Motor starts and runs fine but if cruising at 3500 rpms or more for more than 5-7 minutes the overheat alarm goes off and motor enters limp mode. If run at idle for about 2 minutes the alarm goes off and it runs fine for a few more minutes and then the alarm again. Impeller and thermostat are new. Tell tale has a strong flow at all times. Thermo switch looks ok, but it is original and I have not ohm tested it yet. Any other ideas?