Alternator AC Wire

[ramilolah]

Gentlemen .. The alternator has an AC wire as illustrated in the image attached .. Also as showing in the alternator (generator) wiring harness there is a plug wire (apart from the ground and the battery+ wires) that I do not where it should go? .. Should the AC wire from the alternator be plugged into the wire showing in the alternator wiring harness or what? Thank you guys!

[gunny flip]

The number on my wire says 568, I'll post a picture later on
mark

[svramselaar]

hi

this wire come`s from the contact
it is there for tad the alternator start up
normality at a presto lite it is a little wire hanging out
you can try it let the alternator running on a stand
take a testing light one side 24v the other at the bold (if you make a short only the light will light up nothing will burn out )
if it go charge you can put it there

george

[gunny flip]

here is a picture of the 151 wires going to the alternator
mark

[gunny flip]

the picture didn't downsize,photobucket don't work and it's harder to do
mark

[ramilolah]

Dear Geroge and Mark .. The image attached is an excerpt from the front wiring harness of the M718A1. Would you please tell me what is the use of that little female plug highlighted by the Red rectangle in the image? Also, if it should be connected then to where it should go? I thank you a lot for your help!

[Rickf]

That picture is a little confusing since the wires are not individually numbered or shown in the correct scale to size. I see four wires coming out of the harness there. Is that part of a M151 diagram? If so what manual so I can get a better look at it. Aren't you going with a Mercedes alternator? All internally regulated alternators will have either 1, 2 or 3 wires. One wire alternators are a US thing only I believe. 2 wire will be a charging wire to the battery which will be a larger wire and a field wire from a switched ignition source. 3 wire will usually be the two wires mentioned before plus a larger ground wire from the alternator to the engine block or body.

Rick

[gunny flip]

For the picture I posted, I can look at the wire numbers and say what they are,if it would help
mark

[Rickf]

Mark, Yours are field, charge and ground, top to bottom. His pic has an extra wire and he mentioned before that he was going with a Mercedes or some other truck alternator. I just need to verify what that diagram is from.

Rick

[svramselaar]

hi

again the little wire is connected at the wire you can see above the + wire in the picture
in the picture you can see it coming from the silicone putty
it is there to start the alternator up with power from the contact

george

[Rickf]

That would be the field wire. It would have switched power on it. When the key is on there is power and when the key is off there is none. The amount of voltage on that wire determines the output of the alternator.

Rick

[ramilolah]

Dear Rick and others .. The wiring is now connected to the alternator battery + terminal and the other wire goes to the ground terminal. The car is running perfectly, the batteries are charging and the gauge is now showing the correct power indication at the very top end of the green range. What is worrying me is that remaining little plug wire which looks like is loosing. So, Rick to which terminal on the Mercedes alternator this little wire (field wire) should be connected to? Thanks

[svramselaar]

hello

you are confusing us all
at the Mercedes alternator you do NOT need the wire
it has the begin from the control light ( contact - light - D+/61)
a Presto-lite has no control light and use the little + wire from the contact to start up

a Bosch is inside different build it has 3 diode`s for the field power

maybe this helps this is the Bosch system
http://www.vtr.org/maintain/alternator-overview.shtml

george

[Rickf]

OK, I am going to give up at this point because I do not know what wiring is being used on what alternator. IF it is a Bosch alternator then the diagram George has provided should answer your questions.

Rick

[Kurt Lesser]

That wire is used in the HMMWV to tell the protective control box that the vehicle is running. Since there's no coil or tachometer output in a diesel it needs some other way to know the engine is running.

Kurt