Aqua Hot Diesel Not Lighting in Systems and Appliances Posted March 27, 2016 · Report reply I have an Aqua Hot 400-D in a 2015 Tiffin Phaeton 40-AH (all electric) coach. Yesterday the temperatures were warmer, so I'd turned the diesel boiler off, leaving the electric on. This morning when I turned it back on to get heat, the diesel didn't start or ignite. When I look at the indicator lights on the control panel, everything that's lit is green, including: Electric Heating Element Status, Heating Zone Status #1, Low Temp Cutoff Status, Pump #1, Diesel-Burner Status. Inside, the heat exchanger fans are blowing cool air. When I turn off the diesel boiler for 30 seconds and turn it back on, a pump comes on briefly, then goes back off. At least that's what it sounds like. Up until now (since January, we're full-timers), it has been our main source of heat, not to mention hot water.