Alternator Giving Very High Volts

[KentABQ]

Sorry to hear you may have to sell, Hamid. After all this effort and expense, you should be enjoying the fruits of your labor. But I feel your pain, because getting older is a major pain in the @&&...and everywhere else!

On the plus side, your bus is running again, which commands a higher price than when a "ran when parked" label is added to the listing.

If you need any support or guidance, you know there are hundreds of fellow Sambanistas here for you. Best of luck to you, brother.
_________________
-Kent-
1976 Riviera, 1.8l FI chrome yellow VAN - "Chloe"

"I must say, how can you be in a bad mood driving this vehicle full of vibrant color.
Cars of today are so bland in comparison. It's like driving a celebration!" ---WildIdea

Bus ownership via emoticons:
---williamM

[timvw7476]

Thanks for checking in Hamid. Sorry about the limitations, I've got
4 vertebrae fused (T4 fracture). There was plenty of pain after surgery
& I actually swapped from a Super Beetle to a Bus for more legroom !
Working on VWs is a form of movement therapy if you can tolerate it.
But too much pain is too much pain & you will judge for yourself.
I remembering needing an automatic transmission for months & months!
Yes, it sucked, I felt like one of those normal people, the ones with ABS
& airbags. Good luck with the bus & your choices.

[smitty1976bus]

I unfortunately have to bring up this thread again

I've been driving my bus since my last post, so little more than a month, and havent had any issues with high volts. The volts get a little lower than I like when the engine gets hot, but Im running the old style VR, so its probably that.

I bought a bunch of new parts, to get the bus ready for long trips, and purchased a new VR. Went to install it, and BAM, high volts again. Same exact issue. The old VR doesnt work either. So what the heck is going on here?!

The battery was giving on good volts, just sitting:

Then when the engine is on:

Yup. Way too much juice. I only leave it running for seconds, not to damage anything. I even went out and bought a new battery, and that did nothing at all to change the results.

I'm all out of ideas. New alternator. New VR. New Battery. New wiring harness. What else is there to this setup?? Why would unplugging the VR screw everything up?

[smitty1976bus]

Ok, did some more testing...

[telford dorr]

Q: was this measurement made with the regulator disconnected? It needs to be, otherwise it becomes an unwanted part of the measurement.

Here's what we're checking:

- the green (Df) and brown (D-) alternator wires are connected via brushes to either end of the rotor winding.

- this winding, and its associated wiring, are supposed to be isolated from everything (specifically, ground).

- you should be able to measure a small resistance (a couple of ohms) between these wires. If not, then either (a) the rotor winding is damaged or open, (b) the brushes are worn out, or (c) the wiring to the alternator is damaged. Any of these conditions will cause the alternator to produce no output.

- you should not be able to measure any conduction (e.g. should have infinite resistance) from either wire to anything (specifically, ground). If you do, it means that either (a) the rotor winding is shorted to the rotor, (b) a brush is damaged and is touching something it shouldn't, (c) there is a problem with the rotor slip rings, and something there is touching ground, or (d) there is a short in the alternator wiring. Any of these conditions could cause the regulator to lose control, and the alternator to run wide open. If you do measure any conduction to something, it should be the same on either wire (green or brown).

Note: none of these measurements should be polarity sensitive (it shouldn't matter which meter probe is where.

Assuming the regulator was disconnected, it sounds to me like there's an intermittent short of some kind in the wiring around the regulator, as moving it corresponds with this alternator runaway condition.

Side note: the battery voltage should decrease slightly as the regulator (and therefore the battery, which is why they are mounted close to each other) warm up, because the full charge voltage of the battery is temperature dependent, and drops as the battery temperature rises. The regulator has a temperature-sensitive component that is supposed to compensate for this effect.
_________________
'71 panel, now with FI
'Experience' is the ability to recognize a mistake when you're making it again - Franklin P. Jones
In theory, theory works in practice; in practice, it doesn't - William T. Harbaugh
When you're dead, you don't know you're dead. The pain is only felt by others.
Same thing happens when you're stupid. - Philippe Geluck
More VW electrical at http://telforddorr.com/ (available 9am to 9pm PST)

[telford dorr]

[delete]
_________________
'71 panel, now with FI
'Experience' is the ability to recognize a mistake when you're making it again - Franklin P. Jones
In theory, theory works in practice; in practice, it doesn't - William T. Harbaugh
When you're dead, you don't know you're dead. The pain is only felt by others.
Same thing happens when you're stupid. - Philippe Geluck
More VW electrical at http://telforddorr.com/ (available 9am to 9pm PST)

[smitty1976bus]

Thank you for the response telford dorr, you really know this stuff, much appreciated.

[telford dorr]

[SGKent]

this has probably been mentioned before in this thread but it needs to be said again. The washer and post that hold the main wire are known to short out / arc over on the alternator cover. The mark where they short is quite faint but can be seen on the cover. If this happens it will cause a high load on things. be sure that isn't happening, and that there is a gasket between the cover and alternator.

https://www.thesamba.com/vw/forum/viewtopic.php?t=655415&highlight=bosch+alternator+washer

[smitty1976bus]

[telford dorr]

I see what appears to be a strap grounding a brush and the D- terminal and, contrary to my understanding, it looks to be factory stock. So stand by for a day. I'm going to pull a working alternator, disassemble it, document it, and do a general sanity check.

While you're waiting, take a small piece of scotchbrite pad and buff up those slip rings inside the alternator by holding the pad against them and spinning the pulley. When done, measure the resistance between the two rings, and report back the value. Also measure the resistance between each ring and the alternator case (it should be infinite).

Now clean up the brush holder in a little solvent. Check how long the individual brushes are. They should be long enough to easily reach and touch those two slip rings, with some length to spare. Carefully clean the area on the alternator case where those two brush holder lugs touch. Reinstall the brush holder into the alternator. Measure the resistance between the D- and Df terminals, and report back the reading. I'll compare the numbers to my alternator.

If your meter has a 'diode' resistance range, measure from the D+ terminal to ground. Repeat the measurement with the probes reversed. One probe polarity should read infinite. The other should give you a resistance reading through the 'diode trio' inside the alternator. Report the reading.

Thanks.
_________________
'71 panel, now with FI
'Experience' is the ability to recognize a mistake when you're making it again - Franklin P. Jones
In theory, theory works in practice; in practice, it doesn't - William T. Harbaugh
When you're dead, you don't know you're dead. The pain is only felt by others.
Same thing happens when you're stupid. - Philippe Geluck
More VW electrical at http://telforddorr.com/ (available 9am to 9pm PST)

[smitty1976bus]

Much appreciated man.

Ok, so I have my old alternator, and the freshly rebuilt one from BusDepot. i'll compare the two when testing. When removing the cover on the rebuilt unit, it looks like they just cleaned up an old unit and put new brushes in, the wires were still old (like on my old one) and there was not gasket sealing it up. not entirely impressed with the rebuild:

Here is the plugs from the old and rebuilt unit compared next to one another:

The brushes have definitely been worn down on the old unit:

[telford dorr]

OK, mea culpa time. I have apparently mis-remembered type 4 style alternators. Probably old age catching up (getting old sucks)... Having finished bench inspecting an AL75X (55 amp) alternator / regulator / harness, I indeed find the D- alternator lug is grounded, not floating. I've no idea how this brain fart happened, or what I confused this with. Too many alternators, I guess...

In any event, everything above regarding the D- wire is COMPLETELY WRONG - ignore it. My bad - sorry.

Here's the corrected version:

- measuring from D- to alternator case should read zero ohms.

- measuring across the rotor slip rings (on my unit) reads 4.1 ohms. I would expect a 70 amp unit should be similar, within a few ohms. Next time I see one, I'll measure it.

- measuring between D- and Df at the regulator reads 4.3 ohms. Note: to get this, all terminals on the alternator and harness were buffed with a Dremel tool wire wheel until shiny, then given a thin coat of dielectric grease before assembly.

- the only way to get alternator runaway without the regulator connected is to have a short between D+ and Df. If unplugging the regulator stops all alternator output, but plugging the regulator in causes high volts, the problem is most likely the regulator, not the alternator or harness. The test is to measure the voltage at both the regulator D+ terminal and at the battery '+' terminal. If they're both the same (they should be very close), then the regulator is bupkis. If the D+ voltage is much lower, like a normal 13.8 to 14.4 volts, then there's either an issue on the regulator blue wire circuits that's loading down the D+ voltage, or the alternator diode trio is bad. Note: the regulator regulates using the D+ terminal voltage, NOT the battery voltage. It actually has no idea what the battery voltage is. It just assumes D+ and B+ are the same voltage. The test is to disconnect the regulator blue wire from the rest of the bus, and connect a test light between the regulator blue wire and the battery '+' terminal. If this causes the battery voltage to return to normal, then the alternator and regulator are fine, and the real problem is in the bus blue wire wiring.

- even though we (now) know that D- is grounded, there is no internal connection between the regulator D- terminal and the regulator case (on my regulator). But there is a connection between the regulator case and the internal regulator circuitry. This means the regulator case must be well grounded to function properly. Also, as the regulator is typically mounted on the gas tank cover plate, we assume that the cover plate is well grounded. To verify, measure the voltage from the regulator case to the battery '-' terminal. There shouldn't be any.

That's a far as I got today. Tomorrow, I need to weld up a bracket (a couple hour project, assuming I have enough small square tubing and strap in stock) to hold a type 4 alternator to my generator / alternator test stand (shown below, with an AL82N mounted). Once that's done, I'll fire this type 4 alternator up and get some running measurements. Stand by for more - pics, numbers, etc..

These numbers all look to be in the ballpark (the D- to Df resistance on the old alternator is probably the worn brushes or cruddy terminals on the brush holder). My guess is the alternators are OK, and the regulator is suspect. Make sure the terminals are all nice and clean, and that the regulator case is well grounded (buff up the mounting ears).

Note: in diode test mode, the meter applies a current to, and measures the voltage drop across the diode (typically 0.6 to 0.8 volts). In this case we're effectively measuring two diodes in series (1.2 to 1.6 volts). Thus, your 1317 reading is actually 1.317 volts, not really ohms. This only applies to the diode test range on the ohms scale.
_________________
'71 panel, now with FI
'Experience' is the ability to recognize a mistake when you're making it again - Franklin P. Jones
In theory, theory works in practice; in practice, it doesn't - William T. Harbaugh
When you're dead, you don't know you're dead. The pain is only felt by others.
Same thing happens when you're stupid. - Philippe Geluck
More VW electrical at http://telforddorr.com/ (available 9am to 9pm PST)

[smitty1976bus]

[dualbay]

[telford dorr]

[sestino]

The problem of an alternator giving high volts reminds me of the problem I had 2 years ago when I replaced my VR for my 70 amp alternator with a Beru VR -- it surged to 16 volts and I replaced it with an Ebay product that works fine:

[telford dorr]

OK, I cobbed up an alternator holder for my test stand (yeah, it needs finish work and paint, but I ran out of time today):

It also mounts the regulator (hidden in the rear; bolted and grounded to the test stand). The alternator is driven by a four pole 1 hp induction motor, and spun at around 1890 rev/min (roughly a low engine idle speed, after engine belt gear ratio factored in). The alternator assembly is connected to a car battery. A test light is used as a stand-in for the ALT dash indicator.

Firing the unit up yielded the following voltage readings (no load except the battery, which was allowed to charge for a while):

B+ (at harness lug) = 14.11 vdc
D+ (at harness blue wire) = 14.14 vdc
Df (at regulator connector) = 4.49 vdc
D- (at harness connector) = -0.06 vdc (note: reading is negative because D- references an internal alternator ground connection, whereas meter ground is the test fixture base plate, and thus measures the voltage drop between the two)

Ground was the steel plate of the test fixture.

Loaded readings (load was a headlight bulb with both high and low beam activated):

B+ = 13.84 vdc
D+ = 14.01 vdc
Df = 6.17 vdc (this voltage will rise with loading because the regulator is requesting more alternator output)
D- = -0.19 (more voltage drop because the alternator is outputting more current)

Note: loaded operation was minimized due to a lack of alternator cooling air with this setup. Don't want to overtemp a diode...

So, we can see the following trends:

1) the regulator regulates based on the D+ and D- voltage differential, which will not vary very much. Note the D+ - D- voltage (14.14 + 0.06 = 14.20, unloaded, and 14.01 + 0.19 = 14.20, loaded) is the same in both cases. The B+ voltage will vary a bit as alternator loading is increased. This shows the importance of a solid alternator mount to the engine and a solid trannie ground strap, to minimize voltage drop between the alternator and body ground, resulting in more voltage to the battery. The voltage at the battery will vary with load as a function of how good all of the connections are between the battery and the alternator are. Alternator mount, trannie ground strap, and battery cable connections need to be as good as possible for maximum battery voltage (and thus charge) to be realized.

2) the Df voltage will vary quite a bit as alternator load is changed. More load will cause the regulator to increase this voltage significantly.

Diagnostic considerations:

1) if the battery voltage is very high, check the voltage between D+ and D-. If it is also high, check the voltage between Df and ground. If it is also high, then either (a) the regulator has failed, and is causing the alternator to run wide open, or (b) there is a short between Df and battery +, bypassing the regulator and again causing the alternator to run wide open. If disconnecting the regulator kills the alternator output, the regulator is the problem. If it doesn't, then it's likely a harness short or an internal alternator short of some kind. If Df is low, then the alternator small diodes may have partially failed, causing the regulator to overdrive the alternator Df terminal. Connect a large test light (like a brake or turn signal bulb) between D+ and battery +. If this returns things to normal, then the small alternator diodes are toast.

1) if there is no alternator output, check the Df voltage. If it is high (12 volts), then either the alternator brushes are worn out, or the big alternator diodes have failed. If the Df voltage is low, suspect a regulator problem. There should be some voltage at D+. If nothing, then if the dash indicator is lit, the small alternator diodes may have failed. If the dash indicator is dark, check the bulb and any other connections to the blue regulator wire. Disconnect and ground the body side blue wire. This should make the indicator light. When in doubt, disconnect the blue wire, and wire a test light between battery + and the blue wire stub at the regulator. If this restores thing back to normal, inspect the body side blue wire connections for problems.
_________________
'71 panel, now with FI
'Experience' is the ability to recognize a mistake when you're making it again - Franklin P. Jones
In theory, theory works in practice; in practice, it doesn't - William T. Harbaugh
When you're dead, you don't know you're dead. The pain is only felt by others.
Same thing happens when you're stupid. - Philippe Geluck
More VW electrical at http://telforddorr.com/ (available 9am to 9pm PST)

[telford dorr]

[Last addition to this thread]
Finished test fixture, showing regulator mounted to baseplate.:

---
Definitive Regulator Bench Test Method

If you have access to a variable voltage DC power supply, here is an easy but definitive bench test method for a T4 style alternator regulator. You need:
- a variable voltage DC power supply that can be varied between 12 and 15 volts, minimum range.
- a test light.
- a DVM.

Connect as follows:
- power supply negative to both regulator case ("ground") and D- (brown wire).
- power supply positive to regulator D+ (red wire).
- test light from regulator Df (green wire) to ground.

Procedure:
- set the power supply to 12 volts. The test light should illuminate. If it doesn't, the regulator is bad.
- slowly increase the power supply voltage. The test light should get brighter. Keep increasing. Somewhere around 14.1 volts, the test light should suddenly go out. Decreasing the voltage slightly will make it come back on. The transition is fairly sharp. This is the regulation voltage. It should be somewhere between 13.8 volts and 14.4 volts, depending on temperature (colder = higher volts). If the light doesn't toggle on/off somewhere within this range, the regulator is bad.

That's it.
_________________
'71 panel, now with FI
'Experience' is the ability to recognize a mistake when you're making it again - Franklin P. Jones
In theory, theory works in practice; in practice, it doesn't - William T. Harbaugh
When you're dead, you don't know you're dead. The pain is only felt by others.
Same thing happens when you're stupid. - Philippe Geluck
More VW electrical at http://telforddorr.com/ (available 9am to 9pm PST)

[smitty1976bus]

Can't thank you enough telford dorr . I had no idea how the chargning system worked on my bus, but I think I grasp it now... well 75% understand it. ha. I received my replacement alternator from BusDepot the other week, and did the resistance tests, just as I did with the last one, and received similar (just about identical) results. Wish I had the tools to bench test it before installing it; but couldn't (thought about using my compressors electric motor, and rigging something up, but decided against it)

Ended up installing the alternator and wiring it up, making sure that all the wires mirrored the same resistance which it plugged into, all looked good. Also ran a ground strap from the VR to a known ground (believe this could be the original problem). Now came the time to start the engine and watch those volts! Always a nervous moment... And of course.. she wouldnt start. ha. No idea why, so went through all the normal trouble shooting, and eventually came to the culprit.. the fuel injectors series resistors pack. This is why it took a couple weeks to reply to this thread, I had to locate a resistor pack. I wonder if the high volts from the previous alternator fried it?? Maybe.

Anyways, the engine starts now, and the volts are amazing! Right at 14.4. Such a good feeling. Now, I should mention that I've only tested this on the old style VR, I haven't tried those new solid state units. Maybe I'll try it sometime.. maybe.

It's been a long, crazy, hair ripping out, journey to solve this problem. Thank you to all who helped! Hopefully I won't have to come back to this thread with another high voltage issue. Hopefully it helps someone else down the road. Everything you need to know about a 70 amp alternator, VR wiring harness, and remember to ground those VR units!

Thanks
Smitty