1986 305 TPI (F engine code)...SES shows code 53 (over voltage, 17+ volts at ECM for 2 seconds)...45-75 mph voltmeter will ride steady about 14v then spike up to 18v+ and then drop off to 14v again...also showing code 32...cant get the voltage spike to happen in idle or with engine rpm up around highway speed in park...only when driving (usually at highway speeds) tried idle with trans in gear too and no spike...had battery load tested and its good...had the alternator tested and its fine too...where should i go to from here?...thanks in advance...mike