I have a 2006 f150 5.4. I've had the alternator changed twice now because the amps were reading between 60 and 70. My mechanic said it should be around 120 (I think). So, my lights still flicker and so does my dash (mainly my odometer). It's not bad when it's cold, but when it warms up it gets pretty bad. It doesn't flicker any if I'm driving, only when I come to a stop like at a light or anything. What could this be? I'm not a great mechanic so I need help for sure. Thank you.

 

The alternator only generates the amps needed to keep the voltage to about 14 and the amps needed to do that varies with load. How did the mechanic test it?

 

I'm pretty sure they used the meter to check it? I'm not positive. They're very good and honest and they're not sure why it's still doing that. When I accelerate it's gone so it's confusing to me.

 

What is gone when you accelerate ?

As Roadie posted the PCM decides what the charging rate is.

 

the flicker of lights and odometer is gone when I'm driving. Only at idle is it bad. So what does that mean? Could that be a battery issue? I mean the battery tests fine but could it still be that?

 

Sorry for this spam, but does anyone have any idea? I'm clueless. I can't figure it out

 

You need to put a voltmeter on the battery and watch both it and the amp meter to find out what's going on. When LA batteries start to go bad they won't take a charge, even though the battery charger or alternator IS putting out enough voltage. If you're getting low/no current but with about 14 volts then your alternator is ok and your battery is probably bad. It might take some time for your battery to get a full charge (over 13 volts) but it should and you should see current being produced until it does get a full charge. Once your battery is fully charged, the voltage regulator will turn the alternator output down or completely off so you will see see a small or no current flow.

FYI, your alternator is capable of producing 120 Amps but it should need to produce that much only RARELY. Also keep in mind that other electrical loads (engine, lights, AC, emissions controls, radio, etc) will all consume power so not all of the power produced will be available for battery charging. If you really want to know if your alternator is capable of producing 120 amps you need to connect a load tester to it. Most auto parts stores will load test them but you'll have to take it off and take the alternator to them. But a good auto electric place or a GOOD shop should have a portable load tester and be able to test your alternator in the vehicle.

PS in THEORY you could connect a load tester in a lot of different points in your auto electric system BUT MOST of the wiring isn't designed to carry that kind of load so you could burn up your truck's wiring if you don't know what you're doing!

 

flicker of the odometer in the info center is a most likely a different issue, so leave that one to the side for now.

What modifications, if any, have been made to the truck.
- If nay exist please list all of them, not just what could be applicable.

considering the wiring to the alternator has been messed wit a few times, have you checked that the connectors on the alternator are not damaged ?
- this is both connector C102A & C102B