Why did my Sullair compressor trip on main motor overload?
Short answer: Main drive motor overload trip. If your Sullair Touch Screen (STS) is showing Main 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 main motor overload relay has tripped, shutting the compressor down. Common causes are low line voltage, discharge pressure set above the compressor's limit, or a misconfigured machine.
Which machines show this?
current-generation Sullair stationary rotary screw compressors — the LS-series and related packages built from the late 2010s onward — fitted with the 10-inch Sullair Touch Screen (STS) controller. The STS spells out problems as plain-English named faults and warnings ('High Temperature 1', 'Failed to Unload', 'Replace I/O Battery') rather than bare code numbers, and pairs them with live readings and a Recommended Service screen that tracks filter and separator hours. Warnings keep the machine running; faults shut it down until reset. Practical tip: before clearing anything, photograph the fault screen and the Recommended Service page — the service-hour counters usually point straight at the consumable that caused the trip.
What causes it?
- Low line voltage — sometimes sag caused by other equipment on the same supply
- Discharge pressure setpoint set above the compressor's limit
- A misconfigured machine
Can you fix it yourself?
Partly — let the overload cool, reset per the manual, and verify the pressure setpoint against the rating. A second trip ends the DIY phase.
Step by step — what to try, in order:
- Wait for the overload element to cool, then reset per the operator manual
- Confirm the load/target pressure setpoint is not set above the machine's rated pressure
- Check whether other equipment on the same supply is causing voltage sag; if line voltage is low, consult the power company
When do you need a technician — and why?
Motor amps, starter contacts, and wiring have to be checked with proper instruments inside a high-voltage enclosure — electrician or Sullair service work.
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 Main Motor Overload mean on a Sullair Touch Screen (STS)?
Main drive motor overload trip. The main motor overload relay has tripped, shutting the compressor down. Common causes are low line voltage, discharge pressure set above the compressor's limit, or a misconfigured machine.
Can I fix Main Motor Overload on a Sullair Touch Screen (STS) myself?
Partly — let the overload cool, reset per the manual, and verify the pressure setpoint against the rating. A second trip ends the DIY phase.
When does Main Motor Overload on a Sullair Touch Screen (STS) need a technician?
Motor amps, starter contacts, and wiring have to be checked with proper instruments inside a high-voltage enclosure — electrician or Sullair service work. Call an electrician or Sullair service if the overload trips again — motor amps, starter contacts, and wiring need to be checked with proper instruments.
Verified against service documentation: Sullair Touch Screen (STS) documentation for Main Motor Overload (sullair.com)