Generac MTT15 troubleshooting: 16 fault codes and symptom-cause-remedy entries from the manufacturer's own service documentation.
Generac MTT15 — full specs, parts & maintenance.
| Symptom | Cause | Remedy |
|---|---|---|
| Unit stalls when export power is used | Load exceeds unit rating | Turn outlet breaker ON and load sense switch OFF, confirm generator output is 60hz + or - 2hz. Reapply load. |
| Low oil pressure | Oil pump inoperable: Contact a GMASD. | |
| Generator overheats | Check oil level. Add oil if necessary. | |
| One or more lights do not turn on | Light breaker tripped | Check light breakers. |
| Mast Lights OFF, checking outside the control box | Light fixture too hot | Allow light to cool 10-15 minutes before restarting. |
| Mast lights ON but light output low | Dirty fixture and/or lens | Clean reflective surface inside fixture and both inside and outside surface of glass lens. Use mild soap and water to clean lens. Other chemicals may have an adverse effect on the glass. |
| Generator output incorrect | Check the incoming voltage to the ballast. Incoming voltage should be 120V +/-5V. If the voltage is incorrect, the engine speed may need to be adjusted or the generator may require service. | |
| Low transformer output | The voltage from the transformer should read approximately 400VAC as the light 'strikes' (induces an arc), then drop and slowly rise back up to stabilize at 240–260VAC. On hard wired models, remove the mast junction box cover and insert the wire probes into the connector blocks for the light and ground. If proper voltage is not achieved, perform capacitor check to determine if the capacitor or coil needs to be replaced. | |
| No water flow | Clogged hose bibb(s) | Check hose bibb(s) for obstruction—clear debris |
| Engine not running; no power to onboard pump | Start engine to operate onboard pump. | |
| Onboard pump fault | Repair or replace | |
| Empty water tank | Fill water tank. | |
| Weak or interrupted water flow | Hose or hose connection leaks | Check for leaks—tighten loose connections; repair or replace damaged equipment |
| Onboard pump does not shut off | Faulty pump—water pressure is not reaching 35 psi (241 kPa) to trigger automatic shutoff | Repair or replace onboard pump |
| Engine cranks but does not start | Low fuel, Obstructed fuel flow, Air in fuel system, Restricted air filter, Glow plug(s) inoperable | Check fuel level in tank. Check fuel pump operation. Inspect fuel supply hose from tank to fuel filter for cracks and abrasion. Check for gelled fuel in cold weather, especially at fuel filter. Bleed air from fuel system. Inspect air filter for blockage. Refer to OEM engine operator’s manual for additional information. |
| Engine starts, then stops | Ambient temperature too low, High coolant temperature shutdown | Check ECU codes. Check if ambient temperature is within unit limits. Allow engine to cool. Check coolant level in radiator; add coolant if needed. Inspect radiator. Remove blockage and any debris. Inspect for visible leaks. Check tension of water pump drive belt. Remove load on generator and restart engine. Check coolant temperature and shut engine down immediately if it exceeds the limit. |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
Documented causes: Load exceeds unit rating. See the table for the matching fixes.
Documented causes: Light breaker tripped. See the table for the matching fixes.
Documented causes: Light fixture too hot. See the table for the matching fixes.