What does Kaeser warning 0004 W (oil separator clogging) mean?
Short answer: Oil separator differential pressure rising (warning). If your Kaeser Sigma Control 2 is showing 0004 W — Oil separator Δp ↑, 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?
Increased differential pressure across the oil separator cartridge — it is clogging but the machine still runs. Replacement of the cartridge is the documented remedy.
Which machines show this?
the wide range of current-generation Kaeser rotary screw compressors — ASD, BSD, CSD, DSD, ESD and related series — built since roughly 2011 with the Sigma Control 2, the industrial-PC controller with a text display and RFID access. It reports faults as a four-digit number plus a letter: 'A' messages are alarms that shut the machine down, 'W' messages are warnings or service reminders it keeps running through, with arrows marking whether the value went over or under its limit — so 0015 A is the airend-overheat shutdown while 0013 W just asks for an air filter. Practical tip: the same subsystem often has a W and an A code (0004 W before 0022 A on the separator); acting on the W message is how you avoid the A shutdown.
What causes it?
- Separator cartridge clogging progressively — the warning stage before the 0022 A shutdown
- Cartridge approaching end of life
Can you fix it yourself?
Yes, as planning — order the genuine cartridge now and schedule the swap during downtime, before it becomes a shutdown. The swap itself needs a trained pair of hands.
Step by step — what to try, in order:
- Order a genuine replacement oil separator cartridge now, before it becomes a shutdown alarm (0022 A).
- Plan the swap during scheduled downtime.
When do you need a technician — and why?
The change means opening the pressurized separator tank after full depressurization — trained-technician work unless your team is qualified on this exact procedure.
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 0004 W — Oil separator Δp ↑ mean on a Kaeser Sigma Control 2?
Oil separator differential pressure rising (warning). Increased differential pressure across the oil separator cartridge — it is clogging but the machine still runs. Replacement of the cartridge is the documented remedy.
Can I fix 0004 W — Oil separator Δp ↑ on a Kaeser Sigma Control 2 myself?
Yes, as planning — order the genuine cartridge now and schedule the swap during downtime, before it becomes a shutdown. The swap itself needs a trained pair of hands.
When does 0004 W — Oil separator Δp ↑ on a Kaeser Sigma Control 2 need a technician?
The change means opening the pressurized separator tank after full depressurization — trained-technician work unless your team is qualified on this exact procedure. Have Kaeser service or a trained technician perform the cartridge change if you are not trained on depressurizing the unit.
Verified against service documentation: Kaeser Sigma Control 2 documentation for 0004 W — Oil separator Δp ↑ (airsolcan.com)