Hi. we just changed generator on a 3500 5.7L, 105 amp alt. Charged battery full and have appx 15 amps on gauge. however after about 2-3 mins of idling the engine rpm's increase drastically. The van does 30 mph down road without touching gas pedal when we drove it. if turned off for about 15-20 mins it starts and drop's to a normal idle for a few minutes but starts racing again. We removed the air horn assembly and the wire connector to it but plugged back in before reinstalling battery. Also removed the reserve water tank for access to tensioner. Thanks for any input you may have. Frank k