Why is the VFD running hot on my Sullair compressor?
Short answer: Variable frequency drive running hot. If your Sullair Touch Screen (STS) is showing VFD Overtemp, 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?
Warning that the variable frequency drive is operating near its design temperature limit. Left uncorrected it can escalate to a shutdown.
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?
- Ventilation around the drive cabinet inadequate
- Cabinet vents and filters blocked by dust
- Left alone, escalates from warning to shutdown
Can you fix it yourself?
Partly — improving room ventilation and an external check of cabinet vents is fair; the cleaning that matters happens inside the cabinet.
Step by step — what to try, in order:
- Ensure adequate ventilation around the compressor and drive cabinet
- Check that cabinet vents and filters are not blocked by dust (external inspection only)
- Schedule a cleaning before a high-temperature fault forces a shutdown
When do you need a technician — and why?
The drive cabinet contains high-voltage components with capacitors that hold charge after power-off — internal cleaning and inspection is service-only.
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 VFD Overtemp mean on a Sullair Touch Screen (STS)?
Variable frequency drive running hot. Warning that the variable frequency drive is operating near its design temperature limit. Left uncorrected it can escalate to a shutdown.
Can I fix VFD Overtemp on a Sullair Touch Screen (STS) myself?
Partly — improving room ventilation and an external check of cabinet vents is fair; the cleaning that matters happens inside the cabinet.
When does VFD Overtemp on a Sullair Touch Screen (STS) need a technician?
The drive cabinet contains high-voltage components with capacitors that hold charge after power-off — internal cleaning and inspection is service-only. Call service to clean and inspect the drive internals — the drive cabinet contains high-voltage components.
Verified against service documentation: Sullair Touch Screen (STS) documentation for VFD Overtemp (sullair.com)