charging/alternator thread*more confused than ever*

[Smokey Eddy]

I searched for advice on replacing alternators and charging dead batteries with the alternator and found nothing. So here goes...
I replaced my alternator due to burnt diodes and am left with a very dead, <half a year old battery. I changed from a 65 amp to a 90 amp and got a jump start from a friend. Her car was charging at about 13.2v. When I pulled the cables off my battery V dropped to 10.8v. So I connected them again and reved it good n proper. My make shift multimeter now said 14.0v steady. I took the cables off a second time and it held 14.0v. I waited about ten seconds. Turned my meter off and on again (IT crowd reference) and it still said 14 so I thanked my friend and she went on her way. No less than 5 minutes later I noticed the lights were dim. The voltage was so low now on my battery that my meter couldn't read it.
So my guess is that my battery I have now is too dead to give the alternator the minimum 12.6v required and I need to charge it first my other means.


I also couldn't help but notice the battery light never came on even when the car was dead? The glow plug light came on and off a couple times though.

EDIT: I now know that my old alternator did not have burnt out diodes. The flickering battery light had to do with the build up to what ever issue im experiencing now.

[bajacalal]

1. It is possible to kill a battery by leaving it uncharged for long periods. It might not work again, ever.

2. It's really not the best idea to charge your battery from a completely dead state using only your alternator, especially a relatively small alternator like the 65 amp. It's a lot of load on that alternator, try to use a battery charger if you can, some parts shops around here will charge it your you for $5-10.

3. Try to find a high frequency battery charger if you can. That means it actually delivers high frequency electrical pulses to the battery while charging it. That helps knock off some of the deposits that build up on the lead plates which kill the battery, so they sometimes work to restore a battery that is otherwise bad and will not charge.

4. The way the battery light works is that it is connected through the alternator exciter wire. Being that it is a light-emitting diode electricity will only flow one way through it, which is when the alternator is not charging. If your exciter circuit is not connected, or not working, the battery light will not come on at all, even when the key is ON but the engine is OFF. Make sure the exciter circuit (usually a blue wire) is providing battery voltage to the alternator when the key is ON, engine OFF. It is necessary for the alternator to work and charge properly.

edit: I've also heard conflicting stories about repeatedly disconnecting your battery cables while the car is running. Some say it can kill your voltage regulator, which would leave you with no alternator output.

[BigVWman]

I would say you have at least one issue maybe two. The first is once the car starts its designed to run off the alt not the battery so somewhere your charging system is amiss if dropping from 14 down to 10 and change with no additional load. I would agree with above check that blue wire and make sure battery light comes on with key only and goes out after the engine starts. If you never see it even with the key on track the blue wire for continuity. The second issue could be a dead battery though its tough to say. 10. anything is pretty low for a charged good battery but if it were still discharged can't really tell. Just my 2c.

[Smokey Eddy]

Ok. I've bought a battery charger (canadian tire had a 2/20/55/150 amp for 50% off) so once the battery is charged I can drive back an hour to my real multimeter. Put it on charge and trouble shoot. Thanks so much for the input.

Here is a question, what if I'm not getting voltage from my blue "charge now" wire? What do I do then? I've replaced the connections on all the wires but its still the original wire.
Prior to my old 65 amp (i just bought a 90) breaking the battery diode would very dimly glow and sometimes come on periodically.
I'm going to go re-clean all the contacts I think. Paying special attention to the grounds...

[theman53]

I always have run an extra ground from the battery to the alt. I usually never have any problems with grounding.

[bajacalal]

Here is a question, what if I'm not getting voltage from my blue "charge now" wire? What do I do then? I've replaced the connections on all the wires but its still the original wire.
Prior to my old 65 amp (i just bought a 90) breaking the battery diode would very dimly glow and sometimes come on periodically.
I'm going to go re-clean all the contacts I think. Paying special attention to the grounds...

Then you need to trace the source of the problem back to the dash/cluster/ignition. Is anything else not working?

Alternatively, you can just run a new wire to it. It needs switched 12 volt power (it will drain the battery if directly connected). 

The very faint alternator light glow that you can see on a dark night is caused by the alternator path to ground not being a perfect conductor compared to  the the rest of your electrical system. I don't believe it's a problem but perhaps you could directly ground the alternator anyway.

[8v-of-fury]

The very faint alternator light glow that you can see on a dark night is caused by the alternator path to ground not being a perfect conductor compared to  the the rest of your electrical system. I don't believe it's a problem but perhaps you could directly ground the alternator anyway.

Hmm, I don't know if I agree. I have a perfect alt-engine ground and a perfect engine-battery ground. Yet I still sometimes see the faint glow, it must be something else.

Now when I say perfect, I mean filed down perfect clean metal to clean metal connections with die-electric grease on them. Even the alt-bracket connection.

[Smokey Eddy]

This is all very good stuff. I'll add a ground ( I have about six coming off the negative terminal of the battery Haha!) I do only have one big one however going from a tranny to block bolt and another big one going to the body and then another big 4ga ground going up to the dash/amplifiers.
So ill charge the battery up, ground the alternator directly AND re-wire the blue wire. Could it use the stop solenoid circuit?

[mtrans]

I have been there
Try with well KNOW good acu,after start see voltage.
With old,bad acu, if you start engine turn on some lights and take off + from acu,if he still work put more load and see what you see,some LOAD MUST be on BEFORE take off +.
If ground is OK look like it`s bad acu.
This is for old car I never try on new comuter car

[damac]

I got my jetta used a year and a half ago.  Things seemed to work ok so I didn't touch things much until the need arose.  One day the battery was getting low during a drive and wouldn't restart the next time.  Checked alternator and battery out and both were bad. 

I was also sometimes getting wierd tach bounces and that faintest of glow of the charge light that I noticed at night.

I found at first in the stock loom there was a couple connectors near the battery that then made their way over to the alternator, near the fan.  Those connections were kind of loose so I cut that out and made my own connectors.  Helped in that moment but noticed the same thing happen again later.  Then I did a continuity test and would get wierd things depending how I jiggled things.

So I just cut off the whole loom up past the battery and ran new wires from that point to their destination in my own protective cover and my car has never done it since?  My tach works whether cold or hot, and my charge light goes off after the first rev of the day.

Only other time I have seen my tach react differently now is if the headlights are on but I imagine that is some vw thing, it seems to settle right back in with correct readings when the car is warmed up and the throttle has been blipped.

I looked at the old wires and the loom was rock hard in front of the fan and spots of the wiring were frayed.  Perhaps all those heat cycles in front of the fan leads to eventual breakdown.

I also have all new larger grounds, also added one to starter mount bolt hole and alternator for the heck of it.

[Smokey Eddy]

damac, Sorry what do you mean by loom? which ones? can you be more specific?
mtrans, I don't understand most of what you said. What is acu?

For some history on my problem the battery is say 6 months old at most and the alternator is brand new (was an attempt at fixing this problem)

I just jumped the blue wire (which i have connected to the post beside the big B+ post that goes straight to my battery) to the fuel shut off and of course i couldn't turn the car off after that but that means the blue wire is getting power.
Im wondering if maybe i mixed up the blue/black and red/black connections and they should actually be reversed?
Can someone confirm this? I have wired it correctly as per the bosch pamflet it came with but someone with a working system would ease my mind a lot more.

I'm going to run a 12ga wire from the body of the alternator straight to the battery and see if that solves anything. I'll also do some tests for continuity and so on. key off, key on, running blah blah blah since I finally found my multi-meter in one of my suitcases.

I'm also going to remove, clean & coat with di-electric grease:
the ground from the battery to the trans/block bolt
the ground to the body
the ground that i have going to the dash (clean it at the battery)
the power wire from the battery to the starter solenoid
the wire coming from the big B+ post on the alternator to the starter solenoid

I'm going to clean them with vinegar if i've got it. (dont have any sand paper for files on hand)

On a side note i noticed some odd behavior possibly worth mentioning. While driving with a freshly charged battery the battery light in the dash would glow dimly and go out and then again and again slowly growing stronger and stronger with the glows.
When the battery was truely dieing and the head lights were dim and the wipers didnt work and so on I noticed the battery light was no longer  coming on.
As a test (I had my sockets with me at the store parking lot) I took off the blue wire which caused the battery light to come on while running. - This leads me to believe that perhaps the red and blue wires are switched because I was under the impression that function was the purpose of the red and black wire?

[Smokey Eddy]

Here's the data.
At the red wire where i have it now on the alternator i get 8.77v when running.
At the blue wire (and everywhere else) while running i saw and astonishing 16.99V (I had my charger connected to it charging at 12.5v at 20amps for maybe a total of 15 minutes). turned out my multimeter is faulty. Really reads 11.9V

With the key in the "on" possition without starting I saw 0.02V at the blue wire and 0.02V at the red wire.
The battery with the engine off showed 17.00+v... this puzzles me a great deal

While running the battery light was dimly glowing.

I tried grounding (with a spare length of wire) the alternator to the battery, the battery to the body.

I did a continuity test all over and saw numbers no greater than 0.002 on my multimeter. Most were 0.001 (0.000 being zero resistance). I cleaned and greased all connections anyways - this made no difference.

I noticed one connection i must have replaced years ago that leads to the dash that had a bit of corrosion in the connector - Perhaps this is a culprit?

I have a couple questions; What is causing this incredibly high voltage? Why wont' the alternator charge!!! What is causing that light to glow in the dash? Can a bad battery cause high voltage problems? Can high voltage problems lead to charging problems (i would imagine this would conflict with the voltage regulator built into the alternator)? Can this undoubtably damage my new alternator?

[8v-of-fury]

Jfc. That is a nightmare lol.

If the alt is new and the battery new.. I cant see what the problem would be here.. but 17v at the battery!? right after hitting it with 20a though right??

[Smokey Eddy]

Well, I must be honest, the battery isn't BRAND new... it's been dealing with this charging issue so it's been drained (not to dead but to the point where it wont start the car) about 4 times. Had the water topped up twice - last time i did it i over filled a bit and lost some acid in the process.

I juiced it good for about 15 minutes at 20amps and then gave it a 10 second fry at 150 amps and when the count down got to zero i started the car and then did my tests.

For running at 17 volts the head lights were surprisingly dim...

[8v-of-fury]

If it has sat dead in the cold and allowed to freeze I do fear it may be toast.. *** son.

Dont suppose you have a friend who would be willing to lend you a battery for a little why for you to run the tests with a different battery in there?