My GM 840 once shut off would take about an hour or more to come back on. Then it started to be more difficult. The fan would run but the light in front wouldn't come on but again after hours it would come on and be fine. Now it shut off on its own and will not come on. The fan runs and the first few times I shut it off and tried to get it to come back on the light on the front button worked. Now no light but the fan runs and it will not come on. Does anyone have any ideas.