393.78 Violation: What It Means and How to Fix It
Data through September 24, 2026 · Last updated October 28, 2026 · By Chad Griffith, founder
Quick Answer
393.78 (Windshield wiping and washing systems) was cited 27,377 times in roadside inspections of interstate for-hire carriers with 5 to 50 trucks from September 25, 2024 to September 24, 2026, and 0.2% of those citations put the driver or vehicle out of service. The most common version is 393.78A-WS: Washers - Inoperative washing system..
27,377
Citations on carriers with 5 to 50 trucks
0.2%
Out of service
174,738
All carriers, same period
What the rule says
Power units must have working windshield wipers and a working washing system (49 CFR 393.78).
When it puts you out of service
Not out of service here; a quick fix that small carriers are cited for often.
The codes on the inspection report
| Code | What the officer wrote | Severity weight | Citations, 5 to 50 trucks | Out of service |
|---|---|---|---|---|
| 393.78A-WS | “Washers - Inoperative washing system.” | 1 | 15,129 | 0.0% |
| 393.78 | “Wipers - Inoperative / missing / damaged wipers” | 1 | 12,138 | 0.1% |
| 393.78-WOOS | “Wipers - Inoperative/missing/damaged on drivers side during inclement weather requiring use of the windshield wipers” | 1 | 110 | 40.9% |
How it scores (violation points)
How it scores: in FMCSA's Safety Measurement System each violation counts its severity weight, plus 2 if it put the driver or vehicle out of service, times 3 in its first 6 months, 2 from 6 to 12 months, and 1 from 12 to 24 months. FMCSA has approved a simpler scale that is not live yet.
How to fix it
- Replace worn blades or a failed washer pump and fill the reservoir.
Stop it happening again
- Wipers and washer fluid on the pre-trip checklist.
Challenging it in DataQs
Use DataQs (dataqs.fmcsa.dot.gov) only when the report is wrong: the wrong carrier or vehicle, a violation that did not happen, or a citation a court dismissed without a fine or found you not guilty of, which removes it from the Safety Measurement System; a conviction of a different charge lowers its weight to 1 (FMCSA adjudicated citations policy). Fixing the defect afterward is not a reason to remove it; keep the repair record instead.
FileFlo reads your public FMCSA record, lists every violation with the rule behind it, and keeps the driver and vehicle records that stop repeats.
Run it yourself: the Audit-Ready Setup, $499 through December 31, 2026, then $199 a month for up to 15 trucks. Or FileFlo runs it: $1,500 a month for up to 15 trucks, Setup included, and your first month back if you are not happy.
About these numbers
Counts are violations cited in roadside inspections used in FMCSA's Safety Measurement System from September 25, 2024 to September 24, 2026 (dataset 8mt8-2mdr on data.transportation.gov, October 2026 run). Carriers with 5 to 50 trucks means 66,936 active interstate for-hire carriers with 5 to 50 power units and more trucks than buses, based in the 50 states or DC, from FMCSA's census file. This is FileFlo's reading of public FMCSA data, not an FMCSA rating. Severity weights are the current SMS weights.