A generator control board must:
1. Receive a start signal from a manual switch or an outside source such as a remote switch or a system management panel. These could be positive or negative voltage signals depending on the engineer that designed it.
2. Process the signal to various sub systems and get the starter motor, ignition and fuel controls working. This function usually splits into two or more relays or circuits that control the final process.
3. Sense when the engine is running and turn the starter off or turn the starter off if the engine does not start. This is usually a voltage level that shifts the control from external battery power to internal rectified generator voltage power. On some models, the frequency of the voltage is used as a starter disconnect. Some gensets have a timer to stop the starter to prevent overheating of the starter motor or excessive running down of the battery.
4. Have and turn on a safety system after starting to protect the engine from malfunctions. This is usually a low oil pressure switch that has a delayed function until the oil pressure is up. On some gensets there is also an overheat switch either water or oil oriented that will shutdown the unit. Electronic governor systems also may shutdown on over speed of the engine as sensed by the frequency of the voltage.
5. Monitor engine parameters for speed, temperature, and pressure during operation and signal upon malfunction and/or stop the engine. The safety system constantly monitors the desired parameters whenever the engine is running.
6. Have systems for monitoring and controlling the generator voltage, frequency, and amperage load. Generator voltage is controlled by a solid state voltage regulator in most high quality gensets. Frequency is controlled by a mechanical or electric governor that keeps the frequency within set parameters. Amperage load is ‘controlled’ by the output circuit breakers on the genset. If the amperage gets too high, they trip the generator off the line.
7. Optionally – Have a battery charger. Most modern RV gensets only have a ‘trickle charger’ built into them as the converter in the coach performs the battery charging function. Some generators have battery charging as an add-on option.
8. Optionally – Have an external signaling capability for troubleshooting. The digitally controlled genset controls usually have self diagnosing control circuits built into them that can output a signal to warn of problems. This signal is usually a blinking light on the start/stop switch coupled with a rather extensive explanation section in the operator and service manuals.
Troubleshooting this control is usually covered in the “Service Manual” that is offered by the manufacturer at an extra cost. It also requires some knowledge of electricity and control systems.
(And you thought you could just throw a pair of pliers across the starter solenoid posts and everything would be all right.)
Generator Jim