1994 Ford Ranger Alternator Charging Issue

[Wayne Ward]

Currently I am getting between 14.3 and 13.3 coming from the alternator while driving. (I have a digital monitor in a USB charging device that I installed in place of the lighter) It drops with accessories on of course BUT it is not at 14.3 when everything is off all the time. Sometimes it drops into the 12v range. Very inconsistent and wondering if it could be the connector circled in the picture below. It is very loose. I did not see a new one available on rock auto. Any recommendations as to where I can get a new one? Other suggestions for the voltage drop would be great too.

 

[RonD]

Probably not the issue but unplug it, then use a small screw driver on the metal slot in the connector to bend it, so it clamps the metal tab in alternator better
On Fords it is usually a white wire, its called the Stator wire

What you describe is most likely a failing Field coil, and Stator is part of that section of an alternator
Alternators case has 3 Fields(coils of wires), the spinning rotor generates AC volts in each coil, AC volts are converted to DC by diodes

Because an electrical "circuit" needs 2 wires to complete the "circuit"(circle), think of the Stator as the Neutral wire in an AC circuit
And like in your house wiring Neutral is also connected to Ground in your house panel
The Stator is connected to all 3 Field coils, the OTHER wire from each Field coil goes to the diodes to make DC out voltage
Stator voltage is only present when alternator is spinning and lower voltage than alternators DC output
Stator voltage was using for electric choke heaters in the good old day, because it only had voltage with engine running and lower voltage allow longer warm up for choke heater so slower opening time


Sign of a failing Field is dimming lights at idle OR if monitoring voltage while driving a drop in voltage without associated power draw, like fan turned to HIGH should show a drop but then a return to previous voltage level, thats the voltage regulator working correctly
If voltage just drops and doesn't come back up, thats usually a Field issue
13.5v is usually about the lowest it should be at warm idle, lowest RPM
13.3v is fine, anything in 12v range is not

 

[Wayne Ward]

So is it time for a new alternator? Rebuilt or new if available? I would like to keep her stock of course as I am not running a winch or a ton of extras.

 

[RonD]

Yes, from your description a new or rebuilt alternator would be a good idea, before it fails outright

 

[Wayne Ward]

Is motorcraft OEM for this or are there others. Rockauto has a Motorcraft for 162 with CC of $15us.

 

[RonD]

Motorcraft is the Ford brand so yes, its OEM

 

[4x4prepper]

> I have a digital monitor in a USB charging device that I installed in place of the lighter

It probably is the alternator or wire coming loose, but, considering the cost of an alternator ...

I would verify the state of charge under the hood with a DMM.

Belt tension matters, especially with a serpentine belt system, it can change if the tensioner is bad.

I would make sure the wires/plug for the (internal) voltage regulator have continuity since it looks like a sharp bend in the picture. Looks like a new harness connector is $17 from Advance. The green with black stripe might be fatigued, that would be the one I would wiggle while checking continuity.