Why generators show "no ac output voltage": 56 documented causes and brand-specific fixes, compiled across 9 manufacturers.
Field breaker is tripped
3 brands- Cummins/Onan: Reset breaker. Contact a Cummins Dealer or Distributor if voltage build up causes breaker to trip.; Reset breaker. Contact an Onan Dealer or Distributor if voltage build up causes breaker to trip.
- Detector: Reset breaker. Contact an authorized service center if voltage buildup causes breaker to trip.
- Ford: Reset breaker. Contact an authorized service center if voltage buildup causes breaker to trip.; Reset breaker; contact an authorized service center if voltage buildup causes breaker to trip
The line circuit breaker is OFF
2 brands- Cummins/Onan: Find out why the circuit breaker was turned OFF, make sure it is safe to reconnect power, and then throw the circuit breaker ON.
- Orion: Find out why the circuit breaker was turned OFF, make sure it is safe to reconnect power, and then throw the circuit breaker ON.
The line circuit breaker has TRIPPED
2 brands- Cummins/Onan: Shut down the set and service as necessary to clear the short circuit or ground fault that caused tripping, and then RESET the circuit breaker and start the set.
- Orion: Shut down the set and service as necessary to clear the short circuit or ground fault that caused tripping, and then RESET the circuit breaker and start the set.
The line circuit breaker is faulty
2 brands- Cummins/Onan: Shut down the set, make sure the power output lines from the set have been disconnected from all other sources of power, attempt to RESET the circuit breaker and throw it ON and check for electrical continuity across each line contact. Replace the circuit breaker if there is measurable resistance across any contact.
- Orion: Shut down the set, make sure the power output lines from the set have been disconnected from all other sources of power, attempt to RESET the circuit breaker and throw it ON and check for electrical continuity across each line contact. Replace the circuit breaker if there is measurable resistance across any contact.
Field circuit breaker CB21 has TRIPPED
2 brands- Cummins/Onan: RESET the circuit breaker. If it keeps tripping, troubleshoot according to Trouble heading, Field Circuit Breaker Keeps Tripping.
- Orion: RESET the circuit breaker. If it keeps tripping, troubleshoot according to Trouble heading, Field Circuit Breaker Keeps Tripping.
Field circuit breaker CB21 is faulty
2 brands- Cummins/Onan: Shut down the set, attempt to RESET the circuit breaker and disconnect either lead. Replace the circuit breaker if there is measurable resistance across the terminals.
- Orion: Shut down the set, attempt to RESET the circuit breaker and disconnect either lead. Replace the circuit breaker if there is measurable resistance across the terminals.
The field has lost its residual magnetism
2 brands- Cummins/Onan: If reference voltage across TB21-1 & 2 is not 20VAC or more, flash the field according to Servicing the Generator in Section 5.
- Orion: If reference voltage across TB21-1 & 2 is not 20VAC or more, flash the field according to Servicing the Generator in Section 5.
The generator is faulty
2 brands- Cummins/Onan: Disconnect stator leads 1 & 2 from TB21-1 & 2. Reference voltage across leads must be 20 VAC or more. If not, troubleshoot according to Trouble heading, Field Circuit Breaker Keeps Tripping.
- Orion: Disconnect stator leads 1 & 2 from TB21-1 & 2. Reference voltage across leads must be 20 VAC or more. If not, troubleshoot according to Trouble heading, Field Circuit Breaker Keeps Tripping.
Defective commutating reactor CMR21
2 brands- Cummins/Onan: Shut down the set and check CMR21 winding resistances according to Servicing the Generator in Section 5.
- Orion: Shut down the set and check CMR21 winding resistances according to Servicing the Generator in Section 5.
Defective voltage reference transformer (T21)
2 brands- Cummins/Onan: Shut down the set and check T21 winding resistances according to Servicing the Generator in Section 5.
- Orion: Shut down the set and check T21 winding resistances according to Servicing the Generator in Section 5.
Voltage Regulator VR21 is faulty
2 brands- Cummins/Onan: Check voltage across TB21-3 & 4. Voltage across leads must be 7.0VDC or more. If not, check all connections against the wiring diagrams on page 7-7 and rewire as necessary. Replace the voltage regulator if the wiring is correct and there is no output voltage.
- Orion: Check voltage across TB21-3 & 4. Voltage across leads must be 7.0VDC or more. If not, check all connections against the wiring diagrams on page 7-7 and rewire as necessary. Replace the voltage regulator if the wiring is correct and there is no output voltage.
Blown fuse or circuit breaker.
2 brands- Cummins/Onan: Look for cause and repair. Then replace fuse or reset circuit breaker.
- archive.org: Look for cause and repair. Then replace fuse or reset circuit breaker.
Disconnected wire or lead on brushes, bridge rectifier or reactor assembly.
2 brands- Cummins/Onan: Reconnect wire or wires.
- archive.org: Reconnect wire or wires.
Brushes not making contact with collector ring.
2 brands- Cummins/Onan: Check brush springs for free movement or brushes which may be excessively worn.
- archive.org: Check brush springs for free movement or brushes which may be excessively worn.
Open, grounded or short circuit in field or armature winding.
2 brands- Cummins/Onan: Test with tester or ohmmeter and replace if defective.
- archive.org: Test with tester or ohmmeter and replace if defective.