§393.78(a) requires every CMV to be equipped with two power-driven windshield wipers, one on each side of the centerline, both in operating condition. A single inoperative wiper is the §393.78 finding. The wipers must clear the windshield through their normal operating arcs at the speed appropriate for prevailing weather.
Severity
Severity weight 1 — low. The compounding risk is in heavy weather: an inoperative wiper that the driver knew about under §392.7 pre-trip pairs with the §392.7 driver finding, and if an accident results, contributory-negligence exposure is real.
How to prevent it
- DVIR pre-trip includes wiper test in both speed positions.
- Replace blades on a calendar interval (every 6 months for high-mileage operations).
- Stockpile wiper-arm components in the maintenance shop — wiper-motor failures usually surface as full-wiper-side failures, not as blade wear.
How Roadworthy HQ helps
A wiper citation shows up in Roadworthy HQ as part of the inspection it came from, not as a record of its own: the app does not store individual violation codes. Log the roadside inspection on the vehicle's Inspections tab: date, state, level, driver, the number of violations, and whether it was out-of-service. For an out-of-service inspection the 15-day §396.9(d)(3) repair-certification countdown stays on that tab until you enter the certification date. The rule's 15 days cover every violation on the report, not only out-of-service ones, so for a non-OOS inspection that date is yours to track. The repair itself goes in the vehicle's maintenance log: date, type, what was done, who did it, and cost. DVIRs are logged per vehicle with the defect described in your own words, and a defect marked safety-affecting that is logged without a repair certification sends a critical alert.