MIDNFauciUSN

iTrader: (8)

This will be my last thread for a bit - at least on this topic.

The 'vert is dying... every few weeks. It left me stranded on the side of I95 in St Augustine, FL. The battery was just dead. This made me think one of a few things:

1. My battery relocation job sucked
2. My alternator is toast (wont charge)
3. My alternator has wiring issues (causing it to not charge)
4. My battery is toast (wont hold a charge)

Upon recharging the battery, it tested good. Upon bench testing the alternator, it tested good. A few weeks later (today), the battery was dead again. I took the battery to have it charged again... and once again, it tested good.

Tomorrow I'll be taking the alternator to an actual alt rebuild shop, to see if they can find anything wrong with it.

I mentioned that I relocated the battery; I moved it all the way to the trunk. I used about 14 feet of 2 gauge Hobart copper welding cable to a post in the engine bay where the car's electrical load ties in. The first time I had the battery charged, I ran an 8 gauge cable from the alternator post to this post.

Do the 2 wires on the alternator harness (s5) have an effect on the ability of the alternator to charge the battery? Looking in the wiring diagram, one of the two (W/L I think) should be providing the alt with 12 volts. If it isn't providing the voltage, will that keep the alternator from charging?

I hooked up an ammeter between the battery cables and battery, with the car off, and surprisingly, there was a very brief small spark. The load went from .5A to less than .1, with nothing registering on the <200mA scale.

demon721

iTrader: (14)

did u see if it is charging when its on the car. get the car running and put a multi meter on it and see if its charging on the car while its running

AGreen

iTrader: (11)

Need me to come down and take a look at it?

I usually hook up a test light between the battery and negative cable to find parasitic draws. If it lights the bulb, there's a draw. Otherwise, don't waste your time.

I don't remember completely how the S5 alternator is connected, give me a minute to look at the drawing. One wire, at least, is for the exciter. If it's not making good connection in there, the alternator's output could be pretty weak. Does your dash voltmeter work?

satch

iTrader: (1)

You have an S4 w/an S4 alternator or an S4 w/an S5 alternator?

AGreen

iTrader: (11)

S4 car
S5 alternator
Megasquirt ECU (makes things kind of irrelevant)

I was right. One wire is for the exciter, one is for the dash meter.

satch

iTrader: (1)

If you have an S5 alternator then the non W/B wire must run to the engine fuse box for constant voltage or the alternator will drain the battery over a short period of time. And the W/B wire must have very low voltage (1 to 3 volts) w/key to on and this will cause the idiot lights to come on. This low voltage on the W/B wire excites the alternator so when it starts turning the alternator puts out voltage.

MIDNFauciUSN

iTrader: (8)

Hmmm. A test light is about the only tool that I ever refused to buy.

This is an S4 Vert, with S5 Engine, and S5 Alt. Unsure of the harness - on the body side anyway (alt, fuses, brake stuff, anything other that what I wired when I did the MS - whatever that harness is called), but Satch, I think that post gives me a solid starting point.

AGreen, come on down on Saturday. I owe you a beer anyway. Afternoon though, I have duty that day.

I'll start digging tomorrow

satch

iTrader: (1)

Once the car starts up though, the voltage on the W/B will return to 12 volts unless the alternator is malfunctioning and then the voltage drops to a low level.

And to repeat, the B/W wire goes to constant voltage on an S5 while on an S4 the B/W wire goes to switched power. If this change is not made the battery will be drawn down.

AGreen

iTrader: (11)

I think I'm working all that day. Turns out, "we're" having battery problems too

j9fd3s

iTrader: (3)

either this, or on my T2 there was a splice/staple in the charging system harness that was bad, so the alternator was new, battery was new, but the voltage with the car running was low.

the fix was accidental, but i did a 20B swap, and then when i went back to the 13BT, i had the same battery, same alternator, but a different charging system harness, and the problem was gone.

MIDNFauciUSN

iTrader: (8)

Newest test results...

Battery: Normal (12.42V with 637CCA

Starter: Normal (11.73V/36.6A)

Alternator: HIGH VOLTAGE
No Load Loaded
------------------------------
15.05V | 14.9V
15.0A | 10.2A

Ripple - 31mV

WTF is a "ripple?" A measurement of how well the rectifier is working? Looks pretty solid.

The engine was run at about 2500 RPM during the alt testing.

MIDNFauciUSN

iTrader: (8)

oh yeah, and I don't have idiot lights, so what happens with the W/B wire then?

satch

iTrader: (1)

If you don't have the idiot light unit you could measure the W/B wire at the CPU. It's found in the largest CPU plug and would measure 1 to 3 volts w/key to on 12 volts at other times. And is your B/W wire at the alternator wired to constant voltage and not switched power, which is how it was originally wired. If you unplugged this wire from the alternator it would have constant voltage if it were wired correctly and if it only had voltage w/key to on then it is wired incorrectly. And the ground for the charging system needs to be solid.

MIDNFauciUSN

iTrader: (8)

So just hit the car with the volt meter... both wires have no voltage - car on or off... I have some work to do.

Looking at the wiring diagram... W/L goes to 12V constant - that is easy enough to make happen. Or should I figure out why it isn't happening first?

MIDNFauciUSN

iTrader: (8)

update. Just happened to see a random W/L wire hanging uncrimped in the engine bay. Continuity test says that its the same W/L from the alt.

So theres about half of problem number 1.

AGreen

iTrader: (11)

So something pinched your wires?

satch

iTrader: (1)

I think you mean White/Black (W/B).

MIDNFauciUSN

iTrader: (8)

at the VERY least, W/L is cut.

still have to figure out what to do with W/B... Satch, I believe you, I'm just figuring it all out in the wiring diagrams. Don't see anything about the CPU interfacing with the alternator. Looks like the W/B wire is an output from the idiot light directly to the alt.

I'm not saying (at all) that it wouldn't work... just that I'm not at that point yet, but I'm sure I will be soon.

MIDNFauciUSN

iTrader: (8)

no, white/blue.

Two wires going to the alt are white blue, white black. however... I have an intermediate harness that's about a foot long that goes from the alternator terminals to the rest of the main harness.

THAT harness has a white/something and a yellow/something wire.

satch

iTrader: (1)

I forgot you had an S5 engine in your S4 so the W/L is as it should be. So the two wire plug would be a W/L and a W/B wire so forget some of things I mentioned earlier about the B/W wire for on your car the B/W wire is your output wire, the W/L wire would be constant voltage powered by the engine fuse box and the W/B wire would have 1 to 3 volts w/key to on but engine off (and plug connected to alternator) while having 12 volts w/engine running.

MIDNFauciUSN

iTrader: (8)

And you're saying I can give the alternator 1-3V by tapping a wire at the CPU?

satch

iTrader: (1)

What causes the voltage to drop to 1 to 3 volts is coming from the alternator itself so it is internal to the alternator as opposed to external.

The CPU houses the Alternator Warning Light Relay. It is powered by the Meter fuse. There should be a slot in this CPU plug (largest plug -W/B wire). I believe the voltage from the Meter fuse backfeeds through the relay so if the plug were removed from the back of the alternator w/key to on the wire would then have 12 vols.

MIDNFauciUSN

iTrader: (8)

So does that wire even need to be connected to anything if I have no idiot light? It sounds like its just an output to the idiot light to tell you if your alternator sucks... though it has to be more complicated.

EDIT: just saw YOUR edit... makes a little more sense now

Will report back tomorrow!

satch

iTrader: (1)

Not 100% sure the voltage backfeeds through the relay but I seem to remember Hailers stating such. It would be rather easy for you to check by probing that slot in the CPU w/key to on, engine off and see if you get 12 volts or not. If that particular plug had the wire depinned then that slot would be located next to the Green/White wire and above the Blue wire.

MIDNFauciUSN

iTrader: (8)

It looks like the idiot cluster actually contains the alt warning light relay (this would mean I'm SOL)... C-3 of the wiring diagram.

You're right about it being fed by the "meter" fuse, I just don't know about it being backfed because of the circuitry in the alternator.