Read in the FAQ (I think it was) that the charge voltage should be from 13.50 to 15.00 volts and no greater. I did a s5 swap into my s4 and ran the S to a full time positive due to the difference in how the alternators operate electronically. Didn't bother with the L at the moment (for the idiot lights I do believe). I fired the car up to my ~750 rpm idle and the gauge reads 14 volts on the spot. Yes i have a stock pulley. I was pleased but double checked at the alternator which I discovered said 15.00 volts not .01 over or under. Checked at the battery and it was the exact same reading.

Well, should I be nervous about charging at EXACTLY the limit? it doesn't give me much headroom.. Although It is within the allowance of charge voltage... but why so high? could it be my regulator is on its way out? are there any negative side effects of charging so well? I noticed when revving the engine the volts actually dropped by about .05 (14.95). once the rpms came back down and idled then it held a steady 15.00v again.

 

When in doubt, connect the alternator like the factory did.

See the second jpg. Try that out on your car. Use a sewing needle to ***** the wire going to L or backprobe the wire. The plug HAS to be connected up to the alternator when you do this and the white/black wire has to be installed.

I'm pretty sure this 1-3 voltage is initial excitation voltage for the field coming from the warning light circuit. The voltage is coming from the white black wire not the alternator. But then again I've seen what your seeing in that with just the S wire on the alternator will put out with no L wire connected.

Make sure your not confusing the S and the L terminals on the alternator.

You still have the WHITE/BLACK wire from the series four on the stock harness. So get a small piece of wire and crimp on a male connector on one end and a female on the other end. The use that wire to jumper the White/Black wire to the L terminal.

THEN go look at the large output terminal on the alternator. I think you'll find it's not 15vdc anymore but in the mid 14's. Please write back as to what happens when you do that. It cannot hurt to do that but might help.

And when your not doing anything and have spare time, do the Voltage drop tests in the last jpg I attached. Or go here and look halfway down the page for Volgage Drop Test: http://www.aa1car.com/library/charging_checks.htm

 

Hailers has given you the answer you need. S to the fuse block and L to the charge light. Just use the original harness wires.

Here is some advice for General Purpose Use: Put things back like you found them, or in this case put them back where they belong. This axiom will prevent many troubles.

Look at your post. You didn't bother to hook up some of the wires, then you wonder why the alt doesn't work right? The logic of that alone should answer your question. Not pounding on you, just trying to help by showing you that you had the answer to your question in the question itself.

Good Luck and enjoy your new voltage prowess!

 

I have about five alternators in the back shed. Some are known good series four turbo and the others are either bought off this forum or E-bay and are series five.

Well, one is a rebuild that looks brand new on the inside and the outside that I bought in the last couple of years. It didn't work right. The voltage jumps around rapidly from 13-15 volts. In other words acted flat odd. So I put a spare on that car and put this one in the shed.

So I've been getting into alternators and how they work. So I took it apart. I've taken 'em apart and installed new brushes/regulators in the past, so it was fairly straight fwd. Well when I pulled it apart I noticed a little black piece of carbon that fell out. It had a smooth, curved side that looked just like the area that the carbon brushes ride on the slip rings. So, ah ha! But then I looked at the brushes and they looked brand new. There's no way that piece of carbon could have been part of those two brand new looking brushes.

So, I almost couldn't make up my mind what to do with that alternator. I checked out the diode assy per FSM and slip rings etc and they were good. So I got into my *what if* mode and re assy it and put it back on the engine a little while ago. It works like a charm. I've no idea where that piece of carbon came from. I suspect it came out of the alternator before it got rebuilt the last time........but everything inside and outside looks soooo clean and new. It'll always be a mystery as to where it came from. I suspect it was shorting things inside momentarily on and off. I never heard any strange noises though. Just a rapidly changing output voltage.

Jpg attached of another alt inside that shows how new brushes look and a picture of the piece of carbon mentioned above.

That said, I've questioned whether the L has to be connected or not recently. The regulator is INSIDE the alternator and the L wire always seems to be a warning light function wire but probably supplys a initial excitation voltage for the field. After excitation it seems to me to play no function other than to keep the warning light off.

First jpg is the piece of carbon next to a quarter.

Second jpg is of what good carbon brushes look like. The small hole is made for a piece of wire to pass thru to hold the brushes full down so the bearings can pass over them.

Last jpg is just a jpg of the back of the alternator to show how clean and new it looked.

Last jpg is of yet another alternator that didn't work right. I notice it has not as many windings. The red arrow points to where a normal series five would have a winding wire. Compare that view with the jpg next to last. I'm gonna chunk that one. Darn if I'll buy a fifty buck regulator for an oddball alt that probably won't put out.

 

Here's another jpg. The brushes are flat worn out. Compare the length of those brushes with the brushes in the other jpgs. I might just spend fifty bucks for another regulator and brush set for that alt.

 

Before I get jumped about my wonderment about why one alt has but three windings whereas the other alternators have four windings........the attached jpgs explain it. My bad.

And if I could figure out which kind of regulator I have, I could figure out if the L wire HAS to be connected or.....not. Last two jpgs.

 

Thanks for the replies. This afternoon I went out to my car and attached the w/b tire to the -what i thought- was the L terminal like instructed with the other terminal to the constant power source, then started it up. It still read 15 volts. After some problem solving I came to the conclusion that apparently I had the terminals flip flopped. I don't know if it's because didn't have the factory plug for the alternator or what it was. but I flip flopped the 2 'tires on the alternator. Then fired him up and held 14 volts. I am grateful that the car was charging properly.

I then decided to shut the car off and unplug the L terminal then restarted it and it would not charge at all. so apparently you do need the L terminal to the idiot lights hooked up for the alternator to function at all. with my s4 alternator this didn't seem to be the case. which was the cause of some confusion for me..

But now i have a properly functioning alternator and that's very gratifying.

the only problem that remains is that my alternator is from a s5 na and has the terminal on the top of the alternator.. perfect for water to pool up in (because i don't have the correct water proof connector.) i don't know what i can do to prevent water from pooling up in it. ideas?

 

nice one..


load sensative alternators (s5 and s6) need the charge light connection to keep it happy.

get a plug from the wreckers.. most modern cars run that plug

as water sitting in the terminals will lead to corrosion which will work its way into the alt and cause problems as we have found..