Alternator Charging Gremlins?

hihorn · Posted: Sat Aug 29, 2015 1:07 pm Post subject: Alternator Charging Gremlins?

the beginning: 82 Westy Diesel,
added a 2nd battery under the rear seat. Bought a Go Westy kit to keep the 2nd battery charged, (relay with wires). As per the instructions, I tapped into the blue exciter wire off the alternator. within hours, the red alternator light comes on and never goes off, (except with the key off). I have replaced the Alternator, battery, blue wire (dash to new alternator) and a Yandina kit. Light still stays on. I'm measuring 12.3V at the alt. and at the battery. Seems to me the Exciter circuit is not working. I have run out of ideas, can someone help?
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82 Diesel Westy, Turbo Charged, ground up restoration.

airsweden · Posted: Sun Aug 30, 2015 1:11 am Post subject:

I have an 82 diesel Westy with the gowesty house battery as well. I think I have a similar alt issue too. In my case, the red alt light stays on when I start the van but if I give it a good rev... like 3-4k rpm, it goes out. I'm interested to see what can be done here as it seems gowesty's exciter kit is just for the gas powered vans. I've also replaced my alt but the light still stays on till I rev it way up.
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1982 1.6 NA Diesel Westy
1982 AHU MTDi CHC
1984 1.9 WBX Westy
1985 1.9 WBX Westy
1986 2.1 WBX Syncro Westy

RBEmerson · Posted: Sun Aug 30, 2015 7:30 am Post subject:

Check the grounds.
1) Main battery to chassis
2) Aux battery to chassis
3) Transaxle to chassis
4) Engine block to chassis
5) Ground alternator to block (at least 10 AWG wire)

Clean all of the grounds!! Take them apart, scuff them up with sandpaper, clean up the sanding with contact cleaner, tighten back up.

ADDED: The reason for adding a ground from the alternator to the block is to take care of possible resistance between the alternator case and the alternator mount. Worst case (zero connection between the case and block), that wire will carry 30-40A, so heavy wire is a must. I'd use 4 AWG if you can find a pre-made cable with tabs that will mate fully with the case ground and block ground bolts. "Close enough" doesn't get it here.

12.3V at the alternator, if it's spinning at 2K or better, is Not Good News. Check the belt tension (can't hurt, might help).

Check the field wire at the alternator - no exciter voltage, no output.

Never, ever run the alternator into an open circuit (no load). It'll cook the diodes.

But do the grounds first.
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Lord, give me coffee to change the things I can change, and wine to accept the things I can't change.

hihorn · Posted: Sun Aug 30, 2015 11:13 pm Post subject:

Thanks for the tips RBEmerson. I have checked all of those. I cannot get the light to go out even after revving the engine VERY high.
I have read all the old forums and can't find anyone else with my problem. Could the resistors on the blue circuit board behind the warning lights on the dash be an issue?
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82 Diesel Westy, Turbo Charged, ground up restoration.

RBEmerson · Posted: Mon Aug 31, 2015 12:22 am Post subject:

I guess that's possible, but generally it's best to go for the easy answers first. If you're seeing 12.3 V across the alternator while the engine's running at 2K or better, it could be the alternator itself has packed it in. Try either an alternator repair shop (they exist but can be hard to find) or grit your teeth and replace it. Or at least see if you find a loaner or something at a U-pull-it yard.

What voltage are you seeing between the field wire and ground? (engine running)
_________________
Lord, give me coffee to change the things I can change, and wine to accept the things I can't change.

crazyvwvanman · Posted: Mon Aug 31, 2015 7:30 am Post subject:

There is a 150 ohm resistor in the blue foil to power up the exciter winding of the alternator. It is physically much larger than the other resistors near it. If you look at Bentley page 90.8 it shows the early blue foil and tells which resistor is which. It is R3 for this function.

(it is wrongly descibed elsewhere in the Bentley, use page 90.8 for this)

Mark

hihorn · Posted: Mon Aug 31, 2015 8:15 am Post subject:

Thanks Mark, I'm off to Fry's to buy some resistors. AND I'll pull the Alternator and have it tested yet again. Thanks.
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82 Diesel Westy, Turbo Charged, ground up restoration.

crazyvwvanman · Posted: Mon Aug 31, 2015 8:27 am Post subject:

There is a test in the Bentley for the charging excitation resistor in the dash cluster. The test doesn't mention that it is for the 150 ohm resistor but that is what it is for. That is because VW doesn't consider the resistor a replaceable part, just the complete blue foil if the ohm test fails. This resistor is in parallel with the charging warning led and this bypass resistor is the path of most of the excitation current, not through the led itself. So the led can seem to work but if the bypass resistor is burned out most of the alternator excitation current will be missing.

Note that the test pins shown are only for 80-84 clock clusters. Tach clusters and 85+ clock clusters use the pins in my handwritten note on the page.

Image may have been reduced in size. Click image to view fullscreen.

Mark

RBEmerson · Posted: Mon Aug 31, 2015 9:08 am Post subject:

Strictly from a troubleshooting standpoint, read the field voltage before opening up the gauge cluster. If the field voltage is good, but there's no output voltage, that rules out the resistor. OTOH, if there is no field voltage, by all means, trace the wiring back to the gauges.

My point is it's easier to check the field voltage than the gauges. If it turns out that the resistor is OK, you've spent time and effort on something more difficult than waving a voltmeter around. Or, put another way, KISS Wink

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Lord, give me coffee to change the things I can change, and wine to accept the things I can't change.

crazyvwvanman · Posted: Mon Aug 31, 2015 10:26 am Post subject:

Agreed, voltage testing at the alternator D+ should come before any fooling around with the cluster.

Things are slightly complicated by this being an 82 diesel van. The 65 amp alternator uses a single 3 pin spade connector for all connections. This also makes substituting another VW alternator slightly more work but I'd get rid of the 3 pin alternator setup if it was me. Also it makes some of the battery cable suggestions moot since the battery is back next to the alternator and the negative battery cable grounds to the engine rather than to the chassis.

Mark

hihorn · Posted: Mon Aug 31, 2015 12:20 pm Post subject:

It looks like I am looking for a new blue foil for my 82. Everything tested good until I got to the resistor. Upon removal I see it's physically burned. VW crimps the resistors to the circuit board making removal without damage to the blue foil next to impossible. BTW, I upgraded to a Bosch 90 amp alternator with post wiring. I also fabed a new alt. to battery cable. The old plug is going up for sale to help off-set the cost of a new blue foil.
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82 Diesel Westy, Turbo Charged, ground up restoration.

crazyvwvanman · Posted: Mon Aug 31, 2015 12:32 pm Post subject:

Ok, for a replacement foil you need one from a pre 1985 clock cluster. There is also a single wire change after 82, when VW moved the glow indicator wire to a different pin on the 14 pin connector for 83/84 foils.

If you are in SoCal I could probably help you with a replacement foil.

Mark

RBEmerson · Posted: Mon Aug 31, 2015 4:01 pm Post subject:

Is there any way to solder to the remains of the resistor? I know soldering to foil is a good way to ruin the foil without getting anything good out of it.
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Lord, give me coffee to change the things I can change, and wine to accept the things I can't change.


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