ATS ComError Code: Kohler RDC2 Communication Troubleshooting

Understanding the ATS ComError

The ATS ComError is a warning that appears on your Kohler RDC2 controller when the automatic transfer switch interface board stops “talking” to the main generator control system. Think of it like a phone line going dead—the two devices are supposed to be in constant contact, and when that connection breaks, the controller alerts you.

This error is specific to Kohler’s 14RCA, 20RCA, 26RCA, and RCAL series generators equipped with the RDC2 controller. The automatic transfer switch is the device that detects when utility power fails and signals your generator to start and take over the load. If the ATS can’t communicate with the controller, the system can’t coordinate that handoff properly, which is why you get a warning instead of letting it slide silently.

The good news: this is almost always a wiring issue, not a failed component. Most homeowners can diagnose and fix this themselves with basic tools and a little patience.

Why Communication Fails

Several common culprits cause ATS communication errors:

• Loose connectors: Vibration from the generator running, temperature cycling, or just age can loosen the plugs that connect the ATS interface board to the controller.
• Corroded terminals: Moisture in the electrical enclosure can oxidize the metal contacts, blocking the signal.
• Damaged wiring: Rodents, physical damage during maintenance, or UV exposure can crack or sever the communication cable.
• Pinched or crushed cables: If wiring was installed near sharp edges or has been compressed over time, the insulation or conductors inside can fail.
• Wrong or missing connectors: If someone replaced a section of wiring or the interface board, they may have used the wrong connector type or failed to fully seat it.
• Water intrusion: Generators installed outdoors without proper weatherproofing can develop moisture inside the control enclosure.

Diagnostic Checklist

Work through these steps in order. Start with the easiest and cheapest checks first.

1. Power cycle the generator. Turn off the main breaker, wait 30 seconds, and turn it back on. Sometimes a temporary glitch clears itself. If the error returns immediately, move to step 2.
2. Inspect the RDC2 controller display. Note exactly when the error appears (during startup, after running, or constantly). Does it appear every time, or intermittently? This tells you whether it’s a loose connection (intermittent) or a broken wire (constant).
3. Visually inspect the wiring between the ATS interface board and the RDC2 controller. Look for obvious damage: cracks in insulation, exposed copper, pinched cables, or signs of rodent chewing. Trace the cable from one end to the other. Check both the main generator enclosure and any external transfer switch cabinet.
4. Check all connectors for tightness. Locate the plugs where the communication cable connects to both the ATS interface board and the RDC2 controller. Gently try to wiggle each connector. It should not move. If it does, disconnect it fully, inspect the pins or terminals for corrosion (greenish or white buildup), and reconnect firmly until you hear or feel a click.
5. Clean corroded terminals. If you see corrosion on the connector pins, disconnect the cable and use a pencil eraser or fine-grit sandpaper to gently clean the metal surfaces. Reconnect and test.
6. Check for water inside the control enclosure. If your generator is outdoors, look for condensation, water droplets, or a musty smell inside the electrical cabinet. If present, dry the area with a cloth and ensure the enclosure is properly sealed. Check that all cable entry points have weatherproof glands or seals.
7. Verify cable routing. Make sure the communication cable is not routed near sharp edges, hot surfaces, or moving parts. If it’s pinched or rubbing, it may have internal damage even if the insulation looks okay.
8. Test after each fix. After each step, power the generator back on and check whether the error clears. If it does, you’ve found your problem. If not, continue to the next step.

When to Call a Pro

Stop troubleshooting and contact a qualified Kohler service technician if:

• You find a visibly damaged or severed communication cable and don’t feel confident replacing it yourself.
• The connectors are corroded but cleaning doesn’t resolve the error.
• The error persists after you’ve checked all visible wiring and connectors.
• You suspect water damage inside the control enclosure—this requires professional drying and may indicate a deeper weatherproofing issue.
• The ATS interface board itself appears damaged (cracked circuit board, burned components, or loose internal parts).
• You’re uncomfortable working inside the generator’s electrical enclosure or near high-voltage components.

A technician has diagnostic tools to test the actual signal passing through the communication line and can confirm whether the problem is wiring, a connector, or the interface board itself.

Parts You May Need

• Replacement communication cable (if damaged beyond repair)
• Connector plugs or terminals (if corroded or broken)
• Weatherproof cable glands or seals (if water intrusion is the cause)
• Electrical contact cleaner (for corrosion removal)
• Dielectric grease (to protect terminals after cleaning)

Prevention Tips

Once you’ve resolved the ATS ComError, keep it from happening again:

• Keep the enclosure sealed: Ensure all cable entry points are properly sealed with weatherproof glands, especially on outdoor units.
• Inspect wiring annually: Before winter or at the start of storm season, visually check the communication cable for damage.
• Avoid moisture buildup: If your generator is in a damp location, consider installing a small desiccant pack or heater inside the control enclosure.
• Protect from rodents: Use wire mesh or hardware cloth around cable entry points if rodent damage is a recurring issue in your area.
• Secure cables properly: Use cable clips or conduit to keep wiring away from sharp edges and moving parts.

Frequently Asked Questions

Can I run my generator if the ATS ComError is showing?

The generator will still run and produce power, but the automatic transfer switch may not function correctly. In a power outage, the ATS might not detect the loss or signal the generator to start and switch loads automatically. You should resolve the communication error before relying on automatic operation. Manual operation is still possible if needed in an emergency.

Why does the error come and go?

An intermittent ATS ComError almost always means a loose connector or a damaged wire that makes and breaks contact as the generator vibrates or as temperature changes cause expansion and contraction. This is actually helpful—it narrows your search to the physical connection points rather than a complete break.

Is the ATS interface board expensive to replace?

Interface boards vary in cost depending on your generator model, but most are less expensive than a service call. However, before replacing the board, confirm with a technician that the problem is actually the board and not the wiring. Replacing a $50 cable is far cheaper than replacing a $300 board unnecessarily.

What’s the difference between ATS ComError and other controller warnings?

ATS ComError is specific to the communication link between the transfer switch and the controller. Other warnings might indicate low oil, high temperature, battery issues, or fuel problems—all of which have different causes and fixes. Always read the full error code and description on your RDC2 display to understand what system is affected.

Disclaimer: This article provides general information for educational purposes. Always consult your Kohler generator’s owner’s manual and follow the manufacturer’s specific instructions for your model before performing any maintenance or repairs. If you are unsure about any procedure, contact a qualified service technician. Improper work on electrical systems can be dangerous.

Source: Information adapted from official manufacturer documentation (reference). Always consult your generator owner’s manual for model-specific procedures.