Other's are welcome to correct me if I'm wrong... But I believe that the alarm going off will disable the ignition. Thus the lack of spark. So the problem may just be entirely in the alarm system. Search this forum for alarm system problems. Have you checked for corrosion in the positive battery cable? You have to sorta peel back the insulation at the battery post connector and look "inside". This cable may look good on the outside. What was the symptom that caused you to change out the alternator?You may have some underlying electrical problem. Good Luck!

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