Lights flickering

[rtbrjason]

I'll look at the wiring diagram later tonight to find the color code for the sense wire. As a test it would be interesting to see if a straight shot from the battery to the sense and another to alt case ground has an effect on the wave form.
A good wave form looks like continuous string of lower case "m".
It would also help to know the high and low voltage reading on the scope. Even though a dmm shows 14.3 volts it may not respond fast enough for the spike to register.

I never really got anywhere with this and am still having this issue.

It does appear to be an alternator issue. With the alternator disconnected from the battery, the flickering goes away. As soon as I touch the alternator main wire to the battery +, it starts flickering.

Not sure what else to do since all 3 alternators have had this behavior and all signs point to it being the alternator.

I do have a ridiculously oversized ground running from the alternator straight to battery. The rest of the "Big 4" grounds are also done. I tried with an without a secondary 0 awg charge wire from the alternator. I replaced the short run of the other 2 wires that run to the alternator as well.

 

[z168]

That is annoying. Hope you get it sorted out. Battery-alternator-grounding, those are the only ones and looks like you got it covered

Looks like the 150s arent immune to this issue either → F150 forums

 

[stamp11127]

Seems to be a common problem on Ford trucks. Solutions have been changing the mfs, replacing shorted abs sensors, cleaning connections, tracing the charging circuit wiring.
I suggest going back over the connections making sure they are clean especially the alt output cable /mega fuse if it is in the circuit.

 

[rtbrjason]

I did end up going through what I think is/was every similar thread I could find on Ford Trucks. I've replaced the ABS sensor while trying to fix a flashing 4x4 light (this is still an issue as well), and replaced the main light switch since I had done the fog hack on my original switch. When I read that someone else had this issue and it was the fusible link, I bypassed it completely with a new 0 gauge power wire. As soon as I pull that wire off the battery, it stops flickering. I've also replaced almost all the bulbs with LEDS. All the sockets and everything were pretty clean.

I'm thinking of trying a new start solenoid since all the power wires go through there, but since the flickering goes away as soon as the alt main charge wire is removed, I'm not sure it's worth throwing money at more parts..

 

[stamp11127]

You may try pulling & reinstalling each fuse while running to locate the circuit it is on. The only fuses you would leave are for the pcm and fuel pump.

 

[rtbrjason]

You may try pulling & reinstalling each fuse while running to locate the circuit it is on. The only fuses you would leave are for the pcm and fuel pump.

That's a great idea. I will give it a shot and report back.

 

[stamp11127]

If the result is that it isn't any of the circuits you checked then the fuel pump, pcm circuits, main bus and grounds are what is left. Ir will be one one or more of them.
Since you are in a salty road state I would go over the grounds again plus do a voltage drop test on each connection/leg.

 

[rtbrjason]

If the result is that it isn't any of the circuits you checked then the fuel pump, pcm circuits, main bus and grounds are what is left. Ir will be one one or more of them.
Since you are in a salty road state I would go over the grounds again plus do a voltage drop test on each connection/leg.

I've finally had some time to go through the fuse exercise today. I found that the only fuse that stopped the flickering completely without causing it to stall was fuse number 11. That's the charging circuit though so I guess that was to be expected?

 

[stamp11127]

If you have a set of jumper cables, clamp one of the negative alligator clamps on the negative battery post and the other negative clamp on any metal part of the engine so that it will not get caught by the belt/fan. Crank and run the engine to see if the flickering stops. This is assuming the terminal has a clean connection to the battery post.

Your symptoms are pointing to a poor connection somewhere in the charging system.

 

[rtbrjason]

If you have a set of jumper cables, clamp one of the negative alligator clamps on the negative battery post and the other negative clamp on any metal part of the engine so that it will not get caught by the belt/fan. Crank and run the engine to see if the flickering stops. This is assuming the terminal has a clean connection to the battery post.

Your symptoms are pointing to a poor connection somewhere in the charging system.

I can try that, but I have a fairly ridiculous amount of grounds coming off the battery. Going to the body, alternator body, frame etc all 0 AWG wire. The battery and battery terminals were recently changed as well. The starter was recently out and that ground was cleaned up as well.