So i bought a 2011 ford ranger with a 2.3. Battery light was on when I bought it. Runs fine, I've had no issues until after a month or so i noticed my lights dimming sporadically. I had the battery and alternator checked. Advanced told me my alt was reading high (15+ volts) and that the battery was on it's way out. I replaced both. The alternator was a remanufactured from advanced. Battery light never went off, issues persisted, and are now worse. I have warrantied out the alt so I know it's not that. I have checked the wire from the battery all the way to the alt. Nothing looks damaged, frayed, or burnt. The ground to the fire wall from the back of the block i have moved to a more direct connection to the firewall. My lights surge and dimm. My gauge cluster will go out if I'm driving at a higher speeds and the rpm stay high. The ac blower speeds up and slow down with the rpm and the passenger air bag light will come in and off at odd times with the lights surging. I'm lost....

 

You need a Volt Meter

Test battery voltage first, remember it, new battery should be 12.8 volts or so

Alternator has 3 wires connected
Unplug the 2 wire connector
Test the red wire, should show Battery Voltage, exactly, if not you have a bad Fusible link

Test the bigger red wire on back or side of alternator, no need to disconnected it, should show Battery Voltage, if not a Fusible link is bad

Test Grey wire on 2 wire connector, should be 0 volts
Turn key on, and test again, should be Battery Volts, less .2v is OK, so 12.6v, this is the Battery Light wire

2011 may have "smart charging" this should be turned OFF by a Ford dealer as soon as possible, call dealer with your VIN and see if it may have that and how much to shut it OFF, it never worked well

If all test OK truck wiring is GOOD
Plug alternator back in

Start engine
Test battery voltage again
Should be 14.3-14.8 volts, NO HIGHER, system voltage should NEVER go above 15volts, that will kill the battery
Drive truck for 10 minutes, or longer, is fine, don't shut it off!!
Open hood and test battery voltage again, should be 13.5-13.8volts, NO HIGHER
And never lower than 13.5v when engine is running, that will drain the battery

 

So I checked battery. 12.9. Checked the red wire and it was 0. I checked black 0. I think my probe isn't getting into the plug to get a connection honestly. The big red wire was 12.9 on the nose.

 

Then use a paper clip into the connector and test it
If Red is still 0 then you have a blown fusible link, and alternator won't work

Do the same for the black(grey) wire, 0 volt key OFF, 12.9v key ON

 

Used a paper clip, still got 0 on the red wire. The black wire read weird. It was never a constant reading. 12 volts then down to .5 then up above 12. Not sure if I'm doing something wrong or what. My meter was set to read DC, I tried getting a ground in multiple places ( frame, side of alternator, and on a bolt holding suspension to the frame) and still had the same results.

If the red wire is 0 and that's a bad fusible link, where do I go to find that link?

 

The grey or black wire pulsing Voltage, WHEN key is on, should be OK, you have Smart Charging, so computer in the cluster cycles charging on and off I would expect

Don't know where Fusible link will be exactly because Ford moves them around

Should be close to the engine fuse box, you will need to follow the larger and smaller Red wires from alternator to engine Fuse box

Near the fuse box you will need to open up the wiring harness, the fusible links will be in the harness

A fusible link looks like a wire, it may or may not have a tag on it, like this: https://www.freeautomechanic.com/mec...ks-300x181.jpg

Or this: https://www.ford-trucks.com/forums/a...1&d=1341705636

Or this: https://i.ebayimg.com/images/g/sPYAA...hIm/s-l300.jpg

You alternator uses TWO of these, diagram below