I have the standard Vans provided Plane Power 60 amp internally regulated alternator. It has started having unstable voltage, up to 15.2 volts. This seems to happen when it gets hot; at the start of a flight, the voltage is low 14s but later gets up to the 14.9 - 15.1 range. I wonder if this is a cooling issue. The way the cowl is set up there is no provision for cooling air to reach the alternator. Have others had this problem? Solution?