engine and drivetrain Not Charging

[Orusty2]

My newly acquired 76 02 has the L light on but its very dim you cant see it unless its dark -the car is not charging

what i have done

-Local altenator shop checked alternator its good

-I cleaned all the connections on the alternator

-I hooked up a jumper wire on the connector for the voltage regulator the light gets bright red

-While car is running battery reads 12.62

- I cleaned and sanded the 3 prong connector that goes into the alternator

- I sanded the ground strap where it connects next to the relays in the engine bay

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Ran out of time earlier I did not:

-clean the brown ground wire where it connects to the front of the engine(comes from alternator 8mm nut hold it on)

-Clean the ground strap where it connects to the block

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could the 3 wire plug in the back of the alternator be corroded under the rubber?

any suggestions..

thanks in advance

[SteveJ]

To eliminate the wiring harness, run some seperate wires to the ground and the V-reg. Just use some 14-16 guage wire and crimp on some 1/4" female quick-connects. Double check the colors of the wires to make sure nothing gets reversed. This will at least determine/eliminate if there are isues in the wire harness.

Possibly check the connections for the back of the instrument cluster. Could be the round multi-pin connector on the back is corroded.

What voltage do you read at the battery terminals with the motor rev'd up to 2000rpm or so? Should be closer to 13v, maybe a bit more.

Battery terminals clean?

[Orusty2]

when the car is reved up the voltage at the battery goes down not much to about 12.4

also the l light does not fluctuate with rpm

i will try the seperate harness later can that be explained with detail?

im not sure which wires would go where?

battery teminals are clean

its a brand new battery that is now drained i have to jump start the car every time for testing i dont have a charger

[Orusty2]

also the car will remain running even with a dead battery it made a 90 mile trip when i bought it

[SteveJ]

If you look at the connector on the bottom of the V-reg, you will see it is an upside down T shape with three spades that slide into the the wire connector. Look on the back of the alternator and you will see the same type of connector.

There are three wires in that harness. At one end of the cable, one of the wires has a tap running off of it. This is the wire that runs to your test plug in the engine compartment and then on to the charge light in the dash.

Pull the connector from the V-reg. See what color wire is at the bottom of the T. Pull the connector from the back of the alternator and you should see the same color wire in the same position. Using a seperate legnth of wire, crimp on some quick connects. Place this wire from the alt to the Vreg. Do the same with the other contacts until you have three wires in place.

Now, remember that one of those wires in the harness goes to your charge light. You will need to add a pigtail (two wires in the same crimp on connector) to one of the wires. Connect that wire into the connector of the plug that has two wires on it.

It sounds like a lot, but it's not that much to do this.

One thing I remembered- how is the belt tension? A loose belt could cause an underperforming alt.

[Orusty2]

Just did one more test on the alternator its reading 12.5 volt meter to b+ on altenator -ground to body of alternator with the eninge at about 1500rpm

Yesterday i had it benched tested and it was reading upwards of 15 because it didnt have a regulator on it

??????

[eastsidebimmer]

I had a similar problem so I ordered a new 14V regulator from the dealer. This worked fine for me. http://www.bmw2002faq.com/component/option,com_forum/Itemid,57/page,viewtopic/t,363317/

[02for2]

The Bosch alternator is spec'd at 13.5-14.5 VDC. If you're seeing more on a bench test, it's a problem.

Suspect the voltage regulator, but also don't rule out the battery either. A cracked cell or broken and/or sulphated plate(s) can mask themselves as charging issues.

If the battery is 5 years old (or of unknown age) pitch it.

Cheers!

[c.d.iesel]

replace the alternator - you have bad diode(s) - really

[Guest Anonymous]

definitely pull the 3 prong connector from the alternator and make sure the connections are good and that the wires are firmly seated in it.

[Orusty2]

CD. My alternator was bench tested and was putting out plenty of volts

Even if its putting out 15+ volts could the diodes still be bad ?

[Orusty2]

Ok so my alternator is shot if its reading more than 15v?

Why is the charging light on? And loosing charge ? If its putting out so many volts?

Battery is brand new but now dead I have been jump starting the car each time to check things with the voltmeter

I put a jumper wire on the voltage regulator plug and the L light did not go out regulator ok?

[c.d.iesel]

bad diodes

[Orusty2]

oh now i see bad diodes

thank you... i will be replacing the alternator