lewis712

Yesterday I put in a new 850 cca battery along with a re-manufactured alternator from Advance Auto. Today, I went to Advance Auto and had them test things to make sure everything was working properly. Here are the results:

Good Battery:
Voltage: 12.56V
Measured: 987 CCA
Rated: 850 CCA
Temperature: 71 degrees

Starter Test:
Voltage: 11.26V
Amps: 0.0A
Time: 812ms
Cranking - Normal

Charging System Test: Results - No Problem
NoLoad: 13.32V
Loaded: 13.24v
Ripple: 44mV

Everything tested out normal. However, my battery light is still on. I read on a few posts about fuses, but I am unable to find anything. Maybe someone can point me in the right direction.

I have a 2005 Ford F150 FX4 supercrew, 5.4 engine.

Thanks,
Andy

firehart2

Did you use an aftermarket alternator? If so, the regulator/ brush assemblies in them are known to cause the battery light to come on. I commonly rebrush factory regulators and this keeps the problem at bay.

lewis712

I purchased one from Advanced Auto Parts. This is the one i bought.

How do I go about rebrushing the regulators? Can I do that with it installed?

Thanks,
Andy

homer

You'll have a lot of people stating to go with the OEM alternator. Part of the issue (I have other posts about it here) is that the newer alternators are smart alternators. The PCM commands how much it wants the alternator to generate based on load it detects unlike you're traditional alternator.

lewis712

So do I need to go to the dealer to have the program the PCM? Or do I just let the battery light go?

homer

https://www.f150forum.com/f4/battery...2/#post4182854

homer

No... bring the alternator back and try another or bring it back and go to an OEM. Programming the PCM won't help...


And sometimes you can still measure 13.5-14.5 volts at the battery and it charges, but the light stays on.

Quite often what the issue is, they rebuild the alternator (new brushes and bearings) but often it's the controller in the alternator that's actually the issue. Many bench-tests can test this very well so they re-sell the alternator as remanufactured but it's faulty. So you can bring it back and try another and you might get lucky, or just bring it back and get an OEM (although I realize the cost is quite high). If you search for alternator on here, you'll see how many people had issues with reman'd ones.

techrep

iTrader: (1)

You need to return the Alt from Advanced and go get a Motorcraft Alt.

lewis712

I had a guy who rebuilds altenators tell me that if I turn the ignition on and pull out the 3 prong plug on the alternator, that the battery light should go out...which means the alternator is bad. If the battery light stays on, that mean something other than the alternator is bad. I was told there could be fuses in the wires between the battery and the alternator. I guess I'll check those next and then maybe the fuses as well.

homer

I did this on a Ford Focus as well (never tried on F150). On the Focus, it has the "Smart charge plug". If you unplug it, it turns the alternator into a traditional style... it runs as an older alternator ignoring control from the PCM. It was interesting because on the Focus, the battery light wasn't on when the alternator was dead.... unplugging the connector made it light up. In either case, it was only reading battery voltage, no charging. So I do believe this method works.


I'm assuming the alternator in this case is working but it's not satisfying the PCM (i.e. bad circuitry). We weren't told if they're getting 13.5-14.5 volts or not though.