Alternator. ...no output.

[kevtherev]

OK
I have a constant ignition light
I have checked output from the alternator

zero

So I changed the brush pack for a known working unit

Zero

Is there anything else I can do before its condemned?
Bear in mind I have limited tools and access to spares.

[ghost123uk]

There is little else that can be easily changed in an alternator, so sadly I reckon you need to look for a replacement.

Billy739 on here often has used spares like this.

[bigherb]

Ignition light on, With just the engine running or with the ignition off as well?
Have you checked the alternator connection on the starter motor?
Is the contact spring making good contact with the regulator pack?

[kevtherev]

Thanks guys...

It was the diode plate that went baps up.
Thanks to some prompt posting from club members I had a new one in my hands the very next day.
The guy who sold it was quite amazed.. he said it had been sitting on the shelf for 15 years, he was glad to see it sold so I had it for £50. plus my old one back

The fella's shop is Alter-start in Barnstaple.. decent chap with a wealth of starter and alternator knowledge.

[CovKid]

Isn't £50 a tadge steep or am I missing something here?

[kevtherev]

Brand new Bosch 55 amp Alt no exchange is that steep then?

[CovKid]

Ah, you didn't say that. Your post infers you just replaced diode plate

Got a diode plate 'ere you could have had for £49.99 our kid

[lamb125]

Sounds like I have a similar problem looming. On our way back from a camping weekend in Swanage a few weekends back I noticed the battery light flickering. At times full on, then out, then flickering, but generally flickering.

Battery seems strong enough to start the van ok, but have noticed the wipers are moving much more slowly than normal. The needle on the Volt meter is hanging around 12V.

Someone told me that sometimes it's just the regulator (fixed by 2 screws on the alternator) that is at fault, but I'm unsure where to start, how to test,etc.

[kevtherev]

The brush pack on the back of the alternator is a cheap component (£15)
I replaced mine with the spare I carry
this failed to cure the flickering batt light.
This went on for a month getting no worse, but complete failure was around the corner
I foolishly ignored the warning
the new alt has stopped the flickering batt light and has revitalised the starter battery!

Alternator failure can be one of four things I think
regulator brush pack
diode
windings (rare)
bearings. (noise)

All the items can be bought and replaced.
With my old alt I shall repair it and save a mint.

[lamb125]

I had someone at work check it out at lunchtime, established that the regulator is doing its job. Probably going to remove the alternator and check the brushes. Weirdly though, despite not disconnecting a thing, I turned the key and nothing!! Battery is showing about 11.5v

[lamb125]

Following a 3 hour ish charge the battery turned the engine over, but when the neg terminal was pulled off the engine promptly died. I can only assume that the electrics to spark the plugs etc are running off the juice from the battery and not from the alternator which would confirm that the alternator is indeed dead!

Does that make sense?

[kevtherev]

D

I had someone at work check it out at lunchtime, established that the regulator is doing its job

what was the output from the alternator with the battery lead disconnected?
should be over 14 V

[lamb125]

Not sure, it's off the van and at work for inspection/test now. The brushes protrude about 2 to 3 from the regulator hsg, should they spring out further?

[Oldiebut goodie]

This may help:
DIODE ASSEMBLY
1) Place ohmmeter on x 100 scale. Connect ohmmeter leads
across "B+" terminal and 3 stator terminals one at a time. Reverse
leads. Ohmmeter should indicate continuity in one direction only.
2) Connect ohmmeter leads across negative plate and 3 stator
terminals one at a time. See Fig. 1. Reverse leads. Ohmmeter should
indicate continuity in one direction only.
3) Connect ohmmeter leads across "D+" terminal and 3 stator
terminals one at a time. Reverse leads. Ohmmeter should indicate
continuity in one direction only. Replace diode assembly if defective.
ALTERNATOR & REGULATOR - BOSCH
Article Text (p. 3)
1991 Volkswagen Vanagon
For Volkswagen Technical Site
Copyright © 1998 Mitchell Repair Information Company, LLC
Saturday, March 18, 2000 09:00PM
Fig. 1: Bosch Diode Assembly Test
Courtesy of Volkswagen United States, Inc.
STATOR
1) Place ohmmeter on lowest scale. Connect ohmmeter across
stator leads. Resistance between leads should be approximately .14-.15
ohms for 55-amp alternator and .09-.10 ohms for 65 through 90-amp
alternators. If resistance is incorrect, stator has open or shorted
windings and must be replaced.
2) Place ohmmeter on X 1000 scale. Connect ohmmeter between
stator core and stator lead. No continuity should exist. If continuity
exists, stator is grounded and must be replaced.
ROTOR
1) Place ohmmeter on lowest scale. Connect ohmmeter across
slip rings. Resistance should be 2.8-3.1 ohms for 65 through 90-amp
alternators.
2) If resistance is too low, rotor has short circuit and must
be replaced. If resistance is infinity (no continuity), rotor has open
circuit and must be replaced.
3) Place ohmmeter on x 1000 scale. Connect ohmmeter between
either slip ring and rotor core. No continuity should exist. If
continuity exists, rotor is grounded and must be replaced.
4) Clean slip rings using fine sandpaper. Rings which are
worn or pitted should be turned on lathe. Minimum ring diameter is 1
ALTERNATOR & REGULATOR - BOSCH
Article Text (p. 4)
1991 Volkswagen Vanagon
For Volkswagen Technical Site
Copyright © 1998 Mitchell Repair Information Company, LLC
Saturday, March 18, 2000 09:00PM
1/16".
5) If slip rings are beyond repair, remove rear bearing from
slip ring end of rotor. Unsolder wires from slip rings and bend up
ends of rotor winding. Pull off slip rings. Ensure ends of rotor
winding are not damaged.
6) Insert ends of rotor winding into slip ring and press new
slip ring onto rotor. Slip ring end must be 9/64" from end of collar.
Solder rotor winding to slip ring terminals. Turn rings on lathe and
retest rotor. Maximum slip ring run-out is .0012" (.03 mm).
BEARINGS
Always replace bearings. If replacement front bearing is
sealed on one side only, open side must face rotor. If replacement
rear bearing is sealed on one side only, open side must face away from
rotor.
BRUSHES
Ensure brushes are longer than 7/32". Replace if necessary.
Unsolder brushes from voltage regulator. Solder new brushes. Do not
allow solder to run into strands of brush leads. Brushes must be free
to slide in brush holder with normal spring tension of 10-14 ozs.
(283-397 g).

[lamb125]

Many thanks for that info. Just located an identical regulator with healthy looking brushes amongst a pile of spare alternators in our stock room. Will be refitting the unit at lunchtime so will let you know how I get on.