Alternator question., Not Charging. Options

[Olympic 914]

Took the car out for a drive today, planning on going to dinner. everything is working as it should. getting on the PA turnpike and I had to accelerate briskly to get into traffic, and a moment later I noticed that the RED alternator light had come on. Pulled of at a wide spot to check the belt and wires and shut it off. Not checking the belt with it running. Belt good, plug tight, tapped the VR a couple times for good measure and started it back up. Light still on and now my Autometer AFR gauge just had bars. I know that is because it doesn't turn on until the voltage is +13v So not charging.

Now I am on a limited access highway with the next exit `12-15 miles away. Good thing had the battery fully charged on the tender before I left the house. So I made it to the next exit, turned around and headed back home for a total of 35 miles on battery only. Whew. But that shot dinner.....



Replace the VR with another I had that previously tested good. still no charging. checked the plug on the relay plate again. looks good.

I have not yet checked the wire connections at the alternator, possibly a wire vibrated loose during the brisk acceleration.

Now the question

I read to test the VR to short between D+ and DF and if the alternator is good voltage at the battery will go to alternator maximum of about 15-16V

So do I REMOVE the VR for this test? and jump between the D+ and DF at the relay plate.
OR
Leave the VR in place and short between those pins?

[Spoke]

Did you do the test with the 1156 bulb across the GEN light or across battery to D+? If so, what happened?

[Gatornapper]

Yes. Nothing happened. Did not energize the armature, no charging, light went on and stayed on - just like GEN light......

As wattage of bulb was more than 2 watts, the filament being a lower resistance, the voltage hitting the armature would have been higher than that of the 2 watt Gen bulb - and the armature should have been excited and produced a charge.

HOWEVER, remember - when I hit DF with a full 12 volts - the system charges to a full 14.1 volts as it should........but as soon as you remove the external 12v to DF, the charging ceases. Once energized, the armature should stay excited, producing a charge.

So I'm thinking the problem is in the armature.....perhaps a break in insulation that allows leakage of the voltage. I.e., a short.

GN

Did you do the test with the 1156 bulb across the GEN light or across battery to D+? If so, what happened?

[Spoke]

Yes. Nothing happened. Did not energize the armature, no charging, light went on and stayed on - just like GEN light......

OK, so a higher power GEN light doesn't get the VR started...

As wattage of bulb was more than 2 watts, the filament being a lower resistance, the voltage hitting the armature would have been higher than that of the 2 watt Gen bulb - and the armature should have been excited and produced a charge.

You applied the 1156 from 12V battery to D+, not to DF. DF energized is the responsibility of the VR. If the VR is not working, applying 12V to D+ will not energize DF.

HOWEVER, remember - when I hit DF with a full 12 volts - the system charges to a full 14.1 volts as it should........but as soon as you remove the external 12v to DF, the charging ceases. Once energized, the armature should stay excited, producing a charge.

Did you do this with the VR in place? Once you remove 12V from DF, if the VR is not operating, the voltage at DF could go to zero and the alternator will not function.

So I'm thinking the problem is in the armature.....perhaps a break in insulation that allows leakage of the voltage. I.e., a short.

GN

Your previous test seems in conflict with a bad armature as you were able to get 17V at the battery with the armature initially being driven with the GEN light:

DID THE D+ TO DF Jumper TEST: at rpm, voltage at battery jumps to 16.9 to over 17.

It still seems like the VR is not starting up. I would be curious to know the voltages at the VR when running. The VR I have on my 914 has a plug and wires connecting to the VR thus I can measure voltages right on the VR plug. They should be the same as the voltages on the alternator plug.

Here's another test: With VR in place, start engine then short DF to D+ with the 1156 bulb. What you'd be doing is simulating the VR pulling up on DF as it should but seems it isn't. If the battery voltage goes up, then the alternator should be good.