The truck's idle, headlights, and all other electronics consistently pulse and sort of start "bobbing" when i idle or stop in gear. It still does this with a consistent 14.7 voltage at idle.
Voltage drops down to 13s for a moment whenever the thermostat or heater core opens when i'm at a stop. The motor hesitates along with it.

I used a multimeter to check various things:

• Alt~14.7 volts
• Battery tested fine (tossed in spare to make sure, no effect)
• Grounds are all visibly connected well, and they're all tight
• Battery terminals have good connection
• Fuses are all good

I need advice from someone who has more experience.
There are no driveability issues related; no lights, codes, or non-OEM parts or wiring.
The idle just sounds like its surging/hesitating a little and the lights dim and pulse along with that.
Still a bad ground somewhere?

(2000 f-150, 4.6 rwd auto)

 

Did you actually get the alternator tested?

 

The alternator has a voltage regulator attached to it that is supposed to control the voltage.
Obviously it is not working if you see that much brightness and voltage change and know it's not correct...
14.7 is too high and cooks the battery electrolyte out.
A good battery fully charged will show running system voltage about 14.1 +/- a tenth on an accurate meter.
Replace the alternator.
Raise a hand and point one finger toward head!
Good luck.

 

Put the finger back in its holster.

The allowable charging voltage, per the factory service manual, is 13-15 volts. His alternator is NOT overcharging.

The problem he is having is due to the alternator "hunting" for the proper output voltage and it's causing a pulsating effect that's visible in the lights. This is usually due to excessive resistance in the "A" (battery sense) circuit. The "A" is the OR/LB wire that comes off the alternator, goes back through fuse F11 in the BJB, then via a red wire back to the "hot" stud on the starter relay (which connects to the alternator output.

 

I just woke up, and actually laughed out loud when i read "put the finger back in its holster." Thanks for making my day hahha.

I will check my resistances in the "battery sense" loop later on. Thanks for the input and the laugh!

 

Make sure that you 1) disconnect the battery first to avoid meter damage and 2) use your lowest ohmmeter range and "zero" the meter first so you know what the "excessive" resistance actually measures.

There are several points in connectors and the fuse/fusebox where a little bit of corrosion might have occurred that could cause the concern.

This is a known issue on the Conturd/Mystake electrical systems (which I've worked on for about 15 years) and one that Ford actually issued a TSB to re-wire the A circuit to eliminate the issue on those models. I don't think it's be a common problem on the trucks although I've seen a few posts/threads regarding it over the years. I don't recall if any of those posters ever followed up, though, so I don't have any feedback.

You could also make a jumper with a 10A fuse in it to connect the A terminal to the B+ connection and see if the pulsing stops. No need to disconnect anything else or get out a meter.