Frequently Asked Questions About Generac Mobile

Some questions are more common than others. Explore the FAQs below to obtain insight on the products that interest you the most.



Why does the unit start but shutdown after 15 seconds?

If the fluid levels are all accurate, this is usually caused by a faulty oil pressure switch or high coolant temperature switch. To verify, remove the grounding wire on each switch (one at a time). If the unit starts and continues to run beyond 15 seconds, replace the switch.

Why do the lights turn off or flicker, then come back on?

The plasma arc within a metal halide light is self sustaining, provided sufficient power is provided to it (see 'How do metal halide lights work?'). If the generator voltage or frequency dips, even momentarily, the plasma arc is lost and requires the 'start' circuit to reignite. A heat sensitive metallic strip within the lamp must cool sufficiently to disconnect from the 'run' circuit. At this point, the 'start' circuit is reenergized, and the lamp is reignited.

How do metal halide lights work?

Metal halide lights utilize two circuits for operation; a 'start' circuit and a 'run' circuit. High voltage (~400V) is used to strike an arc across a small gap at one end of the arc tube. Temperature and pressure increase as this arc is sustained, ionizing the metal halides within the arc tube. Additionally during this 'starting' process, a heat sensitive metalic strip expands and eventually closes to the run circuit. At this point, the metal halides have provided a conductive path across the length of the entire arc tube. As long as sufficient power is provided across the circuit, the plasma arc will sustain itself.

Why won't any of the lights turn on?

If none of the lights will turn on, the issue is usually generator or generator capacitor related.

Why does one light turn off when another is turned on?

If turning on one light causes another to turn off, this is usually related to a faulty coil cord.

Why won't one of the lights turn on?

If only one light won't turn on, the lighting capacitor or transformer may be faulty.



What is wet stacking?

Diesel engines operate by compression ignition, in which the air/fuel mixture are compressed until auto-ignition occurs. As the load level is increased on the engine, cylinder temperature will rise, increasing the amount of fuel that combusts. If the engine is lightly loaded, unburned fuel will enter the exhaust manifold, pipes and turbocharger, building up over time. This is evident from black exhaust smoke during steady state operation. In order to reverse a wet stacking condition, the engine must be heavily loaded for an extended period of time.

What are the consequences of lightly loading a genset?

A lightly loaded genset doesn't produce enough heat to sustain every sub-system within the generator, mainly the after treatment and other emissions related components. While this does not have long-term consequences from short durations or infrequent situations, long term light loading can cause sub-system failure from wetstacking, DPF clogging, EPR valve freezing, and others.

What is considered lightly loaded?

A generator is considered lightly loaded below 30% rated load.

What is Regeneration?

Some interim and final tier 4 diesel engines are equipped with a Diesel Oxidation Catalyst (DOC) and Diesel Particulate Filter (DPF) that reduce diesel particulate matter from being released into the atmosphere. Regeneration is the process of cleaning the DOC & DPF. If the unit is properly loaded, regeneration occurs passively from elevated exhaust temperatures. If the soot load level exceeds 60%, active regeneration will occur, during which diesel is injected into the filter to dramatically increase the exhaust temperature. Between 80-100%, the engine will automatically de-rate 50% which can cause issues with connected electrical loads. If the engine exceeds 100%, service regeneration is required.

What is HEST?

HEST stands for High Exhaust System Temperature. When the engine is in an active or forced regeneration cycle, diesel fuel is being injected into the exhaust after-treatment to burn off the accumlated particulate matter. This dramatically increases the temperature of the exhaust.