Alternator or VR issue?
So got back to this during the weekend.. ran new wire for field and jumped from VR ign to new VR FLD and get less than 12 at the alt field and nothing more than 12.3 at alt post even with increasing RPM.
GO READ POST NUMBER TWO!!!!
Now, let's keep it SIMPLE.
"Got a VR". WHAT does that mean? Did you get a 69/ earlier VR or a 70/ later VR?
Have you CHECKED that the alternator FIELD is drawing current? Get into the service manual, and there is a procedure to measure the field current, so along that lines, ...................
Check field continuity, jumper power into the field and be sure it is drawing current.
When I say JUMPER I do NOT mean to use ANY PART of the factory wiring!!!! I mean GROUND the field if it is isolated, and FEED 12V into it with a jumper wire.
IF IT WILL NOT CHARGE under that condition, MEASURE the output voltage RIGHT AT the alternator output post, WHY?? Because there could be a problem in the charge wire wiring on the path to the battery. And that has HAPPENED!!!
You MUST get this done FIRST so you can eliminate some items.
IF THAT WORKS, now re--connect the harness to the alternator and again, find out if you have any power going to the field (key on) and is there any actual current being drawn? If so, repeat the test.
On the older alternators you can easily jumper the two VR wires together and this JUMPERS full battery into the field which tests all I have said above, plus proves whether the factory harness is "good" and providing 12V to the field. THEN you can worry about the VR
THIS IS NOT THAT COMPLICATED NOR DIFFICULT, a little "simple thinking:"
You have basically TWO electrical circuits (69/ earlier circuit)
You have the ALTERNATOR OUTPUT. This (originally) goes from the alternator output stud, through the bulkhead (large black) to the big welded splice under the dash---to and through the ammeter (big black) out of the alternator (big red)...back out thorugh the bulkhead, through the fuse link, and to the starter relay stud, and to the battery
FIELD VR: For 69/ earlier, one end of the field should be GROUND. The single field wire (green) goes to the VR which MUST be grounded, to the IGN terminal, and this is 12V coming from the keyswitch "run" IGN1 circuit.
DIFFERENCE with 70/ later. EASY
Like the 69, you have switched 12V feeding the ign terminal of the VR WHICH must be grounded, out the GREEN field terminal and to one of the two field terminals on the (70 and later) alternator. The remaining field terminal gets switched 12V also from the igntiion "run" circuit, and is blue. The VR controls the "amount of ground" shall we say, to the field circuit, to control output
SO YOU MUST
1....Test and figure if the output circuit is OK
2....Test and decide if the field circuit is OK
3.....Test the alternator by "full fielding" it thus leaving the VR out
4....If all the above is good, and you can find no other, replace the VR.
5...In some cases a sulfated battery can cause issues, but will NEVER cause a "no charge" condition.
