Battery Dying?

[air-cooled or diesel]

dont quote me on this but isnt the red wire to idiot light? if thats disconnected you dont get a proper charge.

[82vdub]

I see two wires connected the the alternator in that pic. The big fat red wire goes directly to/from the battery, and at some point, the inside of the car to the fuse panel to run the electrical system for the vehicle. The blue wire, I believe, is what goes to the idiot light on the dash. The black/red wire coming out of the wiring harnass I don't see connected anywhere to the alternator. This is where a Bentley manual will go a long way to tell you what color wire goes to where.

My alternator idiot light functions just fine 99.9% of the time, but there is the occasion where it doesn't illuminate when I turn the key on, and if I start the car, the battery won't charge, and my idiot lights won't tell me it's not charging either. If I cycle the key a few times, I do get that idiot light to come on and then I know I can start the car and drive away. If everything else ends up being just fine, pay close attention to this when you start your car. I rigged up a voltmeter so I could tell when the car is charging, irregardless of what the idiot light does or doesn't say.

[StevenPH]

The small red/black wire does connect to the alt, just outside of the picture, to a tab connection with a W marked under it.

I'll check bentley again too to see what i can find.

[82vdub]

The W terminal on the alternator has something to do with the tach, or the 2000RPM oil light thingy, something along those lines. I believe it's the blue wire that goes to the idiot light. At least that's what I remember for my gas Jetta.

Also see my first post on what I ran into on my gas Jetta.

viewtopic.php?f=8&t=12225&p=86212

[Fatmobile]

I suggest getting a dash-mounted voltmeter.

Also there is a connector under the battery. It splices the blue wire and commonly corrodes.
It could cause an intermitant problem.

Running a battery down can really ruin it. More likely to cause harm than an overvoltage which will boil the liquid.

[air-cooled or diesel]

he says his idiot light works fine; but in all mine im sure its a small red wire; may be with black like you have, that goes to idiot light. the red wire, looks like its going to some ground; the other terminal i do believe is the w, which is tach, or upshift(tach reading). i dont see how a red wire looks like its going to a ground??
you also say low ohm reading while testing ground, a high reading is bad, a low reading is better. if you know how to do a voltage drop test, for ground too.
you need to clean up corrosion, spray clean w/electronic cleaner. new washers i like, new fasteners too. like i said i ran a ground from trans tunnel main ground to alt top, and from alt top to fuel filter mount (cleaning all contacts), i then used something like wd40 to help some with electrical contact & some with corrosion. for alt mounting of grounds i got a longer allen bolt for top alt mount with multiple washers and a nut. anti-seize. got ground wires from napa, the one maybe their longest

[StevenPH]

I suppose I can wait and troubleshoot which is which when I install the new battery (warranty exchange) and starter later tonight. Right now I don't even have enough power in the battery to see if the idiot light comes on.

My hope is it's the starter alone causing my trouble. The blue wire splice looks fine, and the starter connections were definitely non functioning. Unless that problem can then effect other things I'm hoping I'm good.

I was planning on installing an oil pressure gauge I'm the dash as well, so I'll add a voltage reader to that too.

[82vdub]

I was planning on installing an oil pressure gauge I'm the dash as well, so I'll add a voltage reader to that too.

Remember that you have to "T" a fitting in there so that the stock oil pressure system will still function and that buzzer doesn't go off above or below 2000 RPM.

[StevenPH]

Thanks - I don't even yet know the first thing about putting in an oil pressure gauge, I'm sure I'll be back to bother you all for help when I get there

Thanks again for the help, I'll let you know what I find with the new starter and battery.

[82vdub]

Thanks - I don't even yet know the first thing about putting in an oil pressure gauge, I'm sure I'll be back to bother you all for help when I get there

It's not the gauge install that'll be an issue. If you try to replace one sender unti with the fitting for your gauge, the oil light and buzzer will either be on when the engine is above or below 2000 RPM and it will drive you nuts. You'll either have to put a "T" fitting in and keep the original setup, or disable the oil control system.

[air-cooled or diesel]

i prefer a 't' with a base, if you can find one, so you can use a copper washer and then use permatex if you need to, i dont put any sealer/tape on threads.
better to keep warning light on dash active too,

[TylerDurden]

The blue wire is the exciter wire... it goes through the LED in the cluster.

When the engine is off, current flows to ground through the LED and alternator. When the engine runs, the alternator field is energized by the blue wire until it is generating >12V, then no current can flow to ground through the LED and it goes out.

If the LED ever fails to light, it is very likely the blue wire has fatigued from vibration inside the insulation near the alternator and is intermittent. Poor connection = no charge.

A way to test charging and blue wire:
Disconnect blue wire from alt and ground blue wire... with key on, LED should be lit. Wiggle blue wire to check for intermit.
With engine running, jumper directly from +12V to terminal where the blue wire connects. The alternator should then output >13.5.
Never run engine/alternator without battery.

[air-cooled or diesel]

look at pic, the red wire w/black stripe looks as if its grounded to alt body connection

[air-cooled or diesel]

the interesting thing, some of these wires can work more consistent if done like this: 2 wires of 1/2 the size of 1 wire, such as bigger wires, like the charging wire(2batt;or starter boss+), or big grounding wires. 2 wires each 1/2 the size/rating of bigger wires, 2 separate connectors for each wire, hook up to same terminal(both,2).

[bc]

Did you get the bolts back in? Usually I can just jack the engine up a little bit until those holes line up. I made the mistake of removing the bolts on my first starter swap and the engine just drops like 4 inches. Freaked me out. Good luck!