I hope I'm allowed to post this here... If not please disregard and know that I'm sorry.

My 2004 Mercury Monterey broke down last night (all electronics shut off and it came to a sputtering halt) due to a bad alternator. I replaced it this morning and, after a jump, the car has run fine all day (drove for about 40 minutes). However, the battery light/check charging system light is still coming on while driving. I'm wondering if this could be because the battery is still low and is recharging, or if there is still another problem with the alternator, wiring, etc. Maybe the bad alternator ruined the battery? Anyway, any thoughts are appreciated.


  • If the light is still on, then there is another fault still to find... did you test the alternator & battery? Perhaps the alternator was not faulty...
    – Solar Mike
    Commented Apr 8, 2019 at 4:47
  • The only testing I did was seeing if it would drive without dying for a while, a decision I regret. I should have gotten it tested. My current suspicion is the battery or the PCM connector (maybe a wire is loose?). I'll take it in tomorrow to get it tested. Something was fixed by changing the alternator because now it drives, but I'm not convinced it was the only problem. I just hope I didn't waste $150 on a new alternator...
    – Guest112
    Commented Apr 8, 2019 at 7:50
  • 2
    It would be worth getting your OBD codes checked, the cause may become apparent. It's also possible the new alternator hasn't been put on right or has a fault. Check the belt is tight.
    – GdD
    Commented Apr 8, 2019 at 7:59
  • Just got the alternator, starter, and battery tested. All came back good and the car is still running and starting fine. The light is the only indication of an issue. Someone suggested a loose connection on the battery, but it's charging fine, so is that possible? I'll clean the connections later today.
    – Guest112
    Commented Apr 8, 2019 at 21:24
  • You can spend hours cleaning this, and checking that in the hopes of figuring out what’s wrong. The problem is, 1) it’s all wild guesses, 2) you won’t know if what you do has any effect because normally, the PCM has to go through a couple or a few cycles before it clears the code. Get a code reader. It’s a tool worth having
    – Allan
    Commented Apr 8, 2019 at 23:42


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