The headlamps on 2010 through 2017-model GMC Terrain SUVs put out too much upward stray light on low beam, and NHTSA have denied GM’s petition to consider the noncompliance inconsequential. That denial means GM will have to recall and repair the cars.
The headlamps are Stanley items, and the problem stems from light bouncing around in the space between the projector low beam’s condenser lens and the headlamp housing’s front cover lens. Some of this light hits a shiny spot on the bezel, and the reflection creates a streak of upward stray light with intensity of just under 500 candela, about 80 degrees outboard and 45 degrees above horizontal. The low beam intensity limit in FMVSS № 108 is 125 candela from 10 to 90 degrees above horizontal.
GM argued in 2019 that the stray light was inconsequential to safety because it was well outside the equipped driver’s gaze field; its angle made it highly unlikely to affect other drivers; the lamps meet SAE J1383 and ECE R112 requirements for light in that angular region; only a single customer had mentioned noticing the stray light and GM wasn’t aware of any resultant crashes or injuries, and revised replacement parts have a coarser texture to the part of the bezel reflecting the stray light. NHTSA swatted away these arguments, stating that the SAE and ECE standards are irrelevant to a question of compliance with FMVSS108; the over-limit stray light does have the potential to zap other drivers in bad weather; the lack of any crashes so far doesn’t mean there won’t be any in the future, and the availability of compliant replacement parts doesn’t address the noncompliant parts on the road.
The agency noted that inconsequential noncompliance is most often a finding applied to fiducial aspects of compliance—labelling, marking, and other suchlike—rather than performance aspects, and last week denied GM’s 2019 petition, so the automaker will have to recall about 725,000 Terrains in the United States and fix them so they comply, at no cost to owners.
