, looking through the windshield from the middle of the truck. Have someone mark it on the wall. Draw a vertical line on the wall. Measure the distance between the headlights. Divide by two. Mark each half-distance on the horizontal line, to each side of the vertical line.

Locate the aiming screws on each headlight assembly. Turn the headlights on and cover one with cardboard. For lamps 22 to 36 inches up, the hot spot should be on the horizontal line at the vertical line, give or take 4 inches. If your lights are 36 to 48 inches up, the aiming spot is 2 inches below the line, with tolerance of 2 inches up (at the line) to 6-inches down. For headlights 48 to 54 inches high, the aiming point is 2 1/2 inches below the line with a tolerance of 1 1/2 inches up (1 inch below the line) to 6 1/2 inches down.

There are additional procedures and definitions in the RP, but this should get you going.

I got four new batteries less than two years ago. I went on vacation for two weeks and came back to a set of four dead batteries. I turned off everything I could. What caused the batteries to fail? What can I do to prevent it in the future?

Several factors contributed to your inability to start the truck: parasitic loads and the effects of temperature on batteries and your engine.

Batteries produce less power as they get colder. For starting purposes, the rule of thumb is that a big bore diesel should have 1,800 CCA, cold cranking amps measured at zero degrees. This allows for battery degradation.

Over time surface material from plates becomes flaky because vibration shakes the flakes from the plates. Conventional batteries have wells where flakes can accumulate before they contact and short-circuit the plates. The process starts with the first use and takes a few years until shorting takes place. Meanwhile, performance slowly diminishes.

In cold weather, battery cranking amperage drops. It falls 27 percent from 32 to zero degrees. At the same time, cold weather raises engine cranking requirements. Engine oil thickens, although newer oil chemistry reduces its drag on the oil pump, crankshaft and other parts. From 32 to zero degrees, engines need 50 percent more amps, and even more as temperatures drop further.

When you came back, temperatures in Wisconsin dropped below zero.

You were wise to disconnect your accessories, but it's impossible to remove all electrical loads. Unless you disconnect the ground cable from your battery, you will have some parasitic drain. Some fleets insist that their satellite communications be on at all times. Even internal monitoring systems can drain up to half an amp to monitor systems and keep sensors warm enough to operate.

You were away 16 days, or about 384 hours. Even at only 0.5 amps, parasitic drain would have weakened the batteries by more than half. Most four battery systems start with 328 amp-hours, according to TMC Recommended Practice RP140A, Understanding Key-Off Parasitic Loads. While you were enjoying Florida sunshine, your batteries were discharging.

Next year, disconnect your battery bank from your truck. It may have two ground cables. If so, disconnect both. You said you keep your truck at home, so you can run an outdoor extension cord and connect a trickle charger to the battery, one that turns on and off automatically to prevent internal battery damage. LL