Alternator question., Not Charging. Options

[Spoke]

I have another idea: I'll bring a 1 amp fused 12+ from the battery through an 1156 bulb to D+ on the alternator plug terminal.

About the 1156 bulb with 1A fuse; the 1156 bulb will be the fuse and the load. The 1A fuse isn't needed as the 1156 bulb when put across 12V will burn about 2A.

Waiting to see what happens with this test. This will see if the alternator/VR will start up with significantly more current via the 1156. If the alternator/VR does start up, then the 1156 bulb will go out. If the alternator/VR does not start up, then the 1156 bulb will continue to light.

[Gatornapper]

I would say yes.

But remember, it puts out full voltage and more when D+ & DF are jumped - on that harness......if the harness were bad, I don't think you'd see that.

Somehow the armature is not getting excited.

GN

I would say the Bosch ones are ok. Is the alternator harness the original?

[Gatornapper]

I have another idea: I'll bring a 1 amp fused 12+ from the battery through an 1156 bulb to D+ on the alternator plug terminal.

About the 1156 bulb with 1A fuse; the 1156 bulb will be the fuse and the load. The 1A fuse isn't needed as the 1156 bulb when put across 12V will burn about 2A. I thought of that myself after I suggested the setup - no need for 2 fuses....been very busy, will try tonight.....

Waiting to see what happens with this test. This will see if the alternator/VR will start up with significantly more current via the 1156. If the alternator/VR does start up, then the 1156 bulb will go out. If the alternator/VR does not start up, then the 1156 bulb will continue to light. Yup! Exactly. It will function as the GEN light......

Also doing this from Pelican's site: To trouble-shoot the problem, you need to check the various sections independently. Thus the first check: Connect +12 volts from the battery to the DF terminal on the relay board. This is the maximum field current situation, and should result in maximum output of the alternator. Note that this checks the B+ diodes, the alternator windings, and the common diodes. It does NOT check the D+ diodes.

But, essentially, this is duplicating the test with the 1156, and just energizing the armature from another route - directly on the DF wire instead of through the switch in the VR......

GN

[Gatornapper]

Post I just made on Pelican's forum:

Greg -

Did your test. Plugged VR directly into alternator harness. Hit D+ with other side of lamp with 12+ on the opposite side. Lamp lit up - just like dash light - as it took the place of the dash GEN light in the circuit. Still no charging. 12.2 v at battery.

So clearly something is wrong, and it's not in the relay board or dash light circuit.

AND YET, using the 2 tests in this Pelican article,

https://www.pelicanparts.com/techarticles/9...roubleshoot.htm

The alternator checks out fine.

Test 1 "checks the B+ diodes, the alternator windings, and the common diodes. It does NOT test the D+ diodes". I hit DF with 12+ volts, and the system charged at full normal voltage: 14.1 volts.

But as soon as I removed the 12+ v from DF, the charging ceased. Once the armature is energized, shouldn't it stay energized?

Test 2, we know, tests the D+ diodes and "D+ portion of the system", by jumping D+ and DF - my system also passed this, producing 17+ v at the battery.

So what part of the system is failing? I can't see how it is the harness - as in both tests 1 and 2 full charging voltage is being produced at the battery....using the existing harness.

Seems to me the problem is indeed inside the alternator - as it will not retain its charge on the armature once charged. Something is preventing the armature from retaining its charge......all other things seem working properly.

Any insight and wisdom is greatly appreciated.

GN

[ClayPerrine]

You can't use just any light for the alternator light. It has to be a particular bulb to make the circuit work.

If you can connect DF to the positive battery post with the engine running, and get 17+ volts, then the alternator and harness is good. I would change the voltage regulator. Get a Bosch regulator, not some aftermarked reproduction.

[Gatornapper]

Clay -

The 2nd VR I tried is NOS I got from a reliable forum member. It didn't work.

I only got the aftermarket one because it didn't work.

So you think I should buy a 2nd Bosch VR, only a modern one? How much are they? About $200, right?

Cannot see why the new SS VR I just got shouldn't work......

Pretty sure my GEN bulb is original, but will check it tomorrow - know it has to be 2 watt.

Thanks,

GN

You can't use just any light for the alternator light. It has to be a particular bulb to make the circuit work.

If you can connect DF to the positive battery post with the engine running, and get 17+ volts, then the alternator and harness is good. I would change the voltage regulator. Get a Bosch regulator, not some aftermarked reproduction.

[Gatornapper]

Clay -

The strong implication of this statement in the Pelican article, "Too low a wattage bulb will not supply enough field current for "bootstrap" operation to be reliable. The Bosch book that I have states that the lamps must be at least 2 watts for 12 volt systems.", is that a higher wattage bulb, like I used in my test, should be no problem.

The problem is with a lower wattage bulb.

GN

You can't use just any light for the alternator light. It has to be a particular bulb to make the circuit work.

If you can connect DF to the positive battery post with the engine running, and get 17+ volts, then the alternator and harness is good. I would change the voltage regulator. Get a Bosch regulator, not some aftermarked reproduction.

[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.

[Gatornapper]

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...Correct.

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. YES. 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? YES. 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.3 VR's, 2 which are new, this occurred.

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: I agree - just stabbing in the dark for what's going on.....

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. I read zero resistance between each point of D+, DF, and D- between the VR pins and the alternator harness pins.
Read voltage from each point to ground? Will do.

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.

Good idea. Will do.

What is strange to me is that once armature is excited/energized, it won't stay energized - or so it seems. This should not be. As the voltage across the GEN lamp is zero with a working VR and alternator once system is running, the initial exciting of the armature is enough. Correct?

Spoke - thanks for hanging with me on this. Thanks for the patience. Very frustrating for me - fixing electrical problems is my strong suite, and this is the first time ever I haven't found what is wrong and corrected it in my long life. I think there is something here about this system I am not seeing. But in actuality, the circuitry is very simple - as you well know.

[euro911]

At this point I'm suspecting one of the alternator diodes has gone bad.

I'd cut to the chase and try another alternator. Maybe another local member has a (known good) spare that you can try & buy (IMG:style_emoticons/default/confused24.gif)

[Gatornapper]

Mark -

Totally understand - but if one of the diodes were bad, I don't see how the alternator could put out a full 17+ volts on the test jumping D+ and DF, which my alternator did.

Unit also put out full 14.1v on other diode test......

I think something else is going on. Some think only the $200 Bosch VR will fix things.

Don't know anyone with an good alternator. If I have to pull it, pretty sure I can rebuild it myself.

Thanks,

GN

At this point I'm suspecting one of the alternator diodes has gone bad.

I'd cut to the chase and try another alternator. Maybe another local member has a (known good) spare that you can try & buy (IMG:style_emoticons/default/confused24.gif)

[Spoke]

At this point I'm suspecting one of the alternator diodes has gone bad.

I'd cut to the chase and try another alternator. Maybe another local member has a (known good) spare that you can try & buy (IMG:style_emoticons/default/confused24.gif)

An easy way to test for burned diodes is to remove the VR and short DF to D+.

The alternator will produce maximum output.

At this point if all diodes are good, the battery voltage to chassis should equal the D+ voltage to chassis.

[VaccaRabite]

At this point I'm suspecting one of the alternator diodes has gone bad.

I'd cut to the chase and try another alternator. Maybe another local member has a (known good) spare that you can try & buy (IMG:style_emoticons/default/confused24.gif)

An easy way to test for burned diodes is to remove the VR and short DF to D+.

The alternator will produce maximum output.

At this point if all diodes are good, the battery voltage to chassis should equal the D+ voltage to chassis.

(IMG:style_emoticons/default/agree.gif) (IMG:style_emoticons/default/agree.gif) (IMG:style_emoticons/default/agree.gif)

You need to know if the alternator is doing anything.

You will know immediately once DF is shorted to D+. The engine will suddenly have the full load of the alternator dragging on it and RPMs will drop. Using your meter should show 16-18 volts at idle this way. Don't do this longer then needed though, as you will be overcharging your battery.

Zach

[Gatornapper]

Memories guys? Jerry & Zack - Long ago I jumped D+ & DF and did get full 17v at the battery and reported on that numerous times to support my view that the alternator is fine. Even ran the test multiple times.

Also put 12+v to DF as the Pelican article suggests to check all the other diodes, and it too produced a full 14.1 v at the battery, showing all the other alternator diodes are good.

Today verified that the GEN light is indeed 2 watts - and just for the fun of it installed a new 2 watt lamp.

No change.

Thanks,

GN

At this point I'm suspecting one of the alternator diodes has gone bad.

I'd cut to the chase and try another alternator. Maybe another local member has a (known good) spare that you can try & buy (IMG:style_emoticons/default/confused24.gif)

An easy way to test for burned diodes is to remove the VR and short DF to D+.

The alternator will produce maximum output.

At this point if all diodes are good, the battery voltage to chassis should equal the D+ voltage to chassis.

[Spoke]

...I jumped D+ & DF and did get full 17v at the battery...

I would like you to repeat this test and measure:

1) Battery voltage to chassis
2) D+ voltage to chassis
3) GEN light goes out

We're looking to see that VBAT and D+ are exactly the same. This would verify that the diodes in the VBAT path and D+ path are functioning.

If VBAT not equal to D+, then diodes in the alternator may be suspect. The GEN light might be lit as well if VBAT != D+.

If VBAT == D+ AND GEN light goes out, then likely the alternator is ok. This also means that the GEN light provides enough current excite the armature and to bootstrap the alternator into functionality.

If the alternator passes this test, then we suspect the VR AND/OR the wiring to/from the VR. Generating a voltage at DF to excite the alternator is the responsibility of the VR. Thus my request to measure the voltages D+, DF, and D- to chassis directly at the VR connector. If D+ is less than 13-14V, then the VR should raise the voltage at DF to further excite the alternator to produce voltage/current.

No voltage at the DF pin on the alternator connector with D+ less than 14V and D- around zero volts points to the VR and its wiring.

[Spoke]

Here's a way to do a quick test on the VR. I just did this on my 914. The goal is to see if the VR will raise the voltage at DF.

There are 2 parts to this test. This is part 1; Isolation of the VR.

The set up for test 1 is as follows:

1) Remove the connector to the alternator. This will remove the load on DF and isolate the VR. This also removed the ground connection to the VR which will be reconnected in step 4.

2) Remove the power to the FI ECU (if you have FI). If you have carbs, remove the ground jumper from the FI connector on the relay board. This jumper powers the fuel pump. We want the fuel pump off.

3) Remove the 12V connector to the ignition coil. This keeps the points/Pertronix/electronic points from being powered. If you have some other electronic ignition system, remove 12V power from the unit.

4) Ground the D- pin at the alternator connector on the relay board. When you disconnect the alternator plug, the VR loses its ground. I used the jumper wire from the FI ECU connector for the fuel pump to ground D- as shown below.

5) Turn the ignition key to ON.

6) Observe that the GEN light is OFF.

7) At the alternator socket on the relay board, measure D+ to chassis and DF to chassis. On my car, I measured about 10.5V at both D+ and DF.

8) Turn the ignition key to OFF.

Notes:
At step 7, the VR on my 914 sensed only 10.5V and attempted to drive the armature via DF to a high voltage.

The resting voltage of the battery on my car was 12V. This seems low although all exterior marker lights (LEDs) were on as I've rewired the lights to come on when the ignition is ON.

[Spoke]

Part 2 of the VR test is to check the D+ and DF voltages with the alternator connected to the VR.

The set up for test 2 is as follows:

1) If test 1 was just run, all wires are connected as needed. If test 1 was not run, do steps 1 through 4.

2) Remove the ground jumper on the D- pin at the alternator connector on the relay board.

3) Connect the alternator cable to the alternator connector on the relay board. Now the alternator/VR are connected as in the running condition.

4) Turn the ignition key to ON, do not start the car.

5) Observe the GEN light on brightly.

6) At the alternator socket on the relay board, measure D+ to chassis and DF to chassis. On my car, I measured about 2.3V at D+ and 1.5V at DF.

7) The test is done. Reconnect the FI ECU or fuel pump connections. Reconnect the ignition wires to the coil.


Notes:
On my 914, very little voltage was present at D+ and DF since most of the voltage was dropped across the GEN light. Even with only 2.3V at D+, the VR still raised the voltage DF to 1.5V.

Once spinning when starting the car and initial engine running, this little voltage to DF should be enough for the alternator to generate at least a few more volts at D+ which will drive the DF (armature) even higher in voltage thus producing more voltage until the alternator/VR reaches 13-14V and the system is now in regulation.

[Gatornapper]

Ok, will do today.

One additional bit of info: GEN light is OUT when engine is idling.....only comes on with rpm increase, more rpm = brighter GEN light. Bat to chassis when light is OUT is about 12.2 on a fully-charged 12.6 v resting battery.

GN

...I jumped D+ & DF and did get full 17v at the battery...

I would like you to repeat this test and measure:

1) Battery voltage to chassis
2) D+ voltage to chassis
3) GEN light goes out

We're looking to see that VBAT and D+ are exactly the same. This would verify that the diodes in the VBAT path and D+ path are functioning.

If VBAT not equal to D+, then diodes in the alternator may be suspect. The GEN light might be lit as well if VBAT != D+.

If VBAT == D+ AND GEN light goes out, then likely the alternator is ok. This also means that the GEN light provides enough current excite the armature and to bootstrap the alternator into functionality.

If the alternator passes this test, then we suspect the VR AND/OR the wiring to/from the VR. Generating a voltage at DF to excite the alternator is the responsibility of the VR. Thus my request to measure the voltages D+, DF, and D- to chassis directly at the VR connector. If D+ is less than 13-14V, then the VR should raise the voltage at DF to further excite the alternator to produce voltage/current.

No voltage at the DF pin on the alternator connector with D+ less than 14V and D- around zero volts points to the VR and its wiring.