Alternator ground question (1 Viewer)

[jvincig01]

OK, let me start this thread by saying electrical is not my strong suit. Now thats out of the way, I am trying to figure out why my alternator isn't charging my battery. I replaced the alternator and no luck. Here is were my ridiculous question comes into play........

Right now my alternator is grounded to the block. Would it make the slightest difference if its grounded the the chassis? I have a "universal" GM harness so I am running a one-wire alternator.

 

[reddingcruiser]

Have you checked the voltage output at the alternator?

 

[jvincig01]

Have you checked the voltage output at the alternator?

Just tested. Here are some numbers.

Off - 11.38v
Running - 11.14v
Running w/ lights - 11.01v

I just installed the new alternator yesterday and am basically having the same sort of thing going on.

 

[4x4veteran]

I take it the red wire loops from the batt post to the plug in the alt.
Hook a 12V incandescent bulb to the white wire and to a wire that is hot with ignition is in run position.
The light should come on when the switch is in run mode.
should go out when engine is running.
The white wire excites the field on start up.
With out the white wire hook up the alt. has to do 15-2000 rpm before it starts charging.

 

[bikersmurf]

I think he’s getting at the fact that you don’t really have a 1 wire alternator. If it’s wired in in the original manner (rather than “1 Wire”) it’ll perform better.

To answer a previous question, keep the alternator grounded to the block and make sure there is a good ground strap from the block and the frame.

 

[jvincig01]

I think he’s getting at the fact that you don’t really have a 1 wire alternator. If it’s wired in in the original manner (rather than “1 Wire”) it’ll perform better.

To answer a previous question, keep the alternator grounded to the block and make sure there is a good ground strap from the block and the frame.

Thanks. the picture is misleading because the red wire should be on the other side. If the white wire is supposed to go to an "idiot light", and i dont have it hooked up, is that an issue?

 

[4x4veteran]

This is the simplest diagram I could find.
From what I can make out on your photo the exciter hooked directly to the batt is going to let electricity bleed back through the field and discharge the batt even with the key off.

 

[shelfboy1]

i could be wrong but i have several gm alternators like that where there is a factory jumper between the light wire and key wire .when i use them i jump the 2 together and im good .i think the jumper may be the early 1 wire alt set up

 

[Steamer]

Here's another pic to confirm what 4x4veteran said. You have a three wire alternator. I'd consider using the indicator light since you have the terminal for it. You can get a connector with the diode built in that would plug in between your alt and connector. "Diode Connector"

 

[jvincig01]

This is the simplest diagram I could find.
From what I can make out on your photo the exciter hooked directly to the batt is going to let electricity bleed back through the field and discharge the batt even with the key off.
View attachment 1781667

Looking at your image (thanks by the way), I have the red wired up the way it should be. The Green wire is removed. Should I add that back in? I dont have a dash light but I could improvise. Would that solve it?

 

[jvincig01]

Here's another pic to confirm what 4x4veteran said. You have a three wire alternator. I'd consider using the indicator light since you have the terminal for it. You can get a connector with the diode built in that would plug in between your alt and connector. "Diode Connector"

View attachment 1781714

Thanks for the image and link to the diode!! Amateur question here regarding the ebay harness. Would one side simply plug into the alternator? Looks to me like the green is the charging side and the brown is the diode side. I would just continue the diode side to the load side of the ignition?

 

[Steamer]

Rather than color, go by terminal numbers. They are embossed into the body of the Alt. I believe I can see them in your pic.
Terminal #1 is for the indicator light if you choose to use it. Cap it off if you don't. If you do, terminal #1 would go through a diode, then through a indicator lamp, and then to a 12v source switched by the ignition switch.

Terminal #2 is for sensing. It's the one that you should jump to the big lug. The reason they didn't do it internally (like on a one wire alt) is so you have the option to sense your voltage further away such as when you have a large draw item far from the battery. Like a big amp or refrigerator in the rear of your vehicle.

In short, just swap those two small wires on terminals #1 and #2.

 

[Steamer]

Here's a pic of mine.

 

[4x4veteran]

Looking at your image (thanks by the way), I have the red wired up the way it should be. The Green wire is removed. Should I add that back in? I dont have a dash light but I could improvise. Would that solve it?

The wire that loops back to the battery terminal on the alternator should go in Number two (2) spot as Steamer pointed out.
You can run with out the diode wire on number one (1) but will have to rev the engine up to about 2,000 rpms to get the alt to start charging.
It might kick out at idle.

 

[jvincig01]

@Steamer @4x4veteran thanks guys. Here is how I had it wired up. I bumped up the RPM's to see if it was charging but no luck. Do I need to run an indicator lamp (with diode) to get this thing to start charging?

 

[reddingcruiser]

There is always the chance the alternator was DOA. If you can't get it to charge, take it off and have it bench tested.

I've had them bad right out of the box.

 

[4x4veteran]

There is always the chance the alternator was DOA. If you can't get it to charge, take it off and have it bench tested.

I've had them bad right out of the box.

Or you might have blown a diode in the alt. when wiring it up.
Either way it could be a bad alternator.
Have you tried touching a hot wire to the lose white wire with the engine running to see if it shows a charge on the gauge?
I take it the heavy cable attached to the bottom of the alt. is a ground to the frame/block or directly to Batt?
What is the other lose cable on the right go to?
If you don't have any warranty on the alt. you can buy a new bridge and replace it then wire it up like we told you and see if that fixes it.
NOTE; always disconnect the battery when working on the electrical or anything else for that matter.

I pulled the intake on the engine a week ago and after I got everything back together the idiot light wouldn't come one.
I found that the exciter wire right at the junction on the alt. had broken from age and being moved around while working on the engine.
Check continuity on all the wires just to be sure it isn't that simple.

 

[shelfboy1]

ive had several gm vehicles where they jumpered the 2 small wires with a plug .now i do that on all my trucks using that style alternator . i think it may havebeen thier version of a 1 wire until they got one into production

 

[jvincig01]

ive had several gm vehicles where they jumpered the 2 small wires with a plug .now i do that on all my trucks using that style alternator . i think it may havebeen thier version of a 1 wire until they got one into production

Are you saying to connect both the white and red wires like this?

 

[jvincig01]

Or you might have blown a diode in the alt. when wiring it up.
Either way it could be a bad alternator.
Have you tried touching a hot wire to the lose white wire with the engine running to see if it shows a charge on the gauge?
I take it the heavy cable attached to the bottom of the alt. is a ground to the frame/block or directly to Batt?
What is the other lose cable on the right go to?
If you don't have any warranty on the alt. you can buy a new bridge and replace it then wire it up like we told you and see if that fixes it.
NOTE; always disconnect the battery when working on the electrical or anything else for that matter.

I pulled the intake on the engine a week ago and after I got everything back together the idiot light wouldn't come one.
I found that the exciter wire right at the junction on the alt. had broken from age and being moved around while working on the engine.
Check continuity on all the wires just to be sure it isn't that simple.

I havent tried touching the white wire but i will tonight. The gauge on the dash isnt connected but I can still test.
The thick wire is a new ground connected to the frame. The other one off to the side is the old ground to the block. I thought that might have been the issue.
Fortunately I do have a warranty but it's sort of a hassle because I bought it from a buddy who works at a parts supply 2 hours away.
I will definitely disconnect the battery first, I have heard crazy stories about people frying things.