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charging, alternator, etc problems

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a few weeks ago steve was out in the o2 truck...the alternator light came on and stays on except for an occasional flicker off...

i picked up another alternator (used) steve took it to autozone to test before installing it and it tested good

replaced the original with the new, used alternator but have the same symptoms..."O" light stays on except for occasional flicker

he changed belts, added a new ground from alternator to engine block none help'd...the just charged battery is just above 12V but the alternator only shows an output of approx 10V

what else might we look at

https://www.google.com/search?hl=en&q=site%3Abmw2002faq.com+bad+voltage+regulator&sourceid=navclient-ff&rlz=1B3MOZA_enUS348US348&ie=UTF-8

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search! oh wait, you did....;-)

seriously...is the alt a new style with regulator internal or is it the old style with external reg?

have you checked all the connectors and wiring for cracks and breaks?

alt won't work without a solid circut for the warning light. check that wiring path closely.

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search! oh wait, you did....;-)

hard to believe huh...?

seriously...is the alt a new style with regulator internal or is it the old style with external reg?

it's the old style with external regulator

have you checked all the connectors and wiring for cracks and breaks?

yes sir, all wires & connections appear to be good

alt won't work without a solid circut for the warning light. check that wiring path closely.

have not checked wiring at lights and/or gauges

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have you checked all the connectors and wiring for cracks and breaks?

I had similar symptoms on my tii using the original externally regulated alternator. Turned out that the main Red (+) wire to the alternator was toast where it connected. Everything looked good from the outside, but the wire was toast on the inside. I removed about two inches from the end of the wire and spliced/soldered in a new piece and a new ring connector. Problem solved. HTH

John

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A fellow had a similar issue a few years ago at the vintage (like John mentions above) and with some moving wires around, Mike Pugh found some sparks from the red wire connection to the alternator. Made a good termination and all was well.

Also, replace the voltage regulator if the red wire proves ok

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I had similar symptoms on my tii using the original externally regulated alternator. Turned out that the main Red (+) wire to the alternator was toast where it connected. Everything looked good from the outside, but the wire was toast on the inside. I removed about two inches from the end of the wire and spliced/soldered in a new piece and a new ring connector. Problem solved. HTH

John

john...he just swap'd a known good regulator off of my 76 and even though the wire look'd good he unwrap'd the wire from alt to battery, checked it and added new terminal ends at alt & battery

no luck

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Check the battery. 12 v means dead. Should be 12.6 at rest. At 12.5 you're gonna start seeing problems.

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Check the battery. 12 v means dead. Should be 12.6 at rest. At 12.5 you're gonna start seeing problems.

i don't have a digital meter that shows 10ths or fractions of volts but the one we use shows the battery at slightly above 12V...same reading as my 76....i'm just guessing of course but my guess is the slightly above 12 v's puts it right at 12.6

the battery is brand new but not knowing the problem, it very well could be a battery gremlin...except we've also tried several other good batteries getting the same readings and results

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" Everything looked good from the outside, but the wire was toast on the inside. I removed about two inches from the end of the wire and spliced/soldered in a new piece and a new ring connector. Problem solved. HTH

John"

This ^^^^^

It also applies to the 3 wires that plug into the back of the alt & also plug into the regulator.

Visually may look OK, but can have corrosion or stranded wires breaking under the insulation right behind the terminal.

Also make sure the 3 female terminals inside the plug that plug into the back of the alternator are tight. You can wiggle one out & replace just one, if need be. New terminals are the

.250 inch variety sold at local hardware stores.

The alternator puts out zero without a solid working connection to the regulator.

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A quick way to test the alternator is to disconnect the 3 wire connector at the alternator. Then, with the engine at 2000 RPM or more, make a connection (at the alternator) between the terminal marked DF (black field wire) and the terminal marked D+ (blue wire). This fully energizes the field coil if the alternator is functional and it should put out all it's capable of. If this turns out OK, plug the connector back into the alternator and disconnect the plug from the regulator. Again with the engine at 2000 RPM or more, make a connection between the black and blue wire at the regulator connector. You should again see full output from the alternator. If you don't, one of the 3 wires connecting the alternator to the regulator is bad or not making contact.

Good luck.

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A quick way to test the alternator is to disconnect the 3 wire connector at the alternator. Then, with the engine at 2000 RPM or more, make a connection (at the alternator) between the terminal marked DF (black field wire) and the terminal marked D+ (blue wire). This fully energizes the field coil if the alternator is functional and it should put out all it's capable of. If this turns out OK, plug the connector back into the alternator and disconnect the plug from the regulator. Again with the engine at 2000 RPM or more, make a connection between the black and blue wire at the regulator connector. You should again see full output from the alternator. If you don't, one of the 3 wires connecting the alternator to the regulator is bad or not making contact.

Good luck.

thanks a bunch...we'll try that....on that subject my next question was wire related...

although they look'd green to me, they probably are blue in a brighter light than when i looked but...

the plug on the alt has a black, red and blue wire....

the plug on the regulator has a black, red and 2 blue wires...

i can't trace them or follow their paths without cutting the loom but i assume those are the connection between the alt and reg...then one of the 2 blue wires from the reg goes to places unknown to me

am i correct

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this may seem to be basic but i would look for resistance in your wiring. disconnect it from the alternator and the next connector that those wires go to. If you have a DVOM(digital volt/ohmmeter) handy then you can check resistance between the wires. if not then head down to harbor freight and get one, they are cheap but they work for what you need. hope this helps, usually anything about .5ohms is gonna be considered high resistance for wiring.

Hope this helps,

Brandon

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1 blue wire at the regulator connector goes to the alternator, the other goes to the dash-light. When you test the wires to the alternator, wiggle them to see if anything changes.

These wires obviously flex a lot when the car is running, so breakage inside the insulation is very likely.

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Guest Anonymous

+1 on checking the blue wire connection on the back of the alternator. If it is loose, the dash light will glow dimly at low rpms.

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