Headlight condensation guidance from HELLA

After unprecedented wet weather, OEM headlamp manufacturer HELLA believes drivers need reminding that fogging or condensation inside lighting units doesn’t usually mean the lamp is defective.

HELLA TECH WORLD has a ‘troubleshooting’ step-by-step flow chart to help garages understand when condensation on the inside of automotive lighting lenses should considered be a concern.

“Moisture inside headlamps can compromise light distribution and also cause corrosion leading to more serious problems or lighting failure,” said Dave Clark, Lighting Product and Brand Manager at HELLA.

Modern headlamps are equipped with ventilation to equalise pressure. When the light is on, heat and expansion will cause some air to be displaced. As the lamp cools down again, internal air pressure reduces, causing saturated humid air from outside to be drawn back into the light interior.

This ventilation means that whilst moisture can enter, it should also escape easily. Visible condensation within lamps is more common in cold, wet or humid weather. This expected condensation should disappear when the lamp is in use. However, when larger water droplets form which do not evaporate, then there may be a problem.
“Water drops on the lens and particularly water gathered in the lower area of the light means the seal must be checked for damage and replaced if necessary,” said Dave. “Ventilation openings should also be checked for blockages and the light can be blown dry with oil-free compressed air. If water still accumulates after this, the unit must be replaced.”

A less well-known cause of moisture accumulating in lighting units is the ‘capillary effect’. This sees water travel down very narrow pathways such as within electric cables. Water ingress into cables usually occurs at a plug connection if the terminals do not offer sufficient protection against humidity.

In the event of problems, HELLA’s flow-chart provides guidance to systematically check key areas including the headlamp fixings, seals, ventilation grommets and wiring. To read the guidance in full please visit https://www.hella.com/techworld/uk/Technical/Automotive-lighting/Condensation-in-headlight-836/.

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