I went through all the same overheating issues with my Onan a few years ago. The main problem is the way the LQ conversion factory installed the generator with very limited ventilation. The intake air and exhaust air not being separated and ducted apart to eliminate recirculation of the heated air. This eventually causes the board to overheat and either shutdown or fail. Another racer informed me last year that Onan makes riser kits to elevate the generator, and has a divider and can pull intake through the front. This solved their overheating issue. It's unfortunate that the trailer manufacturers that install the generators do not follow the recommended clearances for ventilation provided by the generator manufacturers.
Without help from Rich I was ready to give up on a generator that had very little run time and failed every race we went to. I have ducted the exhaust air to discharge to the opposite side of the trailer from the intake air, and we have a box fan that also runs to ventilate the generator compartment.
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https://mart.cummins.com/imagelibrar...es/0058349.pdf