RV generator running but no power to the coach

Common symptoms

• The generator starts and runs smoothly, but the outlets, microwave and air conditioner stay dead.
• The status light on the start switch stays on steady, so no fault shows, yet the RV has no 120V power.
• Power comes on a while after the generator starts, not right away.
• The RV works on shore power but not on the generator.
• The status light flashes fast while the engine runs.
• The generator runs, but the house batteries do not charge.

Quick checks before anything else

• The breaker on the generator itself is on. Push it fully off, then on.
• You waited out the transfer switch delay (up to 45 seconds on Progressive Dynamics switches).
• The main breaker in the RV panel is on.
• Big loads like the air conditioner were off when you started.
• The shore power cord is unplugged, or at least the pedestal is off, so you know which source you are testing.
• The status light is on steady, not blinking a code.

Why does the generator run but give no power?

• Generator breaker tripped or off Cummins says the generator keeps running when its own breaker trips, so the RV gets nothing.
• Transfer switch delay or failure The switch waits before it changes to generator power. Dirty or burned contacts can stop it from changing at all.
• Surge protector holding power off An EMS wired after the transfer switch checks generator power too, and adds its own delay.
• RV panel breaker or GFCI tripped The generator power reaches the RV but stops at the panel or a GFCI outlet.
• Overload Too many big loads trip the breaker or, on inverter models, the virtual breaker (code 38).
• Generator not making power On QG 5500 and 7000 models, a fast-flashing light means Engine Run Only mode: the engine runs with AC output turned off.

Step-by-step: RV generator running but no power

When your generator is on but there is no power to the coach, the engine side is fine. The fault sits between the generator’s output and your outlets. Cummins Onan’s own troubleshooting for “no power, generator set running, status light on” starts with the breakers, and so do we.

1. Read the status light On an Onan, the light in the start switch stays on steady while the generator runs normally. If it blinks a code after a shutdown, look that up first. On QG 5500 and 7000 models, a light flashing fast while the engine runs means Engine Run Only mode. Cummins says that after a shutdown for an alternator failure, restarting within one minute runs the engine with no AC output. That needs a Cummins dealer.
2. Reset the generator’s breaker The breaker is on the generator’s own control panel, not on the remote switch inside the RV. Turn off as many loads as you can, then push the breaker fully off and back on. Cummins notes the generator keeps running when this breaker trips, which is why the RV goes dark with the engine still humming. On the QG 2800i, the manual has you open the enclosure door to reach it.
3. Give the transfer switch time The transfer switch is the box that chooses shore or generator power. Progressive Dynamics transfer switches wait 20 to 45 seconds after generator power arrives before they switch over, and Cummins asks for a 2-minute warm-up before you load the generator anyway. Start the generator, wait, then test an outlet. Some transfer switches have a light that shows which source is live.
4. Check the surge protector If a Progressive Industries EMS or Surge Guard is installed after the transfer switch, it checks generator power too, and adds its own delay before passing it on. Read its code or lights. Progressive’s EMS shows E 7 or E 8 when the frequency is more than 9 hertz off 60. Southwire says a high-voltage fault on generator power means you should check the load balance and have the generator’s voltage regulator checked.
5. Reset the RV main breaker and GFCIs Push the main breaker in the RV panel and any tripped branch breakers fully off, then on. Press Reset on every GFCI outlet, because one can cut outlets in other rooms. If the RV also has no power on shore power, use our guide for an RV with no power when plugged in.

   

6. Add loads back one at a time Cummins says that if a breaker trips right away with loads off, an appliance or circuit has a short or the breaker is faulty, and to call a qualified electrician. If it holds, turn appliances back on one by one. If a breaker trips the moment one appliance starts, that appliance or circuit probably has a short. Start the air conditioner last: Cummins says it can draw 3 to 4 times its running power while starting, and a battery charger can pull up to 3,000 watts.
7. Restart an inverter generator after code 38 Onan inverter models like the QG 2800i have a “virtual breaker” built into the control. When load goes over the limit, the generator shuts down with fault code 38 instead of tripping a switch. Cummins says no reset is needed: cut the load and restart. The 2800i is rated 2,800 watts, or 23.3 amps at 120 volts. See the QG 2800i code list for the rest.
8. Compare shore and generator power If everything works on shore power but not on the generator, the transfer switch’s generator side or the wiring from the generator is the likely fault. Progressive Dynamics says the most common reason a transfer switch won’t change over is dirt on its contacts. Cleaning and testing them means working inside a 120V box, so that is a job for a tech.

Why the generator isn’t charging the batteries

A built-in generator does not charge the house batteries by itself. The QG 2800i manual puts it plainly: the generator does not charge vehicle batteries directly, but feeds a separate battery charger. In most RVs that charger is the converter, so if the outlets work on the generator but the battery stays low, the problem is the same as on shore power: see RV battery not charging when plugged in. Progressive Dynamics adds that voltage spikes from some generators make its converters shut down, and that adding another load may help.

The generator’s own starting battery is different. The diesel QD 6000 to 8000 models charge it at up to 10 amps. For gas models, Cummins says a starting battery that keeps running down needs the vehicle’s charging system checked.

Differences by generator type

Onan QG and QD built-in generators. These have a physical line breaker on the generator and feed the RV through a transfer switch. No power with a steady status light points to that breaker first. The QG 5500 and 7000 can also run in Engine Run Only mode after an alternator fault.

Onan inverter models (QG 2800i, 4000i, 7000i). These shut down on code 38 when overloaded. On the 2800i, Cummins calls this the virtual breaker, and adds a 30 amp physical breaker as backup. The generator keeps running if that one trips.

Portable generators. The RV’s shore cord plugs straight into them, so there is no transfer switch. Check the generator’s own outlet, overload protection and oil per its manual. For more on how RV generators work, see our RV generator repair guide.

When to call an RV tech

• A breaker trips again right away with all loads off.
• The status light flashes fast while the engine runs, or a code with no owner fix appears.
• Power works on shore but never transfers to the generator, even after the delays have passed.
• The transfer switch buzzes, smells hot, or has burned or pitted contacts. Progressive Dynamics says that damage points to generator voltage dropping below 90 volts under load, and that the generator needs repair and the whole switch needs replacing.
• The surge protector keeps reporting high voltage or bad frequency on generator power.

Common questions