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> Alternator question., Not Charging.
Olympic 914
post Mar 25 2018, 05:05 PM
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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?
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GregAmy
post May 13 2018, 01:22 PM
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That post #15 is a gem...

Camping onto this one for a slightly different problem: GEN light comes on strong with key on, engine not running, But then the GEN light glows very soft at idle, and then comes on stronger as RPMs build. Battery is getting ~13.5 volts when running.

QUOTE
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.

Check. I get around 15.5V at idle and up to 17+ as I rev it up.

QUOTE
To check the D+ portion of the system, it is necessary to find out if the D+ output can produce enough current to drive the alternator to full output. To do this, short the D+ and DF terminals on the relay board. This will provide the maximum field current to the alternator that the alternator ITSELF can supply

Check. Same as above, 15+ V at idle and 17+ as I rev it up.

Problem is, I can't check to see if it extiguishes the GEN light, because my GEN light is not on with the voltage regulator removed. It'll only come on with the regulator installed. This makes sense, because looking at the wiring diagram the ground side of the GEN light is through the voltage regulator; it's blocked by diodes at the alternator from grounding.

Does everyone else's GEN light come on with key on and engine off when the VR is removed?

I did some further checks. Pulled the combo gauge out and measured voltage at the GEN light housing. With the engine off I'm getting 0V across the terminals, but with the engine running I'm getting ~2V at idle with the blue (D+) wire hotter than the red (system) voltage wire, rising to nearly 4V at revs. Measured to ground, I'm getting system (~13.5V) voltage from the S9 fuse and ~15.5V at idle and ~17.5V (max alternator output) at the blue D+.

That would certainly explain the glowing bulb.

So here's the key question: what is supposed to be at D+? I'm guessing the same as system. B+ is being regulated, so the rest of the car is getting the proper voltage, it's just the D+ wire that's too hot. Unfortunately, I don't know enough about these systems to understand why that could happen.

Since the rest of the car is not overcharging it seems safe to drive, and it'll still glow bright if I fail the alternator, but I'd prefer to not ignore it.

I REALLY don't want to replace the alternator in this thing...Thoughts appreciated.

Greg

Edit: an added data point. I swapped out the Hella solid state VR for a resgular Bosch VR of unknown provenance. Now I'm getting 13.5 on the D+ side and 12.2 on the B+ side. I might just buy a new VR from a local FLAPS and see if that resolves it.
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Spoke
post May 13 2018, 02:20 PM
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QUOTE(GregAmy @ May 13 2018, 03:22 PM) *

Does everyone else's GEN light come on with key on and engine off when the VR is removed?

Yes, the light is on with key on and engine not running and off with VR removed.

QUOTE

Measured to ground, I'm getting system (~13.5V) voltage from the S9 fuse and ~15.5V at idle and ~17.5V (max alternator output) at the blue D+.

That would certainly explain the glowing bulb.

I'm not sure I follow your measurements. What are the 2 measurements at S9 and D+ both to ground at the same condition with the VR installed? At idle and 2k RPM. The difference between the voltage at S9 and D+ is the voltage across the GEN light.

These 2 voltage come from the 2 steering diode pins on the alternator which derive voltage from the same stator windings. They should always be the same during operation. This could point to alternator diode issue although I wouldn't replace the alternator unless sure it's not the VR. It would be convenient to swap the VR for a known good one before buying a new VR.

QUOTE

So here's the key question: what is supposed to be at D+?


D+ doesn't matter in this case. D+ is the voltage across the armature to provide field current for the armature coil. It will vary with load. The VR controls this.

QUOTE

Since the rest of the car is not overcharging it seems safe to drive, and it'll still glow bright if I fail the alternator, but I'd prefer to not ignore it.


Agreed it should be ok as long as the battery voltage stays above 13V and below 15V.
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GregAmy
post May 13 2018, 03:45 PM
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QUOTE(Spoke @ May 13 2018, 04:20 PM) *
Yes, the light is on with key on and engine not running and off with VR removed.

How? Look at the wiring diagram: if you remove the voltage regulator then to what circuit will the GEN lamp ground? The diodes in the alternator should stop it from being grounded there, leaving only the circuits in the voltage regulator...so, to the wiring diagram, the GEN light should not be on with the VR removed and the key on.

Have you observed it that way yourself? If not, give it a try.

QUOTE
I'm not sure I follow your measurements. What are the 2 measurements at S9 and D+ both to ground at the same condition with the VR installed?


Exactly as I wrote above: "Measured to ground, I'm getting system (~13.5V) voltage from the S9 fuse and ~15.5V at idle and ~17.5V (max alternator output) at the blue D+."

Direct to battery using the same ground is within 0.2V of S9, as measured on the S9 side of the GEN light housing.
QUOTE
These 2 voltage come from the 2 steering diode pins on the alternator which derive voltage from the same stator windings. They should always be the same during operation.

"Should".

Ain't.
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Spoke
post May 13 2018, 05:30 PM
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QUOTE(GregAmy @ May 13 2018, 05:45 PM) *

QUOTE(Spoke @ May 13 2018, 04:20 PM) *
Yes, the light is on with key on and engine not running and off with VR removed.

How? Look at the wiring diagram: if you remove the voltage regulator then to what circuit will the GEN lamp ground? The diodes in the alternator should stop it from being grounded there, leaving only the circuits in the voltage regulator...so, to the wiring diagram, the GEN light should not be on with the VR removed and the key on.

Have you observed it that way yourself? If not, give it a try.

QUOTE
I'm not sure I follow your measurements. What are the 2 measurements at S9 and D+ both to ground at the same condition with the VR installed?


Exactly as I wrote above: "Measured to ground, I'm getting system (~13.5V) voltage from the S9 fuse and ~15.5V at idle and ~17.5V (max alternator output) at the blue D+."

Direct to battery using the same ground is within 0.2V of S9, as measured on the S9 side of the GEN light housing.
QUOTE
These 2 voltage come from the 2 steering diode pins on the alternator which derive voltage from the same stator windings. They should always be the same during operation.

"Should".

Ain't.


I re-read my post and I had a few things wrong.

= With VR removed and engine not running, S9 is battery voltage (12.6V). The load looking into the D+ wire is infinite since the VR is the only load. and with the VR removed, electrically you only see the cathodes of the 3 alternator diodes. The GEN light doesn't light since current cannot flow into the cathodes of the 3 diodes.

= I said the voltage at D+ doesn't matter. I had confused D+ with DF. D+ should be exactly the same as the battery voltage. DF is variable with load and is controlled by the VR.

= About the measurements, here's what I think you've measured with the VR INSTALLED:

At idle:
V(S9) V(D+)
13.5V 15.5V

At elevated RPM
V(S9) V(D+)
13.5V 17.5V

Or are these numbers with VR REMOVED and D+ directly connected to DF?

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GregAmy
post May 14 2018, 03:55 PM
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QUOTE(Spoke @ May 13 2018, 07:30 PM) *

= About the measurements, here's what I think you've measured with the VR INSTALLED:

Prior to start up
12.15V at the battery.

Voltage between from combo gauge housing (my ground inside) to battery 12.15

Key on, removed bulb:
11.83V between combo housing and red/white wire
0V between combo and blue wire

So my S9 circuit has a dirty connection somewhere, I'm losing 1/2V to the combo gauge.

Bulb back in, start car:
13.35V battery to combo gauge housing

13.32V between combo housing and red/white wire @ idle
~15.5v between combo housing and blue wire @ idle
Bulb glowing slightly

13.51V between combo housing and red/white wire @ revved
17.34V observed between combo housing and blue wire @ revved
Bulb glowing brighter, but not as bright as key on engine off.

Reminder: when I tested Battery to D+ and DF to D+ I got max alternator voltage both times.

So why is D+ showing max alternator output voltage when it's supposed to be the same as B+?

I'm'a gonna hit a FLAPS for a new voltage regulator, not really hopeful but fingers crossed.
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Posts in this topic
Olympic 914   Alternator question.   Mar 25 2018, 05:05 PM
Spoke   Took the car out for a drive today, planning on g...   Mar 26 2018, 07:21 AM
Olympic 914   Yes, disconnect only the VR. Jump the D+ and DF...   Mar 26 2018, 08:37 AM
falcor75   Ground cable between gearbox and chassi?   Mar 26 2018, 08:47 AM
Olympic 914   Ground cable between gearbox and chassi? New, C...   Mar 26 2018, 08:55 AM
Mikey914   Well if all works well great. I'd try driving ...   Mar 26 2018, 09:40 AM
Olympic 914   Well if all works well great. I'd try driving...   Mar 26 2018, 09:50 AM
Olympic 914   So this alternator problem continues to vex me. ...   Apr 18 2018, 07:20 PM
malcolm2   Next step will be to pull the alternator and pro...   Apr 19 2018, 08:04 AM
McMark   Dying relay board?   Apr 19 2018, 05:30 AM
Olympic 914   Dying relay board? I did hook up another relay ...   Apr 19 2018, 06:20 AM
malcolm2   I have had some ALT probs too. Spoke must keep th...   Apr 19 2018, 07:08 AM
McMark   I think malcolm2 is right -- and I don't think...   Apr 19 2018, 07:34 AM
Tdskip   I think malcolm2 is right -- and I don't thin...   Mar 28 2019, 06:13 AM
malcolm2   I am bored today. Hey Spoke, how is this???   Apr 19 2018, 09:13 AM
Olympic 914   There is also this. I performed the tests belo...   Apr 19 2018, 11:55 AM
McMark   Damn!!! That’s a fantastic post. :dr...   Apr 19 2018, 04:09 PM
bulitt   Yes, you must excite the Alternator to wake it up....   Apr 19 2018, 04:58 PM
Mikey914   Yes, you must excite the Alternator to wake it up...   Apr 20 2018, 10:20 AM
Edward Blume   I had my stock Bosch alternator professionally reb...   Apr 19 2018, 05:58 PM
jcd914   I don't recall the years but there was a TSB f...   Apr 20 2018, 10:36 AM
Olympic 914   On Thursday took the alternator to the local FLAPS...   Apr 22 2018, 11:52 AM
Spoke   :beer2:   Apr 22 2018, 12:07 PM
GregAmy   That post #15 is a gem... Camping onto this one f...   May 13 2018, 01:22 PM
Spoke   Does everyone else's GEN light come on with k...   May 13 2018, 02:20 PM
GregAmy   Yes, the light is on with key on and engine not ru...   May 13 2018, 03:45 PM
Spoke   Yes, the light is on with key on and engine not r...   May 13 2018, 05:30 PM
GregAmy   = About the measurements, here's what I think...   May 14 2018, 05:05 AM
GregAmy   = About the measurements, here's what I think...   May 14 2018, 03:55 PM
GregAmy   Camping onto this one for a slightly different pr...   Mar 25 2019, 07:58 PM
worn   Camping onto this one for a slightly different p...   Mar 25 2019, 08:13 PM
GregAmy   Maximum alternator output is triggered when you b...   Mar 26 2019, 05:06 AM
DRPHIL914   Camping onto this one for a slightly different p...   Mar 27 2019, 10:33 AM
VaccaRabite   Greg, Glad you solved it. My issue was the lacke...   Mar 27 2019, 07:39 PM
euro911   I have several 'unknown condition' units I...   May 14 2018, 02:27 AM
GregAmy   Aaaaand a new voltage regulator... ...didn't ...   May 14 2018, 04:32 PM
Spoke   Bummer. I didn't think the VR was at fault but...   May 15 2018, 07:04 PM
GregAmy   Yep. All grounds and battery cables replaced by me...   May 16 2018, 06:42 AM
dangrouche   Yep. All grounds and battery cables replaced by m...   May 17 2018, 11:27 AM
GregAmy   the pigtail at the alternator end needs the altern...   May 18 2018, 08:07 AM
dangrouche   https://www.aspwholesale.com/index.php here is a ...   May 18 2018, 11:24 AM
Gatornapper   Ok, friends - this thread has been very helpful, b...   Aug 31 2019, 07:07 PM
Spoke   Try these measurements with engine running; lights...   Aug 31 2019, 08:14 PM
Gatornapper   Only work on car had nothing to do with electrical...   Sep 1 2019, 07:20 AM
Spoke   Should I read these voltages at the VR pins as we...   Sep 1 2019, 07:48 AM
Gatornapper   I have quite a bit of experience with circuit boar...   Sep 1 2019, 11:36 AM
Gatornapper   Spoke - Ran tests tonight after 1 hour drive, so ...   Sep 3 2019, 06:26 PM
Spoke   Spoke - Ran tests tonight after 1 hour drive, so...   Sep 3 2019, 07:34 PM
Gatornapper   Spoke - yes, GEN light is OFF until I turn on head...   Sep 3 2019, 08:08 PM
914Sixer   Do you have a spare relay board to swap out?   Sep 1 2019, 07:41 AM
904svo   Just a WAG, measure the voltage between the altern...   Sep 3 2019, 07:28 PM
Gatornapper   Thanks for the idea - I'll do that. But previ...   Sep 3 2019, 07:37 PM
Gatornapper   Re: VR not working. Both VR's I have get ver...   Sep 4 2019, 06:21 AM
Olympic 914   Re: VR not working. Both VR's I have get ve...   Sep 4 2019, 06:45 AM
Gatornapper   Thanks - would like to get one.... Checked BERU...   Sep 4 2019, 09:42 AM
Spoke   Re: VR not working. Both VR's I have get ve...   Sep 4 2019, 07:06 PM
euro911   Typically can't purchase products from compani...   Sep 4 2019, 11:43 AM
Gatornapper   Thanks Mark. Typically can't purchase produc...   Sep 4 2019, 05:21 PM
Gatornapper   Ok, test results: Relay board not the problem.......   Sep 4 2019, 05:28 PM
Spoke   Ok, test results: Relay board not the problem......   Sep 4 2019, 07:24 PM
VaccaRabite   Keep in mind that without the alternator working,...   Sep 5 2019, 07:58 AM
Gatornapper   Zach - First running one to the shroud. Then ch...   Sep 5 2019, 11:03 AM
jcd914   Maybe I missed in the thread but did you check vol...   Sep 4 2019, 05:53 PM
Gatornapper   Jim - will check tomorrow, but checked all other p...   Sep 4 2019, 08:09 PM
Gatornapper   Spoke - Will run all suggested tests tomorrow - ...   Sep 4 2019, 08:23 PM
Spoke   So when I check D- to chassis that's with the...   Sep 5 2019, 04:15 AM
Gatornapper   Dumb question: if the VR is in place, where do I ...   Sep 5 2019, 10:59 AM
Spoke   Dumb question: if the VR is in place, where do I...   Sep 5 2019, 03:58 PM
Spoke   This diagram shows which signals are which. In th...   Sep 5 2019, 04:02 PM
Gatornapper   I should have told you all I don't have regula...   Sep 5 2019, 04:54 PM
Spoke   It makes me wonder if the VR is not starting becau...   Sep 5 2019, 05:41 PM
Gatornapper   Ok, I can do that, but then I need someone else at...   Sep 5 2019, 06:12 PM
Gatornapper   I have another idea: I'll bring a 1 amp fused...   Sep 5 2019, 06:18 PM
Spoke   I have another idea: I'll bring a 1 amp fuse...   Sep 5 2019, 06:41 PM
Gatornapper   Spoke - Ok, let's assume that jumping 12+ to ...   Sep 5 2019, 07:05 PM
Spoke   Spoke - Ok, let's assume that jumping 12+ to...   Sep 5 2019, 07:29 PM
Spoke   I have another idea: I'll bring a 1 amp fuse...   Sep 6 2019, 04:47 PM
Gatornapper   I have another idea: I'll bring a 1 amp fus...   Sep 7 2019, 05:46 AM
Gatornapper   Spoke - D- to engine or chassis with engine runni...   Sep 5 2019, 06:05 PM
914Sixer   Adding information from owners manual. Please rea...   Sep 6 2019, 02:54 PM
Gatornapper   Mark - yes, I know this - so I have 3 bad VR's...   Sep 6 2019, 03:34 PM
914Sixer   I would say the Bosch ones are ok. Is the alterna...   Sep 6 2019, 03:54 PM
Gatornapper   I would say yes. But remember, it puts out full v...   Sep 7 2019, 05:32 AM
Gatornapper   Post I just made on Pelican's forum: Greg - ...   Sep 7 2019, 07:15 PM
ClayPerrine   You can't use just any light for the alternato...   Sep 7 2019, 07:20 PM
Gatornapper   Clay - The 2nd VR I tried is NOS I got from a rel...   Sep 7 2019, 07:53 PM
Gatornapper   Clay - The [b]strong implication of this statemen...   Sep 8 2019, 05:54 AM
Spoke   Did you do the test with the 1156 bulb across the ...   Sep 8 2019, 09:41 AM
Gatornapper   Yes. Nothing happened. Did not energize the arma...   Sep 8 2019, 11:24 AM
Spoke   Yes. Nothing happened. Did not energize the arm...   Sep 8 2019, 04:45 PM
Gatornapper   [quote name='Gatornapper' post='2745248' date='Se...   Sep 8 2019, 06:17 PM
euro911   At this point I'm suspecting one of the altern...   Sep 8 2019, 07:25 PM
Gatornapper   Mark - Totally understand - but if one of the di...   Sep 8 2019, 07:33 PM
Spoke   At this point I'm suspecting one of the alter...   Sep 8 2019, 08:58 PM
VaccaRabite   At this point I'm suspecting one of the alte...   Sep 9 2019, 11:06 AM
Gatornapper   Memories guys? Jerry & Zack - Long ago I jump...   Sep 9 2019, 07:26 PM
Spoke   ...I jumped D+ & DF and did get full 17v at t...   Sep 9 2019, 10:50 PM
Gatornapper   Ok, will do today. One additional bit of info: G...   Sep 10 2019, 07:21 AM
Spoke   Here's a way to do a quick test on the VR. I j...   Sep 9 2019, 11:52 PM
Spoke   Part 2 of the VR test is to check the D+ and DF vo...   Sep 10 2019, 12:04 AM
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