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brownjeff, ASE Certified Technician
Category: Chrysler
Satisfied Customers: 13886
Experience:  17 years experience, ASE certified, dealership certified, Service Manager for 15 years,
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1999 Chrysler LHS: Battery light..Replaced alternator but light

Customer Question

1999 Chrysler LHS 117,000 - Battery light is on and only battery voltage available. Replaced alternator but light still on and voltage is still only battery voltage.
Submitted: 7 years ago.
Category: Chrysler
Expert:  brownjeff replied 7 years ago.
The voltage regulator for the alternator is located inside the powertrain control module (PCM). If you have power to the red wire and the orange with a green stripe going to the alternator then most likely the pcm has failed and needs replaced. You would need to check the wiring to know for sure, but based on what has been done most likely the problem is the pcm
Customer: replied 7 years ago.
This is not clear. Is the voltage check done on orange / green wire with it connected to alternator or not? What should voltage be? And is this done with engine on or off?
Expert:  brownjeff replied 7 years ago.
Key on for the test and should be around 12 volts
Customer: replied 7 years ago.
I'm sorry but this is just not clear. Is the voltage checked at the orange / green wire while connected to alternator or is it checked with the plug out of the alternator? What if there is no or low voltage?
Expert:  brownjeff replied 7 years ago.
You can check the wires either way on or off of the alternator. If no voltage there is a bad wire or blown fuse
Customer: replied 7 years ago.
I appreciate the effort but this leaves me with too much guessing--"most likely is the problem" might cost me hundreds of dolllars to replace PCM and find it is another problem. I am going to have to have someone do the testing with scan tool and meters to determine the real cause.
Expert:  brownjeff replied 7 years ago.
Correct. the wiring and voltage must be checked to determine if the problem is in the wiring or the PCM. No way to say for sure until the wiring is checked. Normally it is the PCM but can't assume with out testing the wiring

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