If your Kaeser compressor just threw an alarm code and shut down, you're probably not browsing for fun. You need to know what that code means, and more importantly, can you fix it now, or do you need a part shipped overnight? I've been on both sides of that desk. I'll walk through the most common fault codes, what they actually mean on the shop floor, and the fastest way to get back online.
What are the most common Kaeser compressor alarm codes?
The ones that stop you cold are usually tied to motor temperature, pressure loss, or a service interval hit. In my experience, the codes you'll see most often are E1, E10, E20, and E30. But the specific code depends on your controller. A CS125 and a BSD 75 will throw different codes for the same basic issue.
Honestly, the most frequent call I get is for a motor over-temperature shutdown. That's not always a bad motor. Sometimes it's dirty coolers, or a fan that gave up. Let's look at the major ones.
Kaeser Compressor Fault Codes List (Common)
The actual fault code displayed depends heavily on the controller series (Sigma Control 2 vs. older units). This is based on what I see most often in the field. I should add that if your panel is showing a code not listed here, the manual is your first stop. But these are the usual suspects.
- Motor Over-Temperature (E1 or similar): The motor thermal switch tripped. Check the motor cooling fan, the ambient temperature, and if the unit is cycling too frequently. In March 2024, a client's compressor was showing this every 20 minutes. Turned out a plastic bag had blocked the air intake.
- Emergency Stop / Safety Circuit (E10 or similar): The E-stop button is pressed, or a door switch is open. Check all the mushroom buttons on the unit and any remote E-stops. It sounds basic, but we once spent an hour troubleshooting a code that was just a depressed E-stop from the night before.
- High Temperature (E20 or similar): The discharge air or fluid temperature is too high. This is a classic symptom of a failing cooler, a restricted oil filter, or low fluid level. A dirty cooler is the most common non-parts fix. I've cleaned coils that looked like they were wearing a fur coat.
- Motor Overload (E30 or similar): The motor drew too many amps. Check the overload relay setting, the incoming voltage, and for a mechanical bind in the airend. A bad bearing in the airend will pull high amps before it seizes.
How do I look up a Kaeser compressor fault code without the manual?
You're on the clock, and the manual is in a drawer somewhere. I get it. Here's what I do.
First, look at the controller model. It's usually printed on the front. A Sigma Control 2 will often show a code like 'Motor Overload' in plain text on the display. Older controllers use numeric codes. If you have a numeric code you can't find, there are a few landing pages online. (Honestly, I've saved the Kaeser service portal page to my phone's home screen—it's that useful). Actually, the best trick I've found is to search for the controller model and the code number. Like 'Sigma Control 2 E20' instead of just the compressor model.
One thing: if you're seeing a code like 'Low Pressure' or 'Service Due', that's usually less urgent. A service due won't stop the compressor. Low pressure might be a bad sensor or a real air leak downstream. But if the code says 'Emergency Stop' or 'Motor Overload', you have a problem that needs a physical fix before you can reset it.
My Kaeser compressor says 'E1' or 'Motor Over-Temp'. What now?
This is the code that makes maintenance guys sweat. But don't panic and buy a motor. The surprise isn't usually the motor itself—it's the simple things that cause the heat.
Here's a checklist I run through in 30 minutes or less:
- Check the coolers. Are the oil cooler and aftercooler fins clogged with dust, oil, or debris? Clean them with a stiff brush or compressed air (from inside out, if you can). I've seen a 10-minute cooler cleaning drop the discharge temperature by 20 degrees.
- Check the fan. Is the cooling fan running? Is it spinning the right direction? A bad fan motor or a failed capacitor will kill your cooling.
- Check the oil level. Low oil means less cooling and lubrication. Top it off to the sight glass. Use the correct Kaeser fluid. Don't mix fluids.
- Check the ambient temperature. If the compressor room is 110°F, the compressor will struggle. Improving ventilation might cost a lot less than a new compressor.
The most frustrating part of this code: you can reset it, and it might run fine for a while. But if you don't fix the root cause, it will come back. Probably at the worst possible time.
What does a 'High Pressure' or 'E20' fault code mean?
This code usually triggers when the discharge pressure is too high, or the system pressure has hit an unsafe limit. In my role coordinating emergency service calls, this code often points to a blockage or a valve failure.
First, check the minimum pressure valve (MPV). If it's stuck partially closed, it will force the compressor to build pressure against a restriction. You can test this by monitoring the sump pressure versus the discharge pressure. They should be very close on a Kaeser. A big delta means a bad MPV.
Second, check the oil separator. A clogged separator, or one that's collapsing, creates high pressure differential. When I had a client's BSD 75 throwing this code every shift, it wasn't the separator itself—it was a dirty coalescing filter downstream. Replaced the filter, and the problem vanished.
Third: verify your pressure switch settings. If someone has changed the pressure band to be too tight, or the setpoint is too high for the system, the compressor won't unload properly. I once had a facility where the pressure switch was set at 125 psi, but the compressor's max was 130 psi. It was riding the safety valve constantly.
Can I clear a fault code on a Kaeser compressor, or do I need a technician?
For many alarm codes, you can clear them yourself. The procedure is usually simple: press the Stop button, wait for the display to go blank, then press Start. If the fault condition is gone, the compressor will restart.
But—and this is a big but—you should never just clear a fault code without investigating the cause. An active code like 'Motor Overload' is a warning. If you clear it and start the compressor, you could damage the airend or the motor. I've seen a facility burn out a $6,000 motor because they cleared the 'High Temp' code five times without cleaning the cooler.
After clearing a code, stay with the machine for the first 10 minutes. Listen for unusual noises, watch the display for a re-occurring code, and check the temperature ramp-up. If a code comes back within an hour, you need to find the real problem. That's when you call a technician, or order a replacement part like a thermal switch or a fan motor.
For code 'Service Due' or 'Oil Change', you can clear those via the service menu. But actually, you shouldn't clear those—you should schedule the service. I should add that ignoring service intervals is the number one cause of unexpected breakdowns I see. The machine tells you it needs help, and people just hit 'clear'.
Bottom line: a compressor alarm code is your machine talking to you. Listen to it. Fix the problem, not just the symptom. If you're stuck, or you need a part fast, call your local distributor. In my experience, Kaeser's network is pretty good about having common parts like filters and fan motors on hand. But if you're staring at a 'Motor Overload' code on a Friday night, you might be looking at a longer repair cycle. At least, that's been my experience with large-scale emergency orders.
