'75 Westy Alternator Dash Light Function

dingo · Post by **dingo** » Fri Jun 19, 2009 1:22 pm

I'm having charging/regulating issues and I'm trying to figure out the function of the alternator dash light.

According to the diagram it is grounded(?) at the instrument panel and gets 12V from some heater relay(?) when the ignition is turned on? So what is its actual function and how can I test?

Post by **Amskeptic** » Fri Jun 19, 2009 2:10 pm

dingo wrote:I'm having charging/regulating issues and I'm trying to figure out the function of the alternator dash light.

According to the diagram it is grounded(?) at the instrument panel and gets 12V from some heater relay(?) when the ignition is turned on? So what is its actual function and how can I test?

It gets 12volts at the dash through its shell, like the oil lamp. The center wire is the "ground" like the oil lamp as well. When the alternator is off, current flows and the lamp illuminates. When the alternator is putting out, you have 12 volts at both sides of the lamp filament and thus it goes off.
The lamp has to be good in order for the alternator to put out, because the lamp illumination circuit is also the "excitation circuit" to get the field windings magnetized.
Colin

dingo · Post by **dingo** » Fri Jun 19, 2009 3:11 pm

Amskeptic wrote:
dingo wrote:I'm having charging/regulating issues and I'm trying to figure out the function of the alternator dash light.

According to the diagram it is grounded(?) at the instrument panel and gets 12V from some heater relay(?) when the ignition is turned on? So what is its actual function and how can I test?
It gets 12volts at the dash through its shell, like the oil lamp. The center wire is the "ground" like the oil lamp as well. When the alternator is off, current flows and the lamp illuminates. When the alternator is putting out, you have 12 volts at both sides of the lamp filament and thus it goes off.
The lamp has to be good in order for the alternator to put out, because the lamp illumination circuit is also the "excitation circuit" to get the field windings magnetized.
Colin

Well I'm slightly less confused. So the instrument shell should show 12V with ignition on, and the blue wire should show variety of smaller voltages at ignition-on, and more voltage at engine on.

I assume by good order, you mean 'it glows'.

Alright, thanks. I'll do some more tests and get back.

dingo · Post by **dingo** » Fri Jun 19, 2009 3:39 pm

O.K. I got my dash light working. It doesn't glow when connected to the VR and the ignition is on, but here is where its gets insane. Where is the black wire supposed to go? The diagram shows TWO black wires, one to ground and the other to W1 H6. WTF? So one of these wires, with the ignition switch ONLY on in 1st position, I got the blown-spark-plug-wire type shock through my finger and came out my other hand. Engine was not on.

dingo · Post by **dingo** » Fri Jun 19, 2009 7:41 pm

...also, where and how is the alternator actually grounded?

dingo · Post by **dingo** » Sun Jun 21, 2009 4:41 pm

O.K. I've tried a replacement regulator and I still get the same symptoms.
Symptoms are: Start engine. Charge slowly moves up from 13..14..15...if i pop the throttle just slightly it goes up to 16 V..17 V etc. I shut the engine off as this cant be good.

Any ideas ? I'm baffled. By the way, this is an external regulator setup.

P.S. The dash idiot light comes on and goes off at the correct times.

I've had a 'bad diode' scenario before, and in that case, you still get a charge, but a reluctant 13...13.5...But in this case I'm getting WAY too much.

RSorak 71Westy · Post by **RSorak 71Westy** » Mon Jun 22, 2009 7:56 am

Yes you're overcharging. The voltage regulator isn't cutting the power to the field of the alternator. You have a wiring issue.

Post by **Amskeptic** » Mon Jun 22, 2009 8:06 am

Sorry I have been absent. I am in the wilds of Oregon.

Those black wires goes to insulated plates on the cluster so that the gen/oil idiot light sockets are live. Black is live ignition with VWs.
Colin

dingo · Post by **dingo** » Sat Jun 27, 2009 10:17 am

Amskeptic wrote:Sorry I have been absent. I am in the wilds of Oregon.

Those black wires goes to insulated plates on the cluster so that the gen/oil idiot light sockets are live. Black is live ignition with VWs.
Colin

Thanks for the reply. The idiot light functions as it should: ON with 12V/2V, then OFF with 12V/12V.

The black wires I was referring to were the two black wires in the schematic that depart from the alternator. One goes to ground, the other goes to the test connector. Seems like a stupid color to use because it carries 12V.

Anyways. I've eliminated those issues. I guess I will try a third regulator, and then another alternator, although this one definitely is charging as it should in a raw, unregulated state.

dingo · Post by **dingo** » Mon Jun 29, 2009 9:41 am

I found a Bosch manual on charging and regulation.

http://itinerant-air-cooled.com/album_s ... user_id=15

jblair630 · Post by **jblair630** » Mon Jun 29, 2009 1:07 pm

It gets 12volts at the dash through its shell, like the oil lamp. The center wire is the "ground" like the oil lamp as well. When the alternator is off, current flows and the lamp illuminates. When the alternator is putting out, you have 12 volts at both sides of the lamp filament and thus it goes off.
The lamp has to be good in order for the alternator to put out, because the lamp illumination circuit is also the "excitation circuit" to get the field windings magnetized.
Colin

Just out of curiosity, is this true for generators as well as alternators?

dingo · Post by **dingo** » Tue Jul 07, 2009 3:52 pm

A long strange trip, but I finally resolved the wild overcharging issue. Insufficient grounding through the alternator. So the regulators were all fine after all.

dingo · Post by **dingo** » Wed Jul 08, 2009 10:52 am

Battery condition..

before you start engine....

Bleed surface charge from battery by turning headlights on for 1 minute

then measure across battery

12.6 to 12.72 100% charged
12.45 ........75%
12.30 .........50
12.15 .........25

To check charge rate....

engine running
With volt meter +ve on battery and other lead to earth
Headlights on high beam etc, the alternator should
"maintain at least 12.6 Volts to 13.6 V at 2000 RPM" (not drop below 12.6V)

and with no load between 13.6V - 14.3V

To check diodes...

with engine off
To check alternator for diode leakage, disconnect B+ lead to battery +ve and place meter (set on Amps) in series between B+ and +ve terminal of battery - should not read more than 0.5 milliamps -

with engine running:
switch meter to read AC, connect meter lead to B+ and other lead to a good ground.
should not read more than 0.5 VAC - higher indicates damaged diode(s)

dingo · Post by **dingo** » Sun Jul 12, 2009 8:54 pm

Still having overcharging issues, so this points to internal grounding gone haywire.

Is there an actual physical wire from the alternator to ground? The wiring schematic shows one, but I have not located it so I don't know if it exists or if they are just assuming that the engine is grounded to the chassis.

dingo · Post by **dingo** » Sun Jul 12, 2009 9:19 pm

Just in case someone stranded in Burkina Faso or Surinam is actually reading this thread, this is what i discovered:

These alternators are type 'B'. One brush to the field (DF), one brush is grounded to the alt (D-) and the third terminal (D+)is connected via (in my case very cracked and brittle wire) to the diode pack. This terminal is labeled 3.4 for as yet unknown reasons.

My unusable spare alternator has the brush disconnected from its ground strap. I'm guessing this is the fault. I will find out if this is the case after extraction.

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'75 Westy Alternator Dash Light Function

'75 Westy Alternator Dash Light Function

Re: '75 Westy Alternator Dash Light Function

Re: '75 Westy Alternator Dash Light Function