How to Determine if a Motor Has Water Ingress?
3 Answers
When a motor has water ingress, the insulation resistance between its components decreases. Using the high-resistance range of a multimeter, it is convenient to measure whether the motor has water ingress. The phase wires are insulated from the motor hub and end cover. After water ingress, resistance will develop between them, which can also be measured using the resistance range of a multimeter.
Determining whether a motor has been flooded is actually not difficult, as I often encounter customers asking about this. The most intuitive method is to check for water stains or rust spots on the motor casing, especially around the sealing ring, which is particularly prone to water seepage. Once water enters, the motor will produce a noticeable 'buzzing' abnormal noise during operation, feeling like it's rotating with water inside, and the speed will be unstable or even suddenly stop. When I disassemble it for inspection, finding patina or burnt spots on the winding coils can basically confirm the diagnosis. This situation often occurs after driving through water, and it is recommended to immediately disconnect the power to avoid short circuits. You can wipe the interior with a dry cloth and let it dry, but in severe cases, the sealing ring or the entire stator assembly may need to be replaced. Regularly checking the waterproof strips on the chassis is crucial, especially before the rainy season.
After the last heavy rain, my electric vehicle's motor developed a problem with classic symptoms: first, it lost power during acceleration and struggled even on small slopes. After parking, I noticed a strange smell like a mix of rust and something burnt. Upon opening the motor cover, I found water droplet marks on the inner walls. The mechanic taught me a practical trick—using a multimeter to test the insulation resistance. If the reading is below 0.5 megaohms, there's a high chance of water ingress. It turned out to be caused by aging rubber seals on the shaft. He advised that after driving through water, don't turn off the engine immediately; keep it running for a few minutes to let the heat evaporate any moisture. Also, never point a high-pressure car wash spray directly at the motor.
