What does motor T (A) mean on a Kaeser Sigma Control?
Short answer: Drive motor too hot. If your Kaeser Sigma Control (original) is showing motor T (A), 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 drive motor temperature (sensed by the PTC sensor and trip) is too high and the package shut down; "motor T" also appears as a warning when the motor is very hot but still running.
Which machines show this?
first-generation Kaeser rotary screw compressors fitted with the original Sigma Control — the green-keypad, text-display controller Kaeser introduced around the turn of the 2000s on its direct-drive screw packages. This controller shows faults as short lower-case text messages with a severity letter: (A) for an alarm that shuts the machine down, (W) for a warning it keeps running through — so 'ADT (A)' is an airend-temperature shutdown while 'separator dp (W)' is a clogging separator flagged early. Alarms are acknowledged with the reset key after the cause is fixed. Practical tip: these machines also enforce a minimum start temperature of +3 °C, so a winter no-start in an unheated room is often the controller doing its job, not a fault.
What causes it?
- Motor cooling starved by poor ventilation
- Dirt buildup on the motor
- PTC sensor and trip doing their job on a genuinely hot motor
Can you fix it yourself?
Often, yes — ventilation and a clean motor fix the common cases; let it cool, reset, and monitor.
Step by step — what to try, in order:
- Ensure sufficient ventilation around the machine.
- Clean the motor if it is dirty.
- Let it cool, then reset and monitor.
When do you need a technician — and why?
Persistent overheating is a case for Kaeser service — options like a cooling air discharge fan, or motor checks that need more than a visual inspection.
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 motor T (A) mean on a Kaeser Sigma Control (original)?
Drive motor too hot. The drive motor temperature (sensed by the PTC sensor and trip) is too high and the package shut down; "motor T" also appears as a warning when the motor is very hot but still running.
Can I fix motor T (A) on a Kaeser Sigma Control (original) myself?
Often, yes — ventilation and a clean motor fix the common cases; let it cool, reset, and monitor.
When does motor T (A) on a Kaeser Sigma Control (original) need a technician?
Persistent overheating is a case for Kaeser service — options like a cooling air discharge fan, or motor checks that need more than a visual inspection. If overheating persists, contact Kaeser service about fitting a cooling air discharge fan or checking the motor.
Verified against service documentation: Kaeser Sigma Control (original) documentation for motor T (A) (airsolcan.com)