Xenon headlights — overcoming a glitch to get consistent brightness.

High Intensity Lights

Motorhome headlights have come a long way from the days when a switch wired to an incandescent bulb was the accepted configuration. Today, halogen, H.I.D. (High Intensity Discharge) and L.E.D. have replaced those dinosaur bulbs.

Many RV manufacturers favor H.I.D. product (Xenon). While these super-bright lights offer some nighttime visual benefits, their operation is very complex: They’re powered by an individual control ballast resistor for each light. These ballasts spike around 2,000 volts at start up and then must maintain a steady 85 volts or higher while illuminated.

This complexity can make what seems like a simple fix anything but. The simple job of replacing a bulb first requires some troubleshooting to determine the issue.

Troubleshooting the Problem

If a lamp fails to light, we may assume the bulb is burned out. On the other hand, it may not be the bulb, it might be a failed control ballast. To further add to the confusion, the light may work intermittently. Merely toggling the headlamp switch may again bring it back to life.

First, do not run out and buy a new bulb just yet. They are quite expensive and it very well may not be the lamp.

Unplug and remove both ballast units and switch their position left to right/right to left and reconnect. Turn on the headlamps and observe if the inoperative light is now on the other side. Toggle the lights on and off if the original issue was intermittent.

If the opposite light is now inoperative the failed side ballast must be replaced. If the same side is still the culprit, we will have to now switch the bulbs from one side to the other. After this, retest the lights, again toggling the switch if an intermittent failure was the original issue.

Oddly enough, in the case of an intermittent failure, you would think the fault would lay in the ballast. But, in many cases this is not true. A faulty bulb can intermittently exhibit an incorrect start up current draw which the ballast senses and shuts down for safety.

The Devil in the Details

Some notes to keep in mind. Do not handle the H.I.D. bulbs with bare fingers. Use a cloth or gloves to avoid leaving skin oil on the surface. Make sure whichever component you replace is exactly the same part number. There are quite a few different models and they are not interchangeable.

For maintenance of headlights and other devices, check out Camping World.

Peter Mercer — Shedding Some Light on H.I.D. Service