was anything changed or upgraded right b 4 this started happening?
New batteries perhaps?
Or have you noticed any slow change in the performance of the system lately?
Or do you not use it much?
Any chance the batteries were allowed to freeze last winter?
I agree with the poster who suggested checking your batteries first. As in pull them out, charge them with an external charger, and test them, both a load test and a hydrometer test. (poor mans hydrometer test: take the caps off, put a voltmeters neg lead on the neg terminal, and stick the positive lead in the cells one at a time nearest to farthest. Voltage on the meter should increase around 1.7 volts each cell. dead or shorted cell = no voltage increase.)