I installed a 250amp alt. in my 2007 F150 with the 5.4.Not the battery light is on on the dash.Any ideas?

 

Have the battery and the alternator checked. Just because it's new doesn't mean it's good.

 

^x2 we had a new alternator put on our 99 and it went bad less than six months after we got it

 

Let me guess; the alternator you bought was a rebuilt one from your local parts store? Around 60 to 70 bucks (or less)?

Cheap stuff using cheap parts. I'll bet it has a lifetime warranty. Good, as you'll be replacing it often.

Nothing beats OEM when it comes to electrical parts. You pay more, but they last, and won't fail you at the most inopertune time.

 

Hell yes!! While my 04 F-150 is stil stock, my 02 Explorer needed a new alternator at 150k. Re-manufacturerd one was bad. But not in a way that was immediately recognizable. Since I changed the belt the same time (I change belsts every 50k) we al thought it was the belt. 2 belts later it was the alternator.

Electric -- go with known quality.

 

[QUOTE=Bucko;1182946]Let me guess; the alternator you bought was a rebuilt one from your local parts store? Around 60 to 70 bucks (or less)?

Cheap stuff using cheap parts. I'll bet it has a lifetime warranty. Good, as you'll be replacing it often.

Nothing beats OEM when it comes to electrical parts. You pay more, but they last, and won't fail you at the most inopertune time.[/Q



NO............... This was custom built by a local shop.I know that the alt. is regulated by the computer and I think that is where the problem is.

 

The Alternator is regulated by the computer?

Damn, these ECUs are getting into everything these days.

To truly "Custom build" and alternator would take thousands of dollars, and time a local shop doesn't have. More than likely it's an off the shelf "custom" they bought from a brand X distributor.

The ECU doesn't control the alternator, there's a diode pack in the alternator which controls the voltage. With a cheap rebuild, all that happens is they swap the bearings and replace the diode pack, media blast the case and call it rebuilt.

 

Sorry The ECU does control the alternator, diode pack controls voltage?????? NOT the diodes convert the A/C voltage to a usable D/C voltage. The regulator regulates the voltage only what it is commanded thru the instrument cluster which is driven by the pcm. Now you need to check to see if you are getting power to the org/ltBlue wire on alt, it might have shorted and blown fuse. if it has power than your regulator inside the alternator was not designed for your truck. These alternators have looked the same the last 10 years but the regulators are specific to year and vehicle. For example a 2002 alt will bolt up and plug in but won't charge and look the same.

 

The alt. is charging.With the engine off I have 12.9 volts at the battery.When started, it shows 14.5 volts at the battery.The battery light on the dash comes on after the truck is running a few min.I do think it could be the regulater in the alt.The factory alt. was a 130 amp. and I upgraded to a 250 amp. because of Ham radio equipment.It is not a cheap rebuild and the shop is working with me.I was just checking to see if anyone had any ideas . I will check the power on the blue wire when I get home.

 

Want to get pedantic? Fine, we'll get pedantic.

The alternator puts out 3 ph AC voltage to a rectifier assembly (aka diode pack) and from there it goes to the voltage regulator. For the sake of simplicity in assembly, these are normally one black box on the back of the alternator. This is also one of the reasons the alternators are so bloody expensive. Fords used to have separate voltage regulator assemblies remote from the alternator.

The ECU probably has a signal line which taps off the regulated voltage to check and report to the instrument cluster, but unless things have changed radically, the ECU isn't controlling the voltage, it's just monitoring and reporting.

As to having perfect voltage, I can have 14.5 volts but only be supplying 0.1A, in which case nothing is going to charge, hence the recommendation for a charging system check, not just a check with a VOM.