Generac Generator Running but House Has No Power

Quick Checks

1. Check the Generator Main Breaker

Look for the generator's:

• MLCB
• Main line circuit breaker
• Generator disconnect

It must be:

ON / CLOSED

for generator power to reach the transfer switch and house.

If it is OFF, do not blindly switch it on until you understand why it is off.

It may have been intentionally opened for:

• Maintenance
• Troubleshooting
• Electrical work

2. Check the Controller

Confirm:

• Generator is actually running normally
• No red alarm
• No active code
• Unit is in the expected outage state

An engine can run while a separate electrical or transfer problem prevents power delivery.

See Generac error codes →

3. Automatic Transfer Switch Did Not Transfer

The ATS is what moves the house from utility power to generator power.

If the engine starts but the ATS does not transfer, the house can remain dark.

Current Generac control wiring includes transfer-related circuits such as:

• Wire 194 supplying 12VDC to transfer-switch control
• Wire 23 used by the generator controller to command the transfer relay

If those circuits are not functioning correctly, transfer may fail.

This is service-level electrical diagnosis.

Read Generac transfer-switch troubleshooting →

4. Check Whether Utility Is Actually Out

Generac systems use utility-sensing wires such as:

N1 / N2

to detect utility loss and restoration.

If utility sensing is incorrect, the system may behave unexpectedly.

A generator that starts at the wrong time or fails to transfer correctly can involve:

• Sensing
• Fuses
• Control wiring

Do not probe transfer-switch live circuits unless qualified.

5. Some House Circuits Have Power, Others Do Not

If only part of the house is dead, inspect:

• Main electrical panel breakers
• Load-management modules
• Selected-circuit transfer design
• Tripped branch breakers

A 10kW essential-circuit system may never have been designed to power every panel circuit.

6. Load Management Can Intentionally Keep Loads Off

Generac load-management systems can shed large loads.

That means items such as:

• AC
• Water heater
• Pool equipment

may remain off even while the generator is powering the house.

This is not necessarily a fault.

7. Generator Runs but 240V Loads Do Not Work

If lights/outlets work but major 240V equipment does not, possible areas include:

• Breaker/panel condition
• Transfer-switch contact issue
• Generator output issue
• Load-management state

This is not a safe DIY voltage-tracing job for most homeowners.

Use a qualified electrician or Generac dealer.

8. Generator Runs but No Power After Maintenance

Check whether the generator MLCB was left OFF after service.

Generac maintenance procedures often involve opening the generator breaker.

The technician can finish the engine work, return the controller to AUTO and still leave the output breaker open.

That creates exactly this symptom:

generator starts, house stays dark.

9. Generator Runs but No Power After Battery Replacement

Again check:

• AUTO mode
• Generator MLCB
• Active alarms
• ATS state

Battery service itself does not normally require permanent changes to the transfer position.

10. Should You Manually Operate the Transfer Switch?

Generac provides manual transfer procedures for certain service-entrance-rated switches with a dead-front design.

But Generac also warns that transfer switches can contain hazardous live voltage.

Do not open a transfer switch or operate exposed internal mechanisms unless the exact switch/manual permits it and you are qualified to do so.

For most homeowners:

call the dealer/electrician.

When to Call Service

Call when:

• MLCB is ON but house has no power
• ATS does not transfer
• Only one leg of power appears present
• Transfer wiring is suspected
• Breaker trips again
• Generator output is uncertain
• You smell burning or see damage