Is my alternator not charging?

DJBEN

MEMBER
2002 FORD MUSTANG
V8
2WD
MANUAL
133,000 MILES

Recently, I noticed that when either brake light, the headlights and even backlight from the dash and or radio are on, I can see continuously small dim in the electricity of the car. I have noticed that regardless if I give gaz or not (to have the alternator go faster), it doesn't change much. One thing I noticed however is that the continuous dimming seems to fade when the car is getting warm. I have replaced the alternator with a brand new one about 6 months ago and just noticed this problem. My battery is getting pretty old, so I bought a new one, but haven't installed it yet although I haven't had any problem cranking the car so far. Would you have any idea what the problem might be?

1 Reply

KASEKENNY

MECHANIC
18,907 POSTS

This is almost guaranteed to be a wiring issue. Basically it sounds like you have high resistance most likely in a fusible link.

Here are a couple guides that will help with this:

https://www.2carpros.com/articles/how-to-check-wiring

https://www.2carpros.com/articles/how-to-check-a-car-alternator

What I would do is check the voltage at the battery junction block and make sure you have 12 volts. If not then measure the resistance through the links and it should be less then a half ohm.

Please run through this and let us know what you find. However, if these check out then make sure the ground is tight at the battery and the grounds shown in the diagram below.

Please let us know if you have other questions. Thanks

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