Toyota Repair: 1987 Toyota 4-Runner, negative battery cable, mile road trip


Question
1987 Toyota 4-Runner, 4 cylinder, 22RE engine, 4 wheel drive, 210k original miles (30k on a rebuild), originally from hot desert climate.

Starting problems on and off for a couple months. Sometimes won't turn over. Sounds like dead battery, clicking noise. Thus far truck has always eventually started; seemingly new reason each time (replaced connector on secondary starter wire, removed alarm system with possibly poor wiring, replaced negative battery cable & confirmed solid grounds, replaced starter relay)

July 4th, 300 mile road trip, truck wouln't start next morning. Unlike usual problem, truck does try to turn over but cranks very slowly. Starter sounded to be groaning. This time truck won't start. Tried new starter only to receive same results. 6 month new battery has been tested & is fine.

Any advice?  

Answer
Have the charging system tested it sounds like there may be an alternator problem, if you have access to a voltmeter connect it across the battery terminals while the engine is running, you should read between 13.8-14.7 volts, anything below 13.8 means the alternator is not charging enough and draining the battery down.