Search for "suburban water heater service and training manual" . I found a copy here: http://techsupport.pdxrvwholesale.co...ing-Manual.pdf
. Troubleshooting begins on page 16.
When my Suburban heater failed (hot air blower thingy under the rear seat/bed), it was the "board", but your problem could be something else. I replaced my board with an improved board from Dinosaur Electronics. The water heater may have a board, too (it controls the start sequence, among other things).