Hey there! I've been dealing with this exact frustrating issue - when your servo motor gets hot but doesn't throw any clear error codes. It's like the motor is trying to tell you something's wrong, but it's speaking in riddles! Based on my research and experience, here's the most effective diagnostic approach:

First, start with thermal imaging to create a heat map of your motor during operation. This helps you identify hot spots that might indicate bearing issues, winding problems, or cooling system failures. Look for temperature patterns that correlate with specific operations or load conditions.

Next, layer in vibration analysis. This is crucial because vibration issues often create heat through friction. Use vibration analyzers to detect bearing wear, misalignment, or mechanical imbalances that might not show up on thermal imaging alone. The research shows vibration analysis is actually more effective than thermography for detecting misalignment problems.

Then add power quality monitoring. This is where you catch those sneaky electrical issues - voltage spikes, harmonics, or inconsistent power supply that can cause intermittent overheating. Faulty wiring or electrical imbalances are common culprits that thermal and vibration analysis might miss.

The key is to run all three diagnostics simultaneously during the same operational cycles. This integrated approach lets you correlate data - for example, does a vibration spike coincide with a temperature increase and a power quality anomaly? That correlation gives you the most reliable root cause identification.

Remember to check for blocked vents, inadequate ventilation, and environmental factors too. Many technicians use this combined approach with oscilloscopes, thermal cameras, vibration analyzers, and multimeters to troubleshoot these tricky intermittent issues effectively.