Any of several problems with the control circuits may require RV generator repair. Learn more below about the most common causes of damaged control circuits in your RV generator and how to fix them.
What the Control Circuit Board Does
The control circuit board controls and regulates the operation of many functions in the RV generator. Among these are ignition engage and stop, control of the fuel pump and solenoid, protection of the circuit fuse, operation of the electric choke, and shut down of the generator due to low oil pressure.
Dirty Control Board
Keep the control board clean and grease free for optimum function. It can be cleaned with #2 - 26 cleaner for electrical contacts. Use as little water as possible, and dry the board on low heat with a hair dryer. Apply a degreaser to the board to remove grease and prevent new deposits. After cleaning, cover the printed board with several light coats of acrylic resin conformal protective coating on both the printed circuit side and on the side with no terminals.
Distorted Female Sockets
After many hours of use, the female sockets on the control board can become bent or distorted from their original round shape due to heat. Use smooth needle nose pliers to reshape the female sockets to their correct round shape.
Incorrect Voltage / Resistance on the Terminals
Check the voltage with a voltmeter for the various terminals on the control board. The 9 to 1, 10 to 1 and 11 to 1 terminals should show a voltage above 10 volts DC when the starter is on. If the voltage is lower, check that the fuse is operating correctly.
Check the terminals for corrosion. Clean them and apply an anti-oxidant grease to the terminals to protect them from corrosion. If K2 and K3 terminals are burned, corroded, or no longer functioning, replace them with exact duplicates.
Diodes CR1, CR5 and CR6 can become damaged due to kick back from the choke solenoid at a high voltage. Diode CR7 can become damaged if the CRt5 diode fails. Replace any of these diodes with the 400 volt, 1-amp 1N4004 diode as needed.
Low Charge on Battery
The battery may not be providing enough charge to start the generator. Check the battery terminals and test the battery charge with a voltmeter. If the battery shows sufficient charge, clean the battery terminals and apply an anti-corrosive and antioxidant to the cable ends and the battery terminals.
Low Oil Pressure
A condition of low oil pressure in the RV generator can damage terminal 12 of the control circuit board. Test the switch and wiring for low oil pressure by removing the terminal 12 connecting wire and testing for resistance. When the generator is off, the resistance should measure near 0 ohms. If the test shows this result, reattach the terminal 12 wire and start the engine again, then turn it off. There should be a delay of 3 to 5 seconds before the engine stops. If there is no delay, or the engine does not stop, the circuit board has malfunctioned. Replace it with a genuine Onan control circuit board.