2000 Ranger 4.0 not charging after new alternator

[JoeSwar123]

Good evening, just installed a 130 amp alternator on ford ranger. Will not charge battery and have checked what I believe to be the proper fuses. Can confirm we are getting voltage to plug when disconnected from alternator. Any wisdom or guidance is appreciated

 

[RonD]

Welcome to TRS

Key off
Use volt meter or test light

Use alternator's metal case as the ground for all tests
Put volt meter on B+ terminal, the stud/nut terminal on the back of alternator
Should see 12volts, if not MEGA 175amp fuse on outside of engine fuse box is blown
Replace it before any more tests

Unplug the 3 wire connector on alternator
Test Yellow wire
Should see 12volts, if not 30amp ALT SYS fuse in engine fuse box is blown

Test light green wire
Should see 0 volts
Turn on the key
Should now see 12volts, if not CAB FUSE BOX fuse 15(7.5amp) is blown

No test for white wire but make sure it got plugged in correctly to it's single spade terminal on alternator

If all wires test OK then plug back in 3 wire connector and start engine
Battery should show 13.5volts to 14.8volts, if not the new alternator is bad, period
Charging system is very very easy to test, just 3 wires, no mystery

Alternators on the other hand can not be tested, well at least by any auto parts store I have ever been to, they either work in your vehicle or they don't
I have read recent posts of people having to return 2 or 3 new alternators to get a working one, I would change brands after the first bad one out of the box, lol

 

[Lefty]

Welcome to TRS

Key off
Use volt meter or test light

Use alternator's metal case as the ground for all tests
Put volt meter on B+ terminal, the stud/nut terminal on the back of alternator
Should see 12volts, if not MEGA 175amp fuse on outside of engine fuse box is blown
Replace it before any more tests

Unplug the 3 wire connector on alternator
Test Yellow wire
Should see 12volts, if not 30amp ALT SYS fuse in engine fuse box is blown

Test light green wire
Should see 0 volts
Turn on the key
Should now see 12volts, if not CAB FUSE BOX fuse 15(7.5amp) is blown

No test for white wire but make sure it got plugged in correctly to it single spade terminal on alternator

If all wires test OK then plug back in 3 wire connector and start engine
Battery should show 13.5volts to 14.8volts, if not the new alternator is bad, period
Charging system is very very easy to test, just 3 wires, no mystery

Alternators on the other hand can not be tested, well at least by any auto parts store I have ever been to, they either work in your vehicle or they don't
I have read recent posts of people havng to return 2 or 3 new alternators to get a working one, I would change brands after the first bad one out of the box, lol

I had the very same problem with a new alternator. I brought it back. They tested it, confirmed that it was not working, and gave me another. Sometimes too, a battery can be so drained that it will not charge or charge well. If so, a gas station will slow charge it.

 

[ekrampitzjr]

130 amps is an aftermarket high-output alternator. The factory alternator had a rating of around 105 amps. At least for mine, new (yes, new, not reman) Motorcraft OEM units are still available, and I have one on standby.

Worst case is that you need to revert to the factory spec because something might not be compatible somewhere. That might not be necessary, but I agree that the alternator you installed is suspect.

 

[RonD]

Rangers/B-series and Explorers did have an "option" for 130amp factory alternator from 1998 and up

 

[ekrampitzjr]

Rangers/B-series and Explorers did have an "option" for 130amp factory alternator from 1998 and up

Didn't know this. The factory version might not be available now, because no Motorcraft or Ford 130–amp alternator came up when I was shopping for the one I got.

Some of the aftermarket stuff claims crazy amperage ratings well above 130.

 

[RonD]

Alternator amp ratings are also when engine RPMs are at 2,000 and up
At idle, under 1,000rpm they have about 60% of the amp rating

So 100amp alternator can make about 60amps at idle(700rpm) which is fine since most vehicles only need about 45amps with all the electrics on and engine running

Alternators have 3 Fields that generate AC voltage, 1 Field failing is common in older alternators, so you lose 1/3 of the available amps
Most notice this first with lights dimming at idle because 45amps needed is now marginal, when RPMs go up then lights are back to normal

Vehicles with heated seats, rear window defroster, premium sound systems often used 130amp alternators, more common in Explorers than Ranger though

 

[Lefty]

Ask the auto parts dealer if you can have the old 105 amp alternator with the uprated voltage regulator.