Hi all,

I have a '98 F150 4.6, and recently the battery charge light has started to come on intermittently at low rpm, and I have noticed the charge meter going down to about half power on my drive home from work (only about 3 miles). If I turn on radio/head lights, the light stays on more consistently.

Would this be the alternator? It has a remanufactured alt. in it, but the truck has just short of 189K, and the alt. was replaced at least ~70K ago. I have never had any problems with the battery, and the light does not go on at high rpm. We are also in the midst of breakup up here, so there is water and dust everywhere.

Thanks for any help you can provide!


Jon

 

You can have both your battery and alternator tested at a local auto parts for free.
How old is the battery?

Reman alternators can last forever or sometimes fail in a short period of time. I had one that lasted 2 days. If the battery is older than 2-3 years I would just go ahead and have them both tested.

huh?

 

The battery is....5? years old, so I will have them both tested.

As for breakup, we had 124" of snow in town this year, and it's ALL melting right now. So there are huge puddles and gravel piles everywhere.


Jon

 

Ah gotcha. Never heard that term before. You can test them yourself if you have a voltage meter...? Battery should be at 12.5ish non running and 14.5ish running.

 

^ +1 check it with a meter. If the voltage doesnt change much after the truck is running, Id suspect the alternator. If the voltage is reading pretty low with the truck off Id look into the battery.

 

Battery was 12ish non-running and 14.5 running, so the battery is good. Even though it changed when I turned the truck on, should I be looking at changing the alternator?

 

I had the stock alt fail around 100k Bought a new one failed in 6 months. But it worked charged sometimes and other times not.

 

A 5 year old battery is up for automatic replacment, especially in your climate.
A voltmeter test does not take the place of a load test to determine the capacity conditions of the plates for sulfation or a high resistance internal cell strap condition.
If the charge light is glowing at low RPM, the alternator regulator is not turning off the lamp due to a low voltage charge condition.
Certinaly at higher RPM when the voltage goes higher the regulator will turn the charge lamp off.
Good luck.

 

Battery light usually means an alternator problem.

 

Sounds like alternator, but does the truck do any power rationing? Dim lights, raised idle rpm, that kinda thing?

 

Had the battery tested and the Alt looked at, both looked fine but the battery was showing slightly low, so I changed it out and the battery charge light is still coming on. Guy told me it could be my Alt. going out intermittently, would it be worth the cash to replace the alt. myself, or is it more likely there is some other type of problem (wiring, etc.) and I should have a mechanic take a look?

Thanks for all the help guys! Really appreciated.

Jon

 

Refer back to my reply#8.
The charge light is controlled by the Alternator regulator.
It turns it on and off.
If it's on for any reason, there is still a problem.
Even an aged battery that still starts the motor and charges up to the float voltage value will keep the light off if the Alt/Reg has no problem.
.
To say this more technically, the regulator has a reference circuit that the battery voltage is compaired to. When the voltage is lower, the Alternator trys to charge the battery to bring it up to the reference circuit value.
As long as all of it works the light is off.
If it is in fault, the light come on.
Good luck.

 

Alternator, change it , or have yours rebuilt.