The first thing you should do when you have a Alternator or Starter problem is to have the battery tested.
Anytime you replace an alternator you should do a voltage drop test on the Charging circuit. The single biggest cause of repeat failures of alternators is voltage drop. (I work for a manufacturer) The easiest way is to check the voltage at the alternator and then the battery. Do so with the lights on and the engine at 1200-1500 RPM. The difference should be no more than .5 Volts. If it is higher, check each side of the circuit.
Positive side: red lead at the output post of the Alternator and black lead on the positive post of the battery. Record the voltage (it should be low)
Negative side: Black lead on the case and red lead on the Battery negative post. again record the voltage.
Concentrate on the side that is the highest voltage drop by checking all connections and cables. You can test each one with the volt meter by placing the leads (same operating conditions as above) on each side of a connection (for Example where the Ground cable attaches to the block put one lead on the cable terminal and one on the block near by) or at each end of a cable. Each connection should be .01V or less. Cables will depend on length.
Oh and if the system has a Field wire (a separate wire to provide voltage to the field windings) going to the regulator connection check the voltage on that wire under the same conditions, it should be within a .5V of the system voltage. If it is not the system will overwork itself because it cannot build a sufficient magnetic field around the Rotor.
Same goes for a Starter, measure the voltage at the battery and the starter while cranking. It should not be more than .5V different. If it is, do a voltage drop on both sides of the circuit using the methods cited above only between the starter positive post/case and battery during cranking.
Do not forget, the ground side is just as important as the Positive side as the current has to follow the complete path from one side of the battery (or alternator when charging) to the other. (Actually the current path is negative to positive but the automotive world favors conventional flow)
Tip: Never place a washer between two cables on the same post nor between the cable and the contact point i.e. Battery + post of a starter or alternator or cable end and engine block etc.. Most washers are zinc and will carry current initially but will build resistance quickly.
Last edited by skborders; 01-25-2014 at 06:49 AM.
Reason: Added content