I installed a Solaronics Radiant Tube Heater and for some reason the Ignition Detection control keeps failing . every three years is this normal for these heaters?solaronics changed the original control on the first one that burnt out to a fenwal 35-725911-117 now that one is acting up . did they or do they have a bad run on these controls ? Model is a ST-40 10n , Serial is St-03 5905 checked all that apply to repair problems all check out fine .