Scott, You mentioned that you had cleaned the fins on the jugs.I just wanted to make sure that you had pulled the bottom access sheilds open underneath each exhaust manifold to clean there also.Many operators don't know about these sheilds because they have never been pointed out to them.Also,you can check your sender with a voltmeter.An open sender would have 12 volts,at 100F.-8 volts,400F.-5 volts,and a shorted sender would have 0 volts.Another thing to check that we have run across is to make sure that your engine high idle is set correctly.We had a R60 that had the same complaint as yours and found that high idle was set at rated speed,which meant the only way for the engine to build HP was to lug the engine which in turn made the head temp. light come on.Once we cleaned the fins and set the engine with high idle specs.,(found in your operators manual)no more problem with the head temp. light coming on.Hope this helps,Hyper Harvest II.