Charging Light under WOT

[hammerg26]

1999 Eddie Bauer 5.4 with 136k on it.
Under WOT, at about 4500 RPM, the charging light will come on. As soon as it shifts or drops RPMs it goes off.
Any ideas???

 

[docraymund]

Alternator problem most likely. Try to substitute it with a known good unit to see if the problem persists.
Also check v belt to see if there are any signs of slippage (shiny areas).

 

[stamp11127]

With engine running watch the movement of the belt tensioner, it is only allowed at max a slight movement up/down. It shoulkd appear steady with no movement. If it is bouncing the spring has weakened and the serp belt slipping.

 

[Mediamonkey11]

Belt tensioner is my guess, the angle even with a stock size pulley between the tensioner and the alternator is very dependent on full spring tension.

 

[Yudaman]

I had that same exact issue on my '99.
Alternator was the problem. More specifically, voltage regulator, but the alternator is internally regulated.

 

[hammerg26]

Ok.

 

[98eb5.4]

belt could also be worn (stretched) out

 

[hammerg26]

It was the alternator. I replaced the belt first - no joy. Replaced the alternator and issue went away. Just hope the Duralast Gold one works well.

 

[AbbadonTD]

with a name like Duralast, I dont expect it to.

 

[hammerg26]

Lol. I hope you are wrong.