Check for defective diodes, attach a digital multimeter at the B+ terminal on the alternator, ground lead to battery or alternator case. Switch DMM to A/C volts, start engine and note reading. If cable operated throttle, raise RPMs with a gloved hand, if a DBW system, get a buddy. At 2,000 RPM A/C voltage should be well below 0.20 - 0.015 Vac. A leaking diode allows A/C voltage to appear on a DC voltage system. Too much and digital serial data problems arise as a noisy signal cannot be read by modules. If painted brackets, find a thread hole on the alternators end housing, measure depth with a pocket screwdriver, include the thickness of a copper or plated connector for bolt length selection. Attach the cable (8 AWG or lower) to the bolt and to the block or back to the battery. Use a “Star” washer to dig into metal and dielectric grease to protect it from corrosion. Use compressed air thru the holes in the alternator to make sure it is free of obstructions like leaves, husks from farm plants, etc. This too, ensures the cooling can remove heat from the diodes. The end case is where ground is directed and this as well, ensures proper complete circuit without voltage drop or loss thru painted parts, rust or previous corrosion. Hope this helps you understand how to extend the life of the alternator and a properly working vehicle electrical system. Certified Automotive ASE Master Tech since 1978.
