12 Things Worth Checking Before You Send Equipment Out for Repair
Repair shops regularly receive equipment that didn’t need to be sent in or that arrives without enough information to diagnose efficiently. A few checks before the unit ships can confirm the fault is actually in the component, not in the power supply, wiring, or parameter settings upstream of it. They can also give the repair technician the context needed to get to the root cause faster. Neither outcome requires specialized tools or extended downtime.
1. Check incoming power first
Low voltage, phase loss, or voltage imbalance at the supply is a common cause of faults that look like component failure. A drive faulting on undervoltage may not have a drive problem at all.
2. Verify the fault is repeatable
A fault that happened once and hasn’t returned may be transient, such as a voltage spike, momentary overload, or brief loss of input signal. Intermittent faults warrant monitoring before the unit gets pulled.
3. Check connections and terminals
Loose power terminals, corroded control wiring, and unseated connectors cause a significant share of apparent failures. Torque power terminals and reseat all connectors before declaring the unit failed.
4. Pull the fault log before resetting
Most drives and PLCs store fault codes with the motor current, bus voltage, and output frequency at the time of the trip. That data is the repair shop’s first diagnostic input, and it’s erased by a power cycle on many platforms.
5. Test external wiring for shorts and grounds
A wiring fault on the motor cable produces drive fault codes that look like internal drive failure. Disconnect the motor and test the cable with a megohmmeter before the drive ships.
6. Verify motor condition independently
A failing motor causes VFD faults, starter overloads, and blown fuses. An insulation resistance test and winding resistance balance check confirms whether the fault is in the component being sent or downstream of it.
7. Check fuses, breakers, and contactors
A single blown fuse in a three-fuse disconnect produces phase loss that faults the downstream drive. A contactor with one failed pole does the same. These are five-minute checks that routinely get skipped.
8. Review recent parameter changes
A drive that faulted after a parameter adjustment may be reacting to the parameter, not failing as hardware. Check for recent changes to acceleration ramp, current limit, carrier frequency, or motor nameplate data.
9. Check for obvious environmental causes
A drive that started faulting after a nearby washdown or during a heat wave may be responding to moisture ingress or an ambient temperature that’s crossed its derating threshold, not failing internally.
10. Document the fault symptoms
“Doesn’t work” gives the repair shop nothing useful. “Faults on F7 overcurrent at 45 Hz under load, clears on reset, and returns after approximately 10 minutes of operation” is a diagnostic starting point that saves bench time.
11. Note the operating conditions at failure
Ambient temperature, load conditions, time of day, and whether the fault occurs at startup or during running all help narrow the root cause. Pattern information is often more useful than the fault code.
12. Include the recent maintenance history
A unit that faulted shortly after a bearing replacement, parameter change, or nearby electrical event didn’t fail in a vacuum. That context changes where the repair shop starts looking.
A unit that arrives with complete fault data, documented symptoms, and confirmed external conditions gets diagnosed faster and more accurately than one that arrives with no history. These checks also catch a meaningful percentage of faults that aren’t in the component, saving the round-trip time, repair cost, and additional downtime of shipping something that didn’t need to leave the building.
