New alternator and battery, battery not charging.. - Ranger-Forums - The Ultimate Ford Ranger Resource


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  #1  
Old 02-28-2016
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Icon8 New alternator and battery, battery not charging..

Ok guys, don't let me down. I've been banging my head against a wall for weeks trying to figure this out.

Long story short:

Vehicle: 2001 Ford Ranger 4.0L V6 XLT
Problem: Battery not charging, car sluggish upon acceleration

Quick intro:
1. Driving around and car died on the road. Tested the alternator and it said it was good, battery core was fried so replaced the battery.
2. On the road again, and same thing. This time I replaced both the alternator (from the 95amp to 130amp) and the battery.
3. On the road again, but this time sluggish acceleration, battery slowly draining.
4. Slow charged battery for 24 hrs, cleaned terminals etc. and installed: reads only 12.2V when car is running. I check the draw upon starting: battery drops below 10V. After running for some time with lights on etc. battery reads: 11.86V. So I check the alternator. Ground to B post: 11.86V, positive to B Post: 0.03V, ground to case: 0.65V.

Can someone tell me what is going on?? I haven't gotten the new alternator and battery tested because I made the assumption they were both good from O'Reillys.
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Old 02-28-2016
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Get out the volt meter again.

Yes, on the back of the alternator there is the B+ terminal(big wires and nut) and with key off it should read "battery voltage", if not then fuse/fusible link is blown.

Then there is a 2 or 3 wire connector on the alternator, unhook it.
Yellow wire should also show "battery voltage", if not fuse/fusible link is blown

Light Green wire, should show 0 volts, now turn on the key, this wire should now show "battery voltage", this is the ON/OFF switch for alternator, it is also the Battery Light wire, if battery light hasn't been coming on when you turn on the key then fuse in cab fuse panel is blown, and that's why you are not charging, usually 7.5amp fuse

If these all check out then alternator is bad, doesn't matter if it tests OK, it is bad.
On some there will also be a white jumper wire, it needs to be connected and wire checked, if it is hanging by a thread then fix it

Alternators are very simple devices, the internal voltage regulator feeds the rotor 7volts DC, and the 3 "fields"(in the case) generate AC volts as rotor spins past them
2 diodes on each Field convert AC to DC volts and that is sent to B+
7 Volts in will produce 14volts out, voltage regulator adjusts that 7 volts up and down to keep battery from over or under charging

Yellow wire powers the regulator and is the voltage "monitor", prevents over or under charging

Light Green wire turns off voltage to the Rotor so alternator doesn't drain battery when engine is off, this connection is a "ground" when alternator is not spinning.
This wire goes to one side of Battery Light in the dash, when you turn on the key the other wire on the Battery Light gets 12volts(battery voltage), since Light Green wire is a "ground" Battery Light comes on.
After engine starts(alternator is spinning) the Light Green wire is no longer a "ground" it has same voltage as the wire on the other side of Battery Light, equal voltage means Battery Light goes out, no voltage passing thru the bulbs filament.

An Alternator is basically an electric motor used in reverse, so if you left the power ON it would try to turn the engine via the fan belt, it of course couldn't but would drain the battery trying.


An alternator should produce just under 15volts at battery after starting, then after battery has been recharged from the drain of starter motor, voltage will drop to about 13.6volts, this is called a maintenance charge, it keeps battery charged but won't "cook it", boil off chemicals.
This change in voltage can take a few minutes , depends on the battery, but if it stays high then either battery is bad, or voltage regulator is, if it is the voltage regulator then battery WILL go bad, so you do need to watch for that.

Last edited by RonD; 02-28-2016 at 03:50 PM.
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Old 02-28-2016
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Quote:
Originally Posted by RonD View Post
Get out the volt meter again.
OK

Quote:
Originally Posted by RonD View Post
Yes, on the back of the alternator there is the B+ terminal(big wires and nut) and with key off it should read "battery voltage", if not then fuse/fusible link is blown.
Battery Voltage (POS to NEG, engine OFF): 12.1V
B+ Terminal (to NEG, engine OFF): 12.07V

Does anyone know where the fuse/fusible link is? I've looked around my under-hood fuse box, no large fuses visible..

Quote:
Originally Posted by RonD View Post
Then there is a 2 or 3 wire connector on the alternator, unhook it.
Yellow wire should also show "battery voltage", if not fuse/fusible link is blown
Yellow Wire (to NEG, engine OFF): 10.7V 11.4V
This is a bit jumpy...any ideas?

Quote:
Originally Posted by RonD View Post
Light Green wire, should show 0 volts, now turn on the key, this wire should now show "battery voltage", this is the ON/OFF switch for alternator, it is also the Battery Light wire, if battery light hasn't been coming on when you turn on the key then fuse in cab fuse panel is blown, and that's why you are not charging, usually 7.5amp fuse
Light Green Wire (to NEG, engine OFF): 0.01V

Battery Voltage (POS to NEG, engine ON): 11.8V
Light Green Wire (to NEG, engine ON): 11.71V

Quote:
Originally Posted by RonD View Post
If these all check out then alternator is bad, doesn't matter if it tests OK, it is bad.
I can pick up another alternator if needed, this one has a lifetime warranty.



Also, I thought it was worth mentioning I (accidentally) tested the top of the radiator to the NEG terminal and it showed -0.4V, what would this mean?

Thanks for all the help RON!!
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Old 02-28-2016
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The Fusible links for charging system all show they come from Battery Junction box.

Was the White wire OK?
Looks good

Yellow wire is troublesome, that is almost a 2 volt drop, thru a direct connection to battery.

On my 2001 diagram it show 2 fusible links(both Grey) in parallel for B+ wire(Black/orange wire)
And 1 fusible link(Brown) for the Yellow wire, but this is connected to B+ wire.

So B+ and Yellow wire should read exactly the same voltage at the alternator.

With meter connected to Yellow wire(disconnected from alternator) try moving the wiring harness around to see if you can find the bad connection.

Diagram here: | Repair Guides | Charging System (2001) | Charging System (2001) | AutoZone.com

Last edited by RonD; 02-29-2016 at 10:16 AM.
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Old 02-29-2016
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Thanks for the diagram and info. I'll have to do some research and some more poking around. Does anyone have a video of how to move/remove the wiring harness for diagnostics?
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Old 03-25-2016
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Ok, so I tested a bit more (now that the weather is better), and came up with the following:

Battery Voltage (POS to NEG, engine OFF): 12.12V
Battery Voltage (POS to NEG, engine ON): 11.87V
B+ Terminal (to NEG, engine ON): 11.79V
Yellow Wire (to NEG, engine ON): 11.79V
White Wire (to NEG, engine ON): 0.09V

I replaced the "Left stop/turn trailer tow connector" fuse #7 at 7.5A as that was blown, though I don't think it's related. The battery light on the dash is on.

I moved the wiring harness around to see if there was any bad connection, and didn't find any yet. Same thing with the fusible links. Everything seems to check out.

THOUGHTS??!?!?

Last edited by diverman241; 03-25-2016 at 08:01 PM.
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Old 03-25-2016
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For sure the alternator is not putting out any power

Light green wire on 3 wire connector
Unplug connector
engine OFF, key ON

Red volt meter probe to Green wire, black probe to Ground(battery "-")
Needs to show 12.12v, or same as battery

If not fuse is blown in cab fuse box, usually 7.5 amp

All alternator voltages are tested with engine OFF, Key OFF except for this one wire.
Only voltage tested with engine running is battery voltage, over 13.5volts means alternator is working, under 13.5volts means it's not, so 11.79v is a not working

Take alternator back if possible.
new battery is also drained, should be 12.7v or higher
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Old 03-25-2016
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Ok,

Battery Voltage (POS to NEG, engine OFF, key ON): 11.98V
Light Green Wire (to NEG, engine OFF, key ON): 11.84V

All fuses (in cab and under hood) have been tested and the one mentioned above was replaced.
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  #9  
Old 03-26-2016
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I took the alternator back, they tested it (fail) and the others they had in stock (fails), apparently they had a bad batch. Gave me remanufactured one that passed.

HOWEVER

Battery charged back to 12.7V
After install:
Battery Voltage (POS to NEG, engine ON): 11.79V

WTF!?!
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Old 03-26-2016
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Can you get your money back, this place is causing you a lot of wasted time and effort.
"We must have got a bad batch", now that's a WTF!

Charging systems are just not that complicated
You tested all the wires and they are good, so alternator is bad, not complicated at all
Maybe "bad" alternator blew a fuse..........
If you want to test wires again then do that:
engine OFF, key OFF
B+ wire = battery voltage
3 wire connector unplugged
yellow wire = battery voltage

Key ON, engine off
Green wire = battery voltage

If wires pass the test then plug connector back in and start engine
Battery voltage above 13.5v all is well
Battery voltage below 13.5v alternator is bad

Read here: Ford Ranger Alternators

get one from a wrecking yard, plug n' play
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