1998 f150 4.6 battery light stays on all the time so i got the battery and alternator checked they checked out just fine nothing wrong and also at night when driving down the road i press gas pedal to the floor and the headlights dash lights and all get weak i need help to

 

Do you have a digital multimeter? If not, buy one ($15-50) and read these captions:

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How was the battery and alternator checked ?

The statement of "got the battery and alternator checked they checked out just fine nothing wrong" is a bit vague.

 

check your ground straps

 

i got it checked by a computer the comp was very accurate it checked alternator starter battery they all checked out fine matter all specs were average but the alternator put out exactly as it should

 

thats what i was thinking patman it has to be the ground i would think i will keep you posted when i figure it out

 

i have the same problem after i changed my alternator 3 years ago, i have done the big 3, so i know my issue is not a ground, the only thing i can think of is when i changed it i left the battery hooked up and accidentally sparked the wires, the fusible link is still in tact so i don't know what it could have been other than it frying the pcm. but then again when i was looking for an answer someone said if its not a ford alternator it could show the light....not too sure on how valid this is. but 3 years later my light is still on and i have just forgotten about it

 

most battery testers only test for DC output, if you have a blown diode in the rectifeir (changes AC output of alt. windings to DC) you can have DC but not enough under loads and the AC passing into the system can cause fluck-su-ations

 

it was the ground i unhooked it and then hooked it back up the battery l;ight is now off now all i want to see is smart azzes trying to jank me on how i type or some jerk off telling me how unprofessionnnull it is of me to type this way hahahah you jerks crack me up lol