This checklist covers standard DC motors in non-critical applications. For production-critical DC motors where unplanned failure means extended downtime or long lead times, see the DC Motor PM Checklist — Critical.
⚠️ Disclaimer: These tasks are guidelines only. They do not include lockout/tagout (LOTO), energy isolation, or other safety requirements. Review and verify suitability for your specific equipment and application. Add all required safety procedures per your company's policies and regulatory requirements before use. You are responsible for the safe and appropriate execution of all maintenance activities.
DC motors fail in ways AC motors don't. The commutator wears. Brushes erode. Carbon dust accumulates in places it has no business being. And most of those failures announce themselves weeks in advance — if someone is actually looking.
This checklist covers standard DC motors in non-critical applications. It's written for maintenance technicians executing the PM and maintenance managers building or auditing a DC motor PM program.
For the full picture on what a DC motor PM program should be doing: electric motor preventive maintenance
How to Use This Checklist
Record specific findings — not checkmarks. "Brush length: 32mm, minimum 25mm, not yet replaced" is a record. "Brushes OK" is not. The value of this checklist compounds over time only if what you're entering is real data. A good finding sounds like: "Commutator surface smooth, uniform dark patina, no pitting or grooving." A bad finding sounds like: "OK." One is maintenance. The other is paperwork.
Field Checklist — Critical Tasks
8–10 highest-consequence tasks for technicians executing the PM. Action-oriented. Organized for efficient field use.
Visual Inspection
| Task | Freq | Type |
|---|---|---|
| Inspect motor exterior for signs of overheating, discoloration, cracked housing, or physical damage. Note any abnormalities. | Every PM | MEC |
| Inspect motor ventilation openings for blockage. Clean screens, guards, or fins of dust, debris, or lint buildup to ensure adequate airflow. | Monthly | MEC |
Operational Checks
| Task | Freq | Type |
|---|---|---|
| Check motor nameplate and verify operating voltage, current draw (using a clamp meter), and speed are within nameplate ratings. | Every PM | ELE |
Mechanical Inspection
| Task | Freq | Type |
|---|---|---|
| Verify motor coupling or drive connection for looseness, wear, or misalignment. Check set screws, keyways, and flexible elements as applicable. | Every PM | MEC |
| Check motor bearings for noise, vibration, or roughness while running. Lubricate per manufacturer interval and specifications — do not over-grease. | Semi-Annually | MEC |
Electrical Inspection
| Task | Freq | Type |
|---|---|---|
| Inspect brush holders and carbon brushes for wear. Measure brush length and replace if worn beyond the minimum length marked on the brush or per manufacturer spec. | Monthly | ELE |
| Inspect commutator surface for pitting, grooving, scoring, or uneven wear. Surface should be smooth and have a uniform dark patina. Flag abnormal wear for follow-up. | Monthly | ELE |
| Clean commutator and brush rigging of carbon dust using dry compressed air or a vacuum. Do not use solvents on the commutator. | Monthly | ELE |
| Check brush spring tension on all brush holders. Tension should be firm and consistent across all brushes. Replace springs that are weak, cracked, or uneven. | Quarterly | ELE |
| Inspect all electrical connections at the motor terminal box — check for looseness, corrosion, or heat discoloration. Torque to spec and clean as needed. | Annually | ELE |
Reference Checklist — Full Task Library
Comprehensive task library for maintenance managers building or auditing a DC motor PM program. Pick-and-choose format. Select tasks appropriate for your equipment, environment, and failure history.
Visual Inspection
| Task | Freq | Type |
|---|---|---|
| Inspect motor exterior for overheating, discoloration, cracked or damaged housing, and physical damage. Record any abnormalities and compare to prior PM notes. | Every PM | MEC |
| Inspect motor ventilation openings, screens, and cooling fins for blockage from dust, lint, or debris. Clean to ensure unrestricted airflow. Confirm cooling fan (if integral) rotates freely. | Monthly | MEC |
Operational Checks
| Task | Freq | Type |
|---|---|---|
| Measure and record motor operating current on all applicable leads using a clamp meter. Compare to nameplate FLA and prior readings. Investigate any upward trend or values exceeding 105% FLA. | Every PM | ELE |
| Measure and record operating voltage at the motor terminal box. Verify within ±10% of nameplate voltage and balanced across leads if applicable. | Every PM | ELE |
Mechanical Inspection
| Task | Freq | Type |
|---|---|---|
| Inspect motor coupling or drive connection for looseness, wear, cracking, or misalignment. Verify set screws and keyways are secure. Flag any flexible element degradation. | Every PM | MEC |
| Inspect armature end play and check for any axial movement beyond manufacturer tolerance. Excessive end play may indicate bearing wear or a loose thrust collar. | Quarterly | MEC |
| Inspect motor mounting hardware — base bolts, foot pads, and anti-vibration mounts. Check for looseness, cracking, or deterioration. Retorque fasteners to spec. | Semi-Annually | MEC |
Electrical Inspection
| Task | Freq | Type |
|---|---|---|
| Inspect all carbon brushes in each brush holder. Measure and record brush length; replace any brush worn to or beyond the minimum service length per manufacturer spec or site standard. Replace brushes as a complete set when any single brush requires replacement. | Monthly | ELE |
| Inspect commutator surface condition. Look for pitting, grooving, threading, flat spots, or uneven wear. Surface should be smooth with a uniform dark patina. Raised or depressed mica segments should be flagged for undercutting. Document findings. | Monthly | ELE |
| Clean commutator, brush holders, and brush rigging using dry compressed air or a vacuum. Remove all carbon dust accumulation. Do not use solvents on the commutator surface. | Monthly | ELE |
| Inspect brush holders for cracks, heat damage, or carbon buildup in the brush box. Verify brush box-to-commutator clearance is within manufacturer spec (typically 0.060"–0.090"). Clean or replace holders as needed. | Monthly | ELE |
| Check brush spring tension on all brush holders using a spring scale or by feel. Tension should be firm, consistent, and within manufacturer spec (typically 2–6 psi on brush face). Replace springs that are weak, cracked, distorted, or inconsistent. | Quarterly | ELE |
| Inspect brush pigtail connections (shunt leads) on each brush for fraying, burning, or loose crimps. Replace any brush with a damaged or missing pigtail. | Quarterly | ELE |
| Inspect, clean, and re-torque all electrical connections at the motor terminal box. Check for looseness, corrosion, heat discoloration, or damaged insulation. Apply anti-oxidant compound to aluminum connections if applicable. | Semi-Annually | ELE |
| Perform a full internal inspection with motor de-energized and LOTO applied. Inspect armature windings for discoloration, cracking, or contamination. Check field coil connections and insulation condition. Blow out interior with dry compressed air. | Annually | ELE |
| Check and record brush neutral position. Verify brush rocker ring is locked in correct neutral position. Shift in neutral can cause sparking, poor commutation, and accelerated commutator wear. | Annually | ELE |
Lubrication
| Task | Freq | Type |
|---|---|---|
| Lubricate motor bearings per manufacturer specifications — type, quantity, and method. Do not over-grease. For grease-purge type bearings, run motor briefly after greasing to purge excess. Record lubricant type and quantity applied. | Semi-Annually | MEC |
| Listen and feel for bearing noise or roughness while motor is running. Check for elevated bearing housing temperature using a contact thermometer or IR gun. Bearing housing temp should not exceed ambient + 40°C or manufacturer limit. | Semi-Annually | MEC |
| Review and trend all recorded data from this PM period — current draw, brush lengths, bearing temperatures, and any defect history. Identify any deteriorating trends and adjust PM frequency or scope as warranted. | Annually | ELE |
Failure Modes This Checklist Targets
Brush Wear and Seating Failure Carbon brushes wear continuously in normal operation. When they wear unevenly, lose proper seating, or run at inconsistent spring pressure, arcing begins — and arcing destroys commutator surfaces far faster than normal wear ever would.
Commutator Surface Degradation Pitting, grooving, mica protrusion, and flat spots disrupt the electrical contact that DC motors depend on. Most commutator damage is progressive and preventable if someone looks at the surface on a monthly basis.
Carbon Dust Accumulation Carbon dust is conductive. Let it build up in the brush rigging, around the windings, and inside the terminal box, and it creates leakage paths that quietly degrade insulation resistance before anything trips or fails visibly.
Bearing Failure DC motor bearings fail the same way AC motor bearings do — contamination, lubrication failure, misalignment load. They announce themselves with noise and heat long before they seize. This checklist makes sure someone is listening.
Loose or Corroded Electrical Connections High-resistance connections at the terminal box generate heat, increase current draw, and degrade insulation — all before they trip a fault or show visible damage during a casual walk-by.
Drive Connection Wear Loose couplings and worn keyways transmit misalignment forces directly into the motor shaft and bearings. It starts as vibration. It ends as a bearing event.
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