waltersaegir

keyRap!

I'm 99% certain that it is the L-wire and not the S-wire that was connected on the alternator plug.

I descided the Alternator must be bad and took it to the Alt Rebuild shop. They verified and rebuilt it - generally said even though it looked new, the stator +++ were all bad.

Now, after reinstalling the alternator and reconnecting the battery positive, I get no response when I turn the key On. Beaper notices that key is in and door is open, lights work, dash lights work, but no idiot lights and no starter.

Did a quick fuse check and found nothing. Must be missing something.

HAILERS

On a series four car, the L wire leaves the alternator plug and enters the CPU as a white/black wire.

IN the CPU it goes to the alternator Relays coil and acts as the negative side of that coil. The relay then pulls in and feeds a ground to the warning light assy. That gnd turns on all the Warning Lights IF the warning light assy has good soder joints.

There's a couple of things you can do.

One is to turn the key to ON, engine OFF and probe the white/black wire at the alternator plug WITH the plug on the alternator. The meter should read 1-3vdc (it's stated so in the ENGINE ELECTRICAL section of the FSM).

Another thing one could do, is go to the CPU and find the wire that is Yellow/Blue. You can do this with the CPU plug off the CPU. Now, with the key to ON, engine OFF, put a ground on the Yellow/Blue wire. The warning lights should come on when you do that act.

If the warning lights don't come on, then the warning light assy has bad solder joints or a bulb out (ain't likely). Sometimes if you pull the warning light assy out a bit from it's installed position, and leave its plug on, you can bend/manipulate that plug while looking to see if the lights come on (yellow/blue has to grounded to do this). Sometimes you'll see all the lights come on momentarily verifying the warning light assy needs it's solder joints resoldered.

Or you can ohm out the white/black wire from the alternator to the CPU plug where it enters that CPU plug. Meter with long leads needed to do that.

Lots of different things you could do.

Pay attention where I say *key ON, engine OFF*.

As you can see from the jpg attached, on a series four the L does not get fed from the warning light assy itself, but from the coil in the alternator relay. That's why I'd first put the key to ON, engine OFF, and probe the L wire while the plug is on the alternator (wrong results if you pull the plug off and do this). You should see 1-3vdc IF the L wire is leaving the alternator and going to the negative side of the alt relays coil.

I just did this after writing the above, on two cars. Both series four with series five alternators. Ones L wire read .78vdc and the other cars read 2.8vdc. I'm not sure what to think about the .78vdc but alls well with both cars.

waltersaegir

Hailers, your description is pretty detailed. However, I'm not sure my car still qualifies as a series four car, since it now has a turbo'd 13BRE from a Cosmo and a Haltech E8 Computer.

B4 I had the alternator rebuilt, the car had been running for 6-7 months. Then it stopped charging. Then I noticed the alternator plug had 1 wire connected and 1 loose. Then I became 99% sure that the connected wire was the L-wire (not the S). Connecting what *looked* like the S-wire didn't help, so I headed for the rebuild shop. (BTW: the L-wire(i think) is connected to a relay that's bolted next to the main fuse box)

Now with the rebuilt alternator installed and battery positive reconnected, the ignition key is ignored by the starter. Also, the relay where the alternator plug wire is connected, no longer provides the previous 12 volts.

AND *all* the idiot lights are OFF.

HAILERS

Well, the ECU never had anything to do with the alternator on the original car anyway. The CPU next to your left foot did, in that it had a *altenator relay* (see diagram in my last post). And the COIL on that relay in the CPU is what fed the L wire.

The relay you describe does not sound like the original relay, since it was internal to the CPU on the original car and the L was fed from the coil on the relay, not its contacts.

On a series four the warning light assy does nothing more than alert the driver if the alternator works or not. Unlike a series five where the actual voltage comes from the warning light assy thru the bulbs.

I wonder if you still have a CPU?????? Near the left foot? First item aft of the interior fuse box?

I don't know what else to say. But something tells me running batt voltage straight off a fuse isn't the way to go. It's like I'm trying to say if you picked volgage right off a fuse and put it to ground......you'd pop the fuse. Right? Right. But when you run a wire to the COIL of a relay, and put the other side of that coil to ground, it pops no fuse and just pulls and hold in the relay. Same with the light bulbs in a series five. You put power from a fuse to one side of the bulb and the ground the other side of the bulbs filiment and all that happens is the bulb lights up.

I'm not going out to my car and apply batt voltage straight off a fuse just to see what happens. Although I have to admit I've crossed up the L and S wires in the past for short periods of time til I realized I had fudged up.

Long way to say I've no answer for you.

HAILERS

Do something like SIM RX3 posted on this thread earlier. See how he uses a relays COIL for the power for the L wire. NOT the contacts on a relay, but the negative side of a coil. Just power a coil from a fuse that only has power when the ignition is ON. The run the negative side of the that COIL to the the L terminal on your alternator. You don't care whether the contacts of that relay have any wires going to them or not. It matters not. It's the power passing thru the COIL of the relay that supplys the power.

This will do nothing for the warning lights coming on, but will supply power to the L wire. If you want the waring lights to work also, then just put one contact on that relay to ground and the other to the yellow/blue wire that runs to the warning light assy from the CPU plug.

EDIT: I forgot you'd need that diode in his picture. Might not though.

But when you get right down to it, his picture apes the series four method and you already have that in place IF the CPU is still there (left foot area).

EDIT: Hell this is bugging me. Pull the L wire off the alternator. Should be WHITE/black. Key ON. See if that wire has 12vdc(batt volage) on it or not. IF it has batt voltage, then I'd say it's still tied to the relay coil in the CPU. And if so, then when you put that wire back on the alternator itself, then the voltage would drop to 1-3vdc...because its now passing thru the rotors field coil and going to ground.

EDIT AGAIN: I attached a jpg of the fuse that powers the alt relay in the CPU. So, it you pull the L wire off the alternator, and it reads batt voltage with the key ON, then go pull that fuse and measure the L wire again. The voltage should have disappeard more or less proving the alt relay is supplying power to the L wire.

You don't wanna run power to the L wire straight off a fuse or relay contact tied directly to a fuse.

waltersaegir

There is 0 volts on the L-wire, but remember that it *looks* to me that the alternator was installed with *only* the L-wire connected and the S-wire loose.

The L-wire is connected to a 30 AMP relay that is mounted adjacent to the engine bay fuse box by the battery. It is connect to terminal 85.

Terminal 85 did have 12 volts at some point before I descided the alternator was bad.
Maybe the relay went bad. I'll go to Radio Shack and get a new one first thin in the morning.
Then maybe the engine will start and I can address my clear suspicion that it is the L-wire that is connected and the S-wire loose. Which is likely the root of the original problem.
BTW:thanks for hanging-in-there with me; your knowledge is very helpful to me.

HAILERS

Remember what I said. Do Not attach the L wire to a direct source of batt power. IN the stock configuration it is connected to the Negative side of the alternator relays coil, in the CPU. That wire is not directly connected to a batt source. Well, depends how you look at it. It is connected to a relays coil of??????? I don't know how many ohms. I guess sixty to eighty ohms.

I also forget what 85 is on a radio shack relay. I'll take a look ......sometime.

EDIT: JPG attached. You could maybe just use a sixty eight ohm resistor instead of a relay. Never done that myself. I'd have used the stock relay in the CPU.

HAILERS

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newkid2rotary2012

iTrader: (3)

bringing this thread back from the dead....i have a s5 and just replaced the alternator yesterday with a fd one. It only charges on and off sometimes. Like this morning when i left for work it was charging (from what the gauge said) and then it dropped under 12 volts before i got to work. Came home to put a volt meter on it and the alternator is reading the same as the battery. i cant imagine this alternator being bad right out the box huh?

satch

iTrader: (1)

You wired it up exactly like the S5 alternator which involves 3 wires? White/Black wire to the back of the unit, the output wire, plus the wire running to constant voltage? If so, then it could easily be the alternator, albeit new.

misterstyx69

iTrader: (142)

I totally agree.
I bought a Brand spanking NEW/Re manned..whatever.. off a guy here.(mind you 4 years ago).
It gave me nothing but problems.

I buy a used 50 buck FD alt and it is still going.