Battery Light Intermittent On/Off

[dhanni848]

I know there are many other threads on this, but not sure where to go from here as I have read almost all of them.

Last week replaced alternator after battery light came on and heard the alternator whine and smell. Replaced with refurbed 200amp from O'Reilly as that is what they had and headed out of town. Battery light comes back on over the weekend, and then dead yesterday morning. Replace battery as it was sitting at 10V.

Ran great for a day, and this morning on then off, on then off. Checked the battery and it is at 13.5 sitting and running is at 14.3.

I have had no issues until the alternator crapped out. Now I cant get it figured out. Is the O'Reilly alternator just not cut out for our trucks? I have done nothing else to it since foglights and a light bar 2 years ago.

 

[W0n70n]

The O'Reilly, autozone, advanced etc alternators will pass bench tests but fail because the Battery Management System can't control them correctly so they will fail. I suggest getting OEM or a reputable upgrade like Mechman. It sucks but it's the only way I was able to fix it after months of troubleshooting.

 

[MurderedOutSVT]

The O'Reilly, autozone, advanced etc alternators will pass bench tests but fail because the Battery Management System can't control them correctly so they will fail. I suggest getting OEM or a reputable upgrade like Mechman. It sucks but it's the only way I was able to fix it after months of troubleshooting.

Yep, those pass bench tests great but thats about it

 

[dhanni848]

That is the only idea I had left since I know nothing else has happened. I will have to see if they will refund me and order the Motorcraft one.

I had them check it before I left the store, but I guess as you both said...just not good equipment.

 

[W0n70n]

The alternator will technically output the rated amperage and generate a voltage that is within spec but it won't do it when the ECU goes to tell it what to do. I didn't have an issue with my local O'Reilly taking back their defective alternator when I explained the issue to them. Motorcraft replacements aren't normally that hard to find but make sure you also check the resistance of the primary charge wire (big red one with the black box on it) to make sure the in-line fuse is intact and didn't get damaged when the old generator died.

 

[dhanni848]

Thank you, and guy i worked with there was nice. The first one they gave me had a back voltage regulator. What should that wire read?

 

[W0n70n]

Thank you, and guy i worked with there was nice. The first one they gave me had a back voltage regulator. What should that wire read?

Effectively Zero or extremely low resistance, just to make sure the large ceramic fuse is intact and not creating a resistive load from being "burned" by the old alternator.

 

[dhanni848]

Went back to O'Reilly yesterday and they price matched RockAuto . Was listed at $839 and matched down to $369! Hope to have it tomorrow. Fuse seems to be good.

 

[dhanni848]

No issues so far after installing Motorcraft alternator.

 

[W0n70n]

Good to hear, I don't know what it is about the autoparts alternators for fords but they're pretty much 100% defective.