issues with low rpm light dimming

[ColdVoid]

hi guys its been a while since i got on i hope all is well with everyone. i have a 2000 expedition xlt 5.4 and i have been noticing mt lights dim and my blowers get weak under breaking and idle i know im due for a battery but i was wondering if a weak alternator would cause this? i replaced it two winters ago. or could it be an amp problem like i got one to small? any feed back? thank you and god bless. any help would be appreciated

 

[Plati]

You need to start with a voltmeter. Measure voltage at battery posts under various situations. Engine not running. Engine starting. Engine running no headlights. Engine running with headlights. Thats how I would start.

 

[stamp11127]

Seeing that you are in a state that uses salt during the winter I would do a voltage drop test on the charging circuit. You can do that with a standard voltmeter or DMM. If you have corrosion in any of the wiring connections to the battery/alternator combo it will lower the voltage and amperage into and out of the battery. There should be a sticky in the electrical section on how this test is performed on any part of a circuit. Any questions just ask.

 

[ColdVoid]

Seeing that you are in a state that uses salt during the winter I would do a voltage drop test on the charging circuit. You can do that with a standard voltmeter or DMM. If you have corrosion in any of the wiring connections to the battery/alternator combo it will lower the voltage and amperage into and out of the battery. There should be a sticky in the electrical section on how this test is performed on any part of a circuit. Any questions just ask.

Do you know what the amp/voltage should be at?

 

[stamp11127]

Battery at 100% soc is 12.6v
Charging voltage engine running @1500 rpm is 13.5 - 14.5 v
Amp output is dependent on the alternator rating but should fall between 110 - 200 amps. You'll need a DC Amp clamp for that reading.
Acceptable voltage drop is .5 v total for both positive & negative sides of a circuit. Circuit being tested needs to be energized for an accurate reading.

 

[butch cook]

have the charged battery load tested first.start with the obvious . autozone and others test and will replace the battery .sounds like a dying or dead cell in battery