Bronco L6-300 4.9L VIN Y 1-bbl (1983)
Fig. 15 Testing rectifier bridge diodes
FIELD OPEN OR SHORT CIRCUIT TEST
Exc. Alternators W/Integral Regulators
Using a suitable ohmmeter, connect the alternator field terminal with one probe and the ground terminal with the other probe, Fig. 15. Then, spin the
alternator pulley. The ohmmeter reading should be between 2.4 and 25 ohms on 1980 units, 2.4 and 100 ohms on all 1981-85 units and 1986-87 models
less IAR system, and should fluctuate while the pulley is turning. An infinite reading (no meter movement) indicates an open brush lead, worn or stuck
brushes, or a bad rotor assembly. An ohmmeter reading of less than 2.4 ohms indicates a grounded brush assembly, a grounded field terminal or a bad
rotor.
Fig. 16 Alternator w/integral regulator field open or short circuit test
Alternators W/Integral Regulators
1.
Using a suitable ohmmeter, connect regulator A blade terminal with one probe and the regulator ``F'' screw head with the other probe, Fig. 16.
2.
Spin the alternator pulley and note meter reading, then reverse probes and repeat step 1. In one probe direction ohmmeter reading should be
between 2.2 and 100 ohms and may fluctuate while pulley is turning. In the other direction, reading should fluctuate between 2.2 and
approximately 9 ohms.
3.
An infinite reading (no meter movement) in one direction and approximately 9 ohms in the other, indicates an open brush lead, worn or stuck
brushes, defective rotor or a loose regulator to brush holder attaching screw.
4.
An ohmmeter reading less than 2.2 ohms in both directions indicates a shorted or defective regulator.
5.
An ohmmeter reading significantly over 9 ohms in both directions indicates a defective regulator or loose ``F'' terminal screw.
6.
Connect alternator rear housing with one ohmmeter probe and touch the other probe to the regulator ``F'' terminal. Reverse probes and repeat test.
Ohmmeter reading should be infinite in one probe direction and approximately 9 ohms in the other.
