I've been reading through the threads here but still cannot find a solution. I have a 2003 Ranger with the 4.0. I went out to start it and the battery was dead. I put it on the charger and got it started but the charge indicator is sitting on the low side. I check the voltage at the battery and it's only at 11.8V. I had the alternator tested and it failed all tests. I put a new reman in and still not charging. I've gone through all the tests I've read here and everything checks good except I don't have a battery light lit up on the dash. B+ is 12V, yellow is 12V, green is 0V at key off and 12V at key on. The alternator was tested before I left the store. Any thoughts?

 

Welcome to the forum

B+ is battery volts(12v)
Yellow wire is battery volts
Green wire is battery volts(key on)

White jumper wire is plugged in

If above is true and battery volts are not 14volts after start up then alternator is bad, doesn't matter if it was tested, its bad

Charging system is very very simple, no connection to anything else in the vehicle, just has those 3 wires, if they test OK, then alternator is bad

And just FYI, they don't test the built in voltage regulator in parts stores, they just test the rotating part of alternator

 

Thank you for the response. I was using your testing method to figure this out. I'm on the 2nd replacement alternator, both remains and the issue remains. My next step is one from a salvage yard.

 

If its the same brand then yes, go to wrecking yard and get one

As said there is nothing complicated or mysterious about car charging systems, lol

 

Well, went to the salvage yard and got one. I put it in and no change. Oh, but I do have the battery light on now. I'm beyond frustrated with it right now.

 

Then one of your tests wasn't correct

B+ is tested with wire connected, use alternators metal case as the ground for all tests
Yellow and green wire are tested when unplugged

Battery light on with key on means voltage regulator is getting the 12v from green wire

Also the B+ and yellow wire need to be EXACTLY battery voltage, so if battery is 12.5v, then B+ and yellow should be 12.5v, not 12.3v, that would mean a bad connection

Green wire can be 0.1 or 0.2v lower since key is on and other systems draw down voltage

2003 charging diagram below

 

Ok, B+ is at battery 12.04V, I haven't had a chance to give it a full charge. The yellow seems to be a little lower at 11.9. The green is around 11.5. The connector also seems to fit a little loose and I'm wondering if there is a pin fitment issue.

 

And white wire looks OK and plugs in OK

B+ and yellow are both hooked to the same wire, and directly to battery positive, so should be exactly the same, and same as battery
You can put a temporary jumper wire between B+ and yellow with connector plugged in and engine running, and volt meter hooked to battery to see if its starts to charge
One of the fusible links may have a corroded connector

Also wiggle the connector to see if it is loose, you for sure won't get shocked, it only generates 14volts

 

Ron, you are a lifesaver. I pulled the battery out to gain access to the harness. I checked around the crimps for the fusible links and found a hole in the heat shrink. While removing the heat shrink, the fusible link for the yellow wire fell out. The green crusties got it. I spliced in a new section of wire and ran it to the junction box terminals. The alternator charges again! Thank you very much!

 

Good work

Thanks for the update and THE FIX

Very surprising you were getting any voltage on that wire

 

I am too. I was reading 50kohms between the plug and the battery.