What does Aux Motor Overload mean on a Sullair WS controller?
Short answer: Auxiliary motor (fan/pump) overload trip. If your Sullair WS Controller is showing Aux Motor Overload, the controller has logged a specific, documented condition. This page covers what it means, what causes it, what you can safely fix yourself, and when — and why — it takes a technician.
What exactly is the machine telling you?
The auxiliary motor overload relay tripped on the cooling fan, fluid pump, or other auxiliary motor.
Which machines show this?
Sullair's mid-range stationary rotary screws fitted with the WS controller — a text-display unit found on many shop and light-industrial packages from the 2010s. The WS names its faults in plain English (High Temperature, Separator dP High, Aux Motor Overload, Power Interruption) and uses staged temperature protection: a warning at 225 °F, a time-delayed fault at 235 °F, and an immediate trip at 255 °F. Faults are reset from the STOP key after the cause is corrected and the unit has cooled. Practical tip: if the auto-restart timer is configured, the machine can start by itself after a power interruption — make sure nobody is working near it before you walk away from a Power Interruption message.
What causes it?
- Cooling fan or fluid pump motor drawing excess current
- Fan blocked by debris (check with power locked out)
- Building voltage sagging — dimming lights are the tell
Can you fix it yourself?
Sometimes — cool-down, a locked-out check that the fan spins freely, and one reset. Repeated trips end the DIY phase.
Step by step — what to try, in order:
- Allow the overload element to cool before resetting
- Check that the cooling fan spins freely and is not blocked by debris (power locked out)
- If lights dim or voltage sags in the building, have the utility supply checked
When do you need a technician — and why?
Verifying motor amps, starter contacts, and connections is instrument work in a live-capable enclosure — electrician or service tech.
If it does come to a service call and you're in Nashville, TN or Birmingham, AL, we maintain independently compiled lists of local companies that service industrial air compressors — real businesses with verified contact information, none of whom paid to be listed.
Related questions
What does Aux Motor Overload mean on a Sullair WS Controller?
Auxiliary motor (fan/pump) overload trip. The auxiliary motor overload relay tripped on the cooling fan, fluid pump, or other auxiliary motor.
Can I fix Aux Motor Overload on a Sullair WS Controller myself?
Sometimes — cool-down, a locked-out check that the fan spins freely, and one reset. Repeated trips end the DIY phase.
When does Aux Motor Overload on a Sullair WS Controller need a technician?
Verifying motor amps, starter contacts, and connections is instrument work in a live-capable enclosure — electrician or service tech. Call an electrician or service tech to verify motor amps, starter contacts, and connections if it trips again.
Verified against service documentation: Sullair WS Controller documentation for Aux Motor Overload (best-aire.com)