Bubba Alternator wiring

[gedmeyer]

Looking at my alternator last night, I realized that bubba worked on it before I owned it. The brown wire to the 2-prong connector is fine, but the red wire to the connector is connected directly to the red post on the back of the alternator. A yellow battery wire is also connected to the post on the back of the alternator. I also noticed that there is a cut red wire coming from the T-fitting on the wiriing harness running along the drivers side fender of the car.

Am I correct that the cut red wire is supposed to be connected to the pronged connector of the alternator instead of the second prong being connected directly to the alternator post? The cut wire shows +12V right now, so it is still connected to the battery. I feel like the current wiring setup is fooling the alternator because it's reading the output directly from itself?

-gedmeyer

 

[mkapp7879]

The underhood light is factory spliced into that red wire at the fender, could that be what was cut off? There are 2 red wires that go to the alternater, one to a 2 wire plug in and one to the stud. Could that yellow wire have been added to supply power to something aftermarket? Add on alarm or something?

Mike

 

[Bob Chadwick]

It appears that the prior owner added a larger charge wire, which would suggest that you might have a higher amp alternator. He may have just liked the color and decided to go with it.

I don't have the wiring diagram in front of me but if I recall correctly, in addition to the hot charge wire, one of the wires coming off the plug is hot as well. The loop together somewhere in the wiring harness and are used to generate the signal for the charge light.

It appears that the wire broke of the plug and he simply found another source of power off the alternator. It would appear to work this way but someone more knowledgable of how that system works will have to clarify.

I have a printout for this circuit on my 77 at home. Probably the same. Let me know if you would like me to post a copy.

 

[gedmeyer]

The underhood light works correctly, it is an stock replacement alternator and there is no aftermarket electrical equipment in the car.

I have the shop manual and assembly manual at home, so I'll have to give a look.

 

[gedmeyer]

Here are two pics of my alternator wiring (please excuse the wire nut/ electrical tape, they are temporary until I figure out the correct way to wire this sucker.) The two yellow butt-splice connectors are both red wires and carry the battery voltage. Should the two prong connector be connected to one of these and the other run to the post on the back of the alternator? There is a heavy gage yellow wire that runs from the post of the alternator to the battery, along the frame of the car (inside a thick rubber tube).

thanks, gedmeyer (sorry about the big pics)

 

[mkapp7879]

Here are two pics of my alternator wiring (please excuse the wire nut/ electrical tape, they are temporary until I figure out the correct way to wire this sucker.) The two yellow butt-splice connectors are both red wires and carry the battery voltage. Should the two prong connector be connected to one of these and the other run to the post on the back of the alternator? There is a heavy gage yellow wire that runs from the post of the alternator to the battery, along the frame of the car (inside a thick rubber tube).

Pretty sure what you think needs to be done is correct. I'm thinking one of the 2 fused links at the starter may have burned out so someone ran the yellow to the battery. Not sure on the 81 but on my 78/79s there are no wires going to the battery, all hot leads come off the starter terminal. Check the fused links at the starter. You say both the red leads at the fender by the alternater are hot?

Mike

 

[goertz]

the first thing i notice is that it is an aftermarket "Help" pep-boys style plug at the alternator. that brown wire is spliced into the white wire because that is where the brown wire went in the original plug. although the red wire should not just go back into the alternator. I noticed in the picture there is a green wire hanging out down there, what does that go to? my guess is that green wire should to to the other terminal of the plug. Someone might know better, but i'm pretty sure the plug wires originally were the green and for sure the brown. That green wire probably is a 12v source off the ignition switch to power up the alternator. they way it is now with the wire jumping right over to the battery lead, means the alternator is always "on" even if the ingnition switch is off. no big deal, just could drain your battery if not started for a long time, and probably not really good for the alternator.

 

[goertz]

actually, i take that back, i think if that red wire that comes out of the harness is switched, it goes into the plug. if I were you, i'd go to a junk yard, and get an original GM plug (any car will work, they're all the same) and cut a good section of the harness with it. then splice into your harness in an unnoticeable place, and it would then look stock.

 

[mike weyman]

the brown goes to the white, the red wire that is with the brown wire goes to the other half of the plug,

 

[mkapp7879]

The green wire mentioned above just goes to the temp. sending unit.

 

[Bob Chadwick]

The wiring schematic for the alternator on a late 77 as well as an explanation on how the system works. Two parts because of the size. http://home.comcast.net/~bearden525/Alternator1.jpg
http://home.comcast.net/~bearden525/Alternator2.jpg

One of the two 10 gauge wires is on the plug, the other is on the post. They come together at the point where the red wire goes to the under hood light. The combined wire continues to the fusible link at the solenoid ( not shown). The brown wire comes off the plug and connects to the generator light through the circuit board.

Yours might be a little different. Hope this helps.

 

[gedmeyer]

I went ahead and put the red wire from the 2pronged thingy to the red wire in the harness. (Yes, it is a HELP replacement plug). I'm getting better charge with the car running now (14V). So I guess someone got cute and just ran another battery cable directly to the alternator.

The one thing I noticed when I started the car back up after about 2hrs of sitting was the volts were down around 12 and the battery light was on for about 30 seconds after start. This makes me wonder if I'm getting some battery drain with it sitting. I'll have to wait until the weekend when I have time to charge the battery at home if it dies out. In the mean time, I'll just use the quick connect at the battery for insurance.

...one step at a time.

-gedmeyer

 

[goertz]

it's very possible that with the alternator powered "on" all the time like it was, that you might have damaged the regulator. start the car, and don't rev it, just let it idle, check your volt gage and see if it's low. then whap the throttle up over 3500, and see if the gage pops up to 14 and stays there. if so, you have a bad alternator. alternators need 12v power to be "turned on", which is why there is a wire that runs off the ignition switch. but....the alternator will generate enough power to turn itself on above 2500-3500 rpm with out it, and charge fine. not sure if this is a diode or regulator isssue, but i've had it a few times on a few vehicles. luckily the alternators are cheap, or if #'s matching is important, you can have yours rebuilt.

 

[bossvette]

Looping the red wire to the A+ terminal is an old Hot Rodders trick you then can run a heavy gage wire to the battery simular to a "1 wire" alternator in a stock system the two come together at some point anyway so why waste wire.

the small wire is the accessory feed which "excites" the alternator so it charges the system