I have a 2000 F150, 2wd, 4.6 that when you accelerate hard the rpms jump to approx 4500 and the batt light comes on. Can anyone help me? Vehicle runs great otherwise

 

If it's a standerd, sounds like your clutch is slipping.

 

No, it's an auto, and the vehicle does accelerate, it's like the computer isn't preventing an over rpm condition

 

If the battery light comes on at high RPMs, I would get your alternator checked out.

 

I agree with Johngs have the alternator checked and go from there. sounds lke it might be bad

 

belt slipping????
can't see bad bearings free-wheeling....

 

There are clutches in an auto too. They are just not controlled by you as much. They depend on rate of accel which directly correlates with RPMs. If the truck is getting to high rpm with less than normal speed, the the internal clutches are probably startingn to go. Baby it, and you may get a few more miles out of it

As for the charge. Mine will periodically around 5000 rpm flash the alternator light. A test of the alternator shows is still putting out 14.2 volts no load, 13.7 under load and thats within spec. The high rpms must be giving it a hard time. Take a volt meter, start it up and test the voltage on the battery. If its between 13.4 or so and 14.2 then its ok. When they start dropping below 13 it time to get a new one.

 

An ALT light at high RPMs means the brushes in the alternator are starting to "float", loosing their connection to the commutator shaft and causing alternator output to drop out. This is uysally an early warning that your alternator is almost due for rebuild/replacement.

Steve

 

No, the point I'm trying to make is that the rpms are going higher then it has in the past. I get full acceleration with the rpm climb but it's about 800-1000 higher then normal. I think the alternator light has to do with the rpm, maybe the regulator shutting down at such high rpms

 

I noticed my truck doing this also while i was out playing tonight, i would reach RPM's around 5500 to 6000 and then the batt light would come on.

I was just looking for some info on it, thought my alt was on its way out but maybe not.

 

The rev limiter is a PCM function that's controlled by the crank sensor. You can check the crank sensor or replace it, and that might be your problem. Good luck.

 

Where will I find the crank sensor?

 

It sounds like you have two different problems.
The fact that the battery light is coming on is seperate from your RPM issue.
I would still go get the alternator checked out if I were you.

 

I don't know about the altenator, the light only comes on when the rpms are exceeding the normal range.

 

Yes, thats the point. Eventually the light will start to come on at lower RPMs.
AutoZone will check it for free.