I am having challenges starting my 1976 Eldorado. After years of being able to start it despite the season, it now will inconsistently turn over. The battery has been checked, found to be in good shape and charged. Discovered the batter cable to connection to the starter was not tight. The battery cables have been replaced and tightened on both ends. These remedies resulting in the engine starting. Car was run for ten minutes. Stopped. Started again tweny minutes later and driven around for twenty minutes. Then after sitting for a half an hour, it will not turn over even if it is being jumped by another running vehicle. The Stop Engine Temperature light illuminates when the key is turned to the start position, yet it will not turn over at all. Any recommendations of what to check next are greatly appreciated.

Jim in Bozeman, Montana