Why won't my Kaeser compressor build pressure?
Short answer: No pressure buildup. If your Kaeser Sigma Control (original) is showing no press. buildup (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 package cannot build pressure — package pressure does not rise above 3.5 bar within the preset period. Documented checks include leaks, the inlet valve, and the minimum pressure/check valve (MPCV).
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?
- Leak in the package or nearby piping
- Inlet valve not opening (documented check)
- Minimum pressure/check valve (MPCV) defective
Can you fix it yourself?
Partly — check the package and piping for leaks, and compare the controller's pressure reading against the tank gauge; note any mismatch for the technician.
Step by step — what to try, in order:
- Check the complete package and nearby piping for leaks.
- Compare the controller's internal pressure reading with the gauge on the oil separator tank and note any mismatch for the technician.
When do you need a technician — and why?
If no leak shows, the inlet valve and MPCV need technician diagnosis on the pressurized circuit — the two readings disagreeing also points at a sensor.
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 no press. buildup (A) mean on a Kaeser Sigma Control (original)?
No pressure buildup. The package cannot build pressure — package pressure does not rise above 3.5 bar within the preset period. Documented checks include leaks, the inlet valve, and the minimum pressure/check valve (MPCV).
Can I fix no press. buildup (A) on a Kaeser Sigma Control (original) myself?
Partly — check the package and piping for leaks, and compare the controller's pressure reading against the tank gauge; note any mismatch for the technician.
When does no press. buildup (A) on a Kaeser Sigma Control (original) need a technician?
If no leak shows, the inlet valve and MPCV need technician diagnosis on the pressurized circuit — the two readings disagreeing also points at a sensor. Call Kaeser service if no leak is found — inlet valve and MPCV diagnosis is technician work.
Verified against service documentation: Kaeser Sigma Control (original) documentation for no press. buildup (A) (airsolcan.com)