Is My Electric Motor Trending Bad? Look for These 5 Warning Signs

It’s music to your ears as you walk the floor at your facility: the steady hum of motors keeping production running. But what happens when that hum changes? When vibration increases just slightly? When a bearing starts making noise that's not quite right?

Motors don't just fail overnight. They give you warnings. The question is: are you reading the signs?

At Independent Electric, we've spent over 100 years helping Midwest manufacturers avoid catastrophic motor failures. And here's what we've learned: the difference between a minor repair and a full rewind often comes down to catching warning signs early. Let's walk through the five most common signs that your motor is trending bad.

Warning Sign #1: Changes in Sound

Your ears are great diagnostic tools. When a motor's sound changes, something mechanical or electrical has shifted.

Electrical issues create high-pitched sounds—ringing, humming that changes pitch, or crackling and arcing. Mechanical problems sound different: knocking, grinding, or that rough metal-to-metal scraping that reminds you of a failing wheel bearing in your car.

Here's a pro tip from our service team: compare your suspect motor to a similar one nearby. If one sounds louder, rougher, or has different tones than a comparable motor, that's a warning sign that something's wrong.

The type of noise matters because it can give you an insight into what's failing. Most motors fail because of mechanical issues. But when mechanical problems get bad enough—when a bearing completely fails and the rotor drops—it starts dragging on the stator iron and blows up the winding. So, you might have started with a mechanical problem, but it can become an electrical catastrophe if left unchecked. 

Warning Sign #2: Increased Vibration

Vibration signals what's happening inside your motor. When vibration increases or changes character, pay attention.

You might notice excessive rocking or shaking. You might feel vibration that's stronger than it used to be. In severe cases, you can actually see the motor vibrating without touching it. 

Vibration usually points to one of three problems: bearing wear (which accounts for about 60% of motor failures), misalignment between the motor and driven equipment, or imbalance in the rotor or driven equipment.

The good news: vibration problems are detectable through testing long before you can feel them by hand. Vibration analysis measures bearing sounds in decibels and compares them to thresholds that predict failure. Healthy bearings run in the 0-10 decibel range. When readings hit 14 decibels or higher, that bearing is starting to fail. By the time you can hear it without equipment, it's already in bad shape.

Warning Sign #3: Temperature Changes

Heat indicates friction, and friction isn’t good for electric motors. Temperature warnings come in several forms.

• What you can see: Paint discoloration around bearing housings tells you that the bearing has been running hot. Visible heat shimmer when the motor is running suggests temperatures beyond normal operating range. If the motor is unusually hot to the touch compared to similar equipment in your facility, then it’s time to investigate.

• What monitoring systems tell you: Larger motors often have RTDs (resistance temperature detectors) installed in windings and on bearings. These feed into your PLC system with preset thresholds. When the temperature crosses into the alarm zone, the system warns you. If it climbs into the danger zone, it shuts the motor down to prevent damage to the winding.

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Temperature and lubrication have an interesting relationship. When bearing temperature rises, you might add grease to cool it down. But here's the catch: too much grease can actually cause the temperature to spike. If you're adding lubrication and seeing temperature increase instead of decrease, you may need to shut down, let it cool, and start over.

Warning Sign #4: Performance Drop

Sometimes the motor keeps running, but the application tells you something's wrong. Watch for these performance indicators:

• The motor struggles to reach full speed under normal load conditions. 

• Power output drops even though you know the load hasn't changed. 

• Equipment starts underperforming: pumps move less fluid, fans move less air, and conveyors run slower than usual.

Electric motors are designed to maintain RPM even as problems develop, but they may lose power under load. If your process isn't performing as expected and the motor is the driver, investigate the motor health.

Your electrical protection systems also know something's wrong. Starter trips become more frequent. Thermal overload protection engages even though operating conditions seem normal. Circuit breakers trip repeatedly without an obvious cause. These aren't nuisance trips—they're your electrical system telling you the motor is drawing too much current or generating too much heat.

Warning Sign #5: Visual Damage and Leakage

Some problems announce themselves visually. Check for oil or grease leaking from bearing seals. When seals fail, lubrication escapes, and contamination can enter. Look for moisture accumulation around the motor housing, which is especially problematic for electrical components. Watch for debris buildup that can block cooling or indicate environmental contamination.

Some visual signs demand immediate attention: melted or damaged wiring around connection points, insulation melting off lead wires (which exposes conductors and creates short circuit risks), and discolored connection points indicating arcing or excessive current draw. And if you see smoke, that motor needs more than a quick fix!

Understanding the Progression

Here's how motor problems typically escalate:

1. Early Warning (Minor Repair Territory): You notice slight noise changes, minor vibration increases in monitoring data, or small temperature variations in trending. This is when a bearing replacement or minor adjustment prevents bigger problems.

2. Trending Bad (Still Preventable): Indicators worsen consistently over weeks or months. Warning signs become visible or audible without specialized equipment. You're still in control of timing, but the window is closing.

3. Critical (Major Repair Needed): Abnormal noise is apparent to anyone nearby. Excessive vibration is visible or easily felt. Significant heat beyond normal operating temperature affects performance. You need to plan for repair during your next shutdown window.

4. Catastrophic (Complete Failure): Smoke, burning smell, won't start or stay running. This is the emergency situation that early detection helps you avoid.

The economics tell the story: a $1,000 bearing replacement beats a $10,000 rewind, which beats $100,000 in lost production. Early detection transforms the economics completely.

What to Do When You Spot Warning Signs

Don't ignore what your motors are telling you. Start by documenting what you're observing: note sounds, vibration characteristics, temperature changes, or performance issues. Compare the suspect motor to similar equipment in your facility. Check for obvious mechanical issues like loose mounting or visible damage. Review maintenance history to see if this is a recurring issue.

Then bring in professional assessment. At Independent Electric, we offer a free 24-hour turnaround on initial evaluations. We'll tell you if the motor is a good candidate for repair or if replacement makes more economic sense. PdMA testing reveals electrical health, while vibration analysis assesses mechanical condition. For critical equipment, route-based monitoring at regular intervals (often quarterly) catches trends over time and forecasts when maintenance will be needed.

The testing advantage: baseline data gives you comparison points. When test results start degrading, we can forecast when that motor might fail. Instead of guessing or waiting for catastrophic failure, you schedule repair when it fits your production schedule.

The Bottom Line

Motors talk to you constantly through sound, vibration, temperature, and performance. Early detection changes everything. It transforms expensive emergency rewinds into manageable bearing replacements. It turns production-stopping catastrophic failures into planned maintenance during scheduled downtime.