What is the Generac 22kW Generator Error Code 1505?

If you are receiving a Generac 22kW Generator Error Code 1505, it means the generator tried to start but didn’t detect engine RPM. This “RPM loss during cranking” error prevents your generator from running—and often shows up right when you need backup power most.

At Best Care Home Services, we help Memphis homeowners troubleshoot and fix common Generac generator problems like error code 1505. Here’s how to diagnose the issue, what causes it, and when to call a certified technician.

What Does the Generac 22kW Generator Error Code 1505 mean?

Error code 1505 is an RPM sense loss alarm. It means your Generac generator’s controller didn’t detect the engine turning fast enough during startup. This causes an automatic shutdown to protect the unit from damage.

In most cases, this issue is tied to one of the following:

• Weak or failing battery
• Faulty starter relay
• Damaged wiring (especially Wire 18)
• Failed starter motor or solenoid
• RPM sensor or ignition coil issue
• Control board malfunction

Common Causes of the Generac 22kW Generator Error Code 1505

1. Weak or Dead Battery

Even if your battery shows normal voltage when idle, it might not deliver enough power under load. During cranking, if voltage drops below 10 volts, the starter may not engage fully—causing error 1505.

Solution: Load-test the battery. Replace it if it drops below 10 volts when starting.

2. Starter Relay Failure

The starter relay sends power from the controller to the starter motor. If it’s damaged or the contacts are corroded, the motor won’t crank.

Solution: Inspect or swap the starter relay with a known-good one. Check for loose pins or burned connectors.

3. Wiring Problems (Especially Wire 18)

Generac standby generators rely on clean, secure wiring connections—especially Wire 18, which carries the RPM signal to the controller. Corrosion, loose connections, or rodent damage can cause signal loss.

Solution: Inspect the wiring harness and connector pins. Clean, tighten, or replace as needed.

4. Failed Starter Motor or Solenoid

If the starter motor is slow, weak, or not engaging at all, it can prevent the engine from reaching its required RPM during cranking.

Solution: Test the starter solenoid and motor for continuity and power delivery. Replace if worn or failing.

5. RPM Sensor or Ignition Coil Issue

Some Generac models rely on the ignition coil or flywheel sensor to report RPM back to the control board. If no signal is received, the unit shuts down.

Solution: Test for continuity and voltage on the sensor wire. Inspect the coil and replace if needed.

6. Controller or Circuit Board Failure

If all other components check out, the problem may lie within the Evolution controller itself. Faulty circuitry or software issues can lead to false shutdowns.

Solution: Replace or reprogram the controller, ideally with help from a certified Generac technician.

Step-by-Step Troubleshooting for Error Code 1505

1. Test the battery under load, not just at rest.
2. Inspect the starter relay and harness. Clean and re-seat connections.
3. Check the starter motor and make sure 12 volts reaches the solenoid during crank.
4. Trace Wire 18 and verify it’s connected and intact.
5. Clear the code by pressing ENTER twice, then return to AUTO.
6. Try starting the unit manually. If manual start works but auto does not, the issue is likely in the control wiring or relay.

What to Do If Your Generac Generator Still Won’t Start

If your Generac 22kW generator continues to display error code 1505 after basic troubleshooting, it’s time to schedule professional service. A certified technician from Best Care Home Services can:

• Load test and replace the battery if needed
• Diagnose wiring, relay, and starter faults
• Replace the RPM sensor, ignition coil, or starter motor
• Reprogram or replace the controller if necessary

We also provide regular maintenance services to catch these issues before they interrupt power to your home.

Preventing Error Code 1505: Home Generator Maintenance Tips

Many 1505 errors can be avoided with consistent generator maintenance. Here’s what we recommend:

• Run your generator under load once a month
• Replace the battery every 2–3 years
• Keep wiring connections clean and dry
• Schedule annual professional inspections
• Enroll in a ComfortGuard Maintenance Plan from Best Care Home Services for peace of mind

What is the Generac 22kW Generator Error Code 1505?? Best Care Home Services Can Help

Error code 1505 can leave your home without power when you need it most. If your Generac 22kW generator won’t start and keeps showing this fault, don’t wait. The certified experts at Best Care Home Services in Memphis can diagnose and fix the issue fast—so your backup generator is always ready to go.

Call 901-624-1401 to schedule your generator repair today.