altenator trouble

[price_tag_1970]

changed altenator twice and got a new battery volt tester still say alternator is not working. i can let the car run but it just drains the battery. any ideas?

[kimbo99]

Wow, two alternators!? First you did not state if this is a 3.8L or 3.5L Intrigue. I’m not familiar with 3.8L, so this response assumes you have 3.5L, but may apply to 3.8L.

When you removed the first alternator, did the parts store have an alternator tester and verify the alternator was in fact bad? The alternator field coil is controlled by the PCM which turns the field current on and off about 400 times per second (according to my shop manual). So it is possible the PCM is bad or there is a bad connection between alternator and PCM. If you can, verify continuity between alternator terminal connector C pin (22 AWG grey wire) and pin 29 of the PCM C2 connector. Also verify continuity between alternator terminal connector B pin (22 AWG red wire) and pin 61 of the PCM C2 connector. Unfortunately (according to the alternator schematic), there is no way to verify the field coil resistance from the external alternator terminals.

Another (much easier) thing I would check is make sure you have continuity between the alternator output and the battery (the big 8 AWG red wire). This wire has a fusible link that could be blown.

Another item you should test is make sure there is not a high battery drain when the engine is turned off. Disconnect the negative battery cable, charge your battery, then with everything turned off, touch the negative cable to the battery. There should be an initial small spark, but thereafter the current draw should be less than 0.1 amp.

Finally, if you have an inductive ammeter, or access to one, verify that there is in fact no alternator output current with the engine running.