In my 2012 f150 xlt I changed the alternator and now every time I start it the battery light comes on and dings every 5 mins anyone able to help me? Also I have a trailer brake module fault always on but I dont have the normal brake controller in the cab any help with both of these thing are much appreciated

 

What brand alternator? These trucks seem to prefer Ford/OEM alternators for whatever reason.

 

One from Napa it just says napa rotating electrical

 

next step is wiring check, i have priced a few PCMs for this issue

 

I would suggest a re-manufactured motorcraft Alternator... like stated above, our trucks are very picky about the voltage regulator in theses alternators.

 

Why exactly did you replace the alternator? What test did the original one fail? Before anything else, click these & read the captions:

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