§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
Wiper findings on a DVIR link to the vehicle record and surface as a §396.11 unrepaired-defect item until repair certification is filed. The audit binder retains the DVIR with the defect documented and the repair date proven.