How do I reset the emergency stop on a Kaeser compressor?
Short answer: Emergency stop button pressed. If your Kaeser Sigma Control (original) is showing emergency stop (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 emergency stop button was pressed and is latched; the package is shut down until it is released and the alarm reset.
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?
- The emergency stop button is pressed and latched
- The stop circuit faulty if the alarm survives releasing the button
Can you fix it yourself?
Yes — verify the hazard is cleared, unlatch the pushbutton, and press the reset key. That is the whole procedure.
Step by step — what to try, in order:
- Verify the hazard that prompted the stop is cleared.
- Unlatch the pushbutton.
- Press the reset key on the controller to acknowledge the alarm.
When do you need a technician — and why?
An alarm that will not clear with the button released means the stop circuit needs service — a safety circuit is never something to bridge or bypass.
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 emergency stop (A) mean on a Kaeser Sigma Control (original)?
Emergency stop button pressed. The emergency stop button was pressed and is latched; the package is shut down until it is released and the alarm reset.
Can I fix emergency stop (A) on a Kaeser Sigma Control (original) myself?
Yes — verify the hazard is cleared, unlatch the pushbutton, and press the reset key. That is the whole procedure.
When does emergency stop (A) on a Kaeser Sigma Control (original) need a technician?
An alarm that will not clear with the button released means the stop circuit needs service — a safety circuit is never something to bridge or bypass. If the alarm will not clear with the button released, call service to check the stop circuit.
Verified against service documentation: Kaeser Sigma Control (original) documentation for emergency stop (A) (airsolcan.com)