Ranger (2002 V6 4.0 SuperCab) Battery Gage Went down/up

You really should perform proper diagnostics instead of just throwing parts at it. First test: get an ODBII scan tool and see if there are any stored codes (bet there will be one or two).

Then run diagnostics on the charging system.

Thanks, I think PepBoys runs free scans.

Bill

You are close.

The regulator is built into the alternator, and I think you need a new one. You may only need new brushes, but You pretty much have to pull the alternator to find this out. Once the alternator is out on your bench -- an easy job -- then you can pull the brush pack with a screw or two. You should turn the alternator pulley by hand (slowly) and inspect the armature/stator (depending on how anal you are about the distinction) for damage -- knicks and such -- that can damage the brushes.

I'm not sure, but I _think_ your Ranger takes an alternator that has the brushes available for under $20. I put brushes into my F150's alternator, but did not look at the armature/stator, and missed the knicks that ate the crap out of the new brushes in about 6 months. I had to buy a new alternator, but if the brushes had worked, I could have fixed my problem for $20 instead of $150.

Does the Charging System store OBD II Codes? I'm not aware of any codes for the charging system. There is a code for the ECM being disconnected, but not for underperformance of the charging system.

Depends on the design... Some (many?) alternators today the regulator is part of the ECM. As well, the ECM will monitor and set codes for 'low battery voltage', and maybe some freeze frame data too. Since getting codes is easy, that is one step that should always be done.

Definately for underperformance of the entire electrical system, and for some vehicles with an ECM based regulator you get much more. They can be maker specific codes however.

If this is an alternator with a built-in regulator, I agree 100%. As well, it is not necesasry to replace the regulator if it has not failed. Brushes, when they get worn, tend to stick (the spring tension is less due to their shorter length, and aging of the springs) which leads to problems similar to yours.