Over Voltage

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drober23
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Over Voltage

Post by drober23 » Wed Mar 27, 2013 7:44 am

I was having trouble with my Propex heater cutting out. It gave the error code of Low Voltage. I checked several times, and never saw it go below the 10 v needed, not even while cranking the engine.

Later, I tested it again with the bus running and noticed that once I put my foot to the gas, the voltage raises over 16V! The unit cuts out at 15V, and the error code is the same for high/low voltage. That mystery is solved, but another is opened.

When I tested the voltage at my battery, I was getting 12 v. I guess I need to test it at the battery with the engine running fast to see what I get. Hmmm... Also, what am I frying if I am sending 16.5 volts through the wires?

[Edit]... Meanwhile, I am looking for answers here and elsewhere. Just found: viewtopic.php?f=48&t=9416
DJ

'75 Westfalia, '79 Deluxe
(plus more busses than sense)

In a time of chimpanzees I was a monkey

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Re: Over Voltage

Post by Amskeptic » Wed Mar 27, 2013 9:27 am

drober23 wrote:I was having trouble with my Propex heater cutting out. It gave the error code of Low Voltage. I checked several times, and never saw it go below the 10 v needed, not even while cranking the engine.

Later, I tested it again with the bus running and noticed that once I put my foot to the gas, the voltage raises over 16V! The unit cuts out at 15V, and the error code is the same for high/low voltage. That mystery is solved, but another is opened.

When I tested the voltage at my battery, I was getting 12 v. I guess I need to test it at the battery with the engine running fast to see what I get. Hmmm... Also, what am I frying if I am sending 16.5 volts through the wires?

[Edit]... Meanwhile, I am looking for answers here and elsewhere. Just found: viewtopic.php?f=48&t=9416
Be careful here. You do not want a run-away situation. Do you have the black cooling duct on the end of your alternator? The harness goes through a grommet and plugs into the alternator with a plug that looks similar to the regulator plug. Check this harness for any chafing or shorts with a multimeter.

It would appear that your regulator/alternator are not reading each other correctly.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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dingo
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Re: Over Voltage

Post by dingo » Wed Mar 27, 2013 9:47 am

alternator can produce too much voltage and overcharge the battery.
Symptoms here would include low battery electrolyte, damaged battery plates from overheating and/or burned out bulbs.
The cause is usually a defective voltage regulator or poor regulator ground connection.
'71 Kombi, 1600 dp

';78 Tranzporter 2L

" Fill what's empty, empty what's full, and scratch where it itches."

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drober23
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Re: Over Voltage

Post by drober23 » Wed Mar 27, 2013 9:48 am

Thanks Colin,
The alternator has a cooling boot. I see the cable going to the alternator. The ends are completely hidden inside the beautiful tin, so I can't get at them at the moment. I agree with your statement that the battery and alternator seem to not be talking to each other at the moment. I will try to intercede and thaw their currently chilly relationship!

Lunch time test! wuwu!

Battery voltage at idle: 12.5 v
Battery voltage at fast (3000 rpm?): 15.9 v

Also: generator light does not light when ignition is ON with engine not running.
Hmmmm.... I thought the alternator was not supposed to work at all in this condition.

DJ
DJ

'75 Westfalia, '79 Deluxe
(plus more busses than sense)

In a time of chimpanzees I was a monkey

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drober23
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Re: Over Voltage

Post by drober23 » Wed Mar 27, 2013 9:50 am

Oh, Dingo,

I read your whole thread, and it doesn't sound like you ever figured out what the problem was. When you mention Voltage Regulator, do you mean one inside the alternator, right? Or do you mean the one inside the firewall.

Thanks!
DJ

'75 Westfalia, '79 Deluxe
(plus more busses than sense)

In a time of chimpanzees I was a monkey

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Re: Over Voltage

Post by Amskeptic » Wed Mar 27, 2013 10:03 am

drober23 wrote: Also: generator light does not light when ignition is ON with engine not running.
Hmmmm.... I thought the alternator was not supposed to work at all in this condition.

DJ
DJ, this is important information coming in late in the game.

Does the bulb work?
If the bulb works, then no light with ignition ON is trouble! That means you are getting 12 volts up the blue alternator wire when it is not running. That is:
A) toasted diode city
B) some kind of short between B+ and D+

Have you been following the Rsorak71Westy superbeetle not charging thread? Read it for a discussion on this idiot light set-up. You get 12 volts to the shell of the idiot light bulb from the ignition switch to the base plate of the cluster. The bulb lights with engine off because the alternator grounds the blue wire circuit. When the *running* alternator puts out, it is supposed to match the ignition switch-provided 12 volts, and the light goes out.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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drober23
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Re: Over Voltage

Post by drober23 » Wed Mar 27, 2013 10:39 am

Will do! I had the dash apart when I replaced the fuel gauge. I bet I borked something up then. Luckily, I've only driven the bus 500 miles since then... :silent:

I'll read the thread on my next break and get after this week (before I get shipped out of the country again).

DJ
DJ

'75 Westfalia, '79 Deluxe
(plus more busses than sense)

In a time of chimpanzees I was a monkey

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drober23
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Re: Over Voltage

Post by drober23 » Wed Mar 27, 2013 2:25 pm

Pulled the blue wire out of the cluster.
Blue wire: Ignition off: 0v
Ignition on: 12v
Engine Running: 12v (idle) - 16v (faster)

Base Plate of Cluster (hole where blue wire came from)
Ignition off: 0v
Ignition on: 12v
Engine Running: 12v (Idle) - 16v (faster)
DJ

'75 Westfalia, '79 Deluxe
(plus more busses than sense)

In a time of chimpanzees I was a monkey

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Amskeptic
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Re: Over Voltage

Post by Amskeptic » Wed Mar 27, 2013 5:13 pm

[quote="drober23"]Pulled the blue wire out of the cluster.
Blue wire: Ignition off: 0v
Ignition on: 12v


Problem. Make sure it is the correct blue wire attached to the alternator idiot light!
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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dingo
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Re: Over Voltage

Post by dingo » Wed Mar 27, 2013 10:16 pm

No, i never did arrive at any satisfactory conclusion on that thread....so i await eagerly the resolution of your issue cause it sounds the same deal
'71 Kombi, 1600 dp

';78 Tranzporter 2L

" Fill what's empty, empty what's full, and scratch where it itches."

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drober23
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Re: Over Voltage

Post by drober23 » Thu Mar 28, 2013 7:01 am

Hey! Wouldn't you know that the wiring diagram shows 2 (!!) blue wires going to the dash. One is for the alternator idiot light, and the other is for the brake warning light. Having those mixed up would cause the brake warning light to go on when it shouldn't (which it does) and also cause the alternator light to not go on ever (which it doesn't).

This makes a lot of sense now. When the ignition is on and the engine is not running, my Brake Warning Light is on. When the engine starts, the brake warning light goes on. When the fresh air fan is on, the brake light goes back on. Somehow that fan being on changes the balance of the charges through the brake warning light.

I don't see how this would make the alternator overcharge though. Perhaps there are two issues. I suppose I will know when I sort those wires out.

I think the wires had been this way before my recent dash shenanigans, and dates back to about a YEAR ago when I replaced the dash panel with a new one (the mishandling of that is what caused my fuel gauge to fail in the first place). I have driven the bus thousands of miles (6,000?) this way.

Didn't bring the bus to work today, so I can't tinker with it on breaks. I'll look after those two wires this evening and report back. What damage may I have wrought on the bus driving it with 16v coming from the alternator? I know the radio acts up sometimes, but I haven't observed any other nasty effects other than the Propex cutting out (its upper voltage cutout is 15v).
DJ

'75 Westfalia, '79 Deluxe
(plus more busses than sense)

In a time of chimpanzees I was a monkey

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drober23
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Re: Over Voltage

Post by drober23 » Thu Mar 28, 2013 2:06 pm

This is getting weirder. I figured I would just swap in a different voltage regulator, as I had a suspected-good spare laying around. Turns out the blue wire to the voltage regulator plug is cut. This was done before I bought the bus, and I never noticed it. Time to dig through more wires until I find what is powering D+

[edit] Found the connector the loose wire is supposed to connect to. It's the blue wire connector in the right of the engine compartment. This loose end also shows 12v when the ignition is on. May be why the PO cut the connection to the voltage regulator? [/edit]

[another edit :-) ] Stripped the end of the cut blue wire to the regulator. No voltage with ignition on. 0.2 volts when first started. Once I rev a bit, it kicks in, going up to 18 V when running. [/edit]
DJ

'75 Westfalia, '79 Deluxe
(plus more busses than sense)

In a time of chimpanzees I was a monkey

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drober23
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Re: Over Voltage

Post by drober23 » Thu Mar 28, 2013 3:48 pm

Ok! Some progress.

There is power at the alternator warning light when the ignition is on, and the engine is not running. This power is coming from the brake warning light. If I disconnect the brake warning light, the alternator light comes on with ignition on, and goes out when the engine is running.

I'm still making too much voltage though. In a fit of optimism, I connected the snipped blue wire to the regulator with the blue wire dangling in the engine compartment. Still made up to 18v at the regulator plug.
DJ

'75 Westfalia, '79 Deluxe
(plus more busses than sense)

In a time of chimpanzees I was a monkey

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Re: Over Voltage

Post by Amskeptic » Thu Mar 28, 2013 4:27 pm

drober23 wrote:Ok! Some progress.

There is power at the alternator warning light when the ignition is on, and the engine is not running. This power is coming from the brake warning light. If I disconnect the brake warning light, the alternator light comes on with ignition on, and goes out when the engine is running.
Do you have a Bentley manual? Please get thee to the wiring diagram and get this car wired up correctly.

The alternator and oil pressure and turn signal lamps get their power from the ignition switch via fuse 11 I believe, a switched fuse that only powers up with the ignition switch. You do not want to be using the brake warning light switch as a power take-off. It has a completely different life going on over there.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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drober23
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Re: Over Voltage

Post by drober23 » Fri Mar 29, 2013 6:33 am

Colin,
I have a Bentley, and have been using it to diagnose the wiring. The blue wire splits in the cab. One side goes to the alternator light, and the other the brake switch. I believe it serves the same purpose in these two points, as well as at the oil switch and fresh air fan switch in the engine compartment. It tells whatever it is connected to that the engine is running.

In my case, there was power feeding back into the blue wire from the brake warning switch. I'll start on that today. The switch was wired correctly. Each wire was connected to the proper terminal.

Once I sort that out, I STILL will have to deal with the overcharging problem.

Thanks for the help so far!
DJ

'75 Westfalia, '79 Deluxe
(plus more busses than sense)

In a time of chimpanzees I was a monkey

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