Alternator not Charging

[toddgreene]

Please help me with my OEM Alternator...

I have the "charging wire" running from the post on the alternator directly to the positive battery terminal. (One-wire) The alternator does not charge, or at least the engine stops when the hot cable is disconnected. This alernatoer is brand new and the second I have tried.

I assume the alternator grounds into the block like most???

Thanks,

Todd

[jinxcrx]

Did you check the fuse?

[toddgreene]

Did you check the fuse?

Thanks,

I have it wired directly to the battery... no fuse.

Thanks again,

Todd

[CRXsi]

Sorry...I'm a little confused by your post and procedure for testing?

At any rate when the car is running, take a voltmeter and put on the battery + and -. You should have roughly 14.5V with it running. If you only have 12V or less then your alternator is not charging. Once that is confirmed then you need to make sure the field wires are hooked up (plastic connector with usually 2 or 3 wires) to the alternator.

Post back with these results and we'll continue with diag from there.

[Greg Amy]

Thanks,
I have it wired directly to the battery... no fuse.

Uuuhhh, probably not a very smart thing to do. Accidentally ground that wire and at best you'll fry the wire, but at worst - and more likely - you'll explode the battery. Acid makes a real mess in an engine compartment...

But, to your question, do you understand how an alternator works? I ask this not to be snide, but to understand what you're asking.

Generally speaking, an alternator has two circuits: the charging circuit and the field circuit. The charging circuit is where all the current is going to the battery/car, and the field ("sense") circuit is something the alternator uses to decide how many volts to apply to the charging circuit. Is the field circuit is not getting voltage, then the alternator does not put out any juice; conversely, if the field circuit sees, for example, 17 volts it'll back off the alternator charge circuit to get to ~14.5V.

I'm inferring from your posts you're rewiring the car away from stock. If so, you need to understand what each connection to the alternator does before you start(ed) making changes. Rewire it improperly and you can blow-up your alternator (or, worse, pound 25V into your car and blow up other parts). Bring your alternator to a parts store and they can test it for you; if it works fine then you've re-wried it incorrectly... - GA

[toddgreene]

Sorry...I'm a little confused by your post and procedure for testing?

... you need to make sure the field wires are hooked up (plastic connector with usually 2 or 3 wires) to the alternator.

Post back with these results and we'll continue with diag from there.

Thanks,

My testing was the old fashioned method... Disconnect the battery while the engine is running to see if car is running on battery or alternator.

I do have the plastic harness disconnected. The are the wires that went to the alternator light in the dash, the choke sensor for the factory carb (White-Blue wire) and the fan temp switch (Black-Yellow Wire). I have a Weber carb, so I got rid of everything related to factory carb and emmisions. I have installed an aftermarket fan and rewired for it. Do the White- Blue and Black Yellow wires need to be connected or grounded for the voltage regulator to work?

Thanks again,

Todd

[toddgreene]

Thanks Greg,

Good point about the fuse! I was trying to keep things simple.

I thought I understood the alternator but did not realize that about the "field circuit".
Does the alternator make its own power for this circuit? or come from nother source?

I have disconnected what is probably the field harness from the car. It connected to the alternator lamp in the dash, the choke sensor for the factory carb and another wire to the fan timer switch. Checking the wiring diagram, it appears the Black-Yellow wire from the factory fan timer switch brings power "in". It appears that the choke sensorwire (Blue-White) is the eventual ground. Does this make sense?

Do I need to bring power into the field circuit via this same path?

Thanks again,

Todd

[Greg Amy]

I do not know your car, and I do not have a wiring diagram, so I cannot offer specifics. However, the field circuit wire - generally speaking - simply needs to be attached somewhere in the electrical system where it can "sense" battery voltage (I am assuming your alternator has an internal voltage regulator).

Two other points:
- Alternator-equipped cars will not run with the battery disconnected;
- Place an appropriately-sized fuse on the battery end of that large wire between the alternator and battery.

Side question: why are you going to all the trouble of re-wiring this car? The factories usually do a damn fine job of it. Secondarily, if this is an IT car you're prepping, making these changes - even for "simplicity" - is likely contrary to the rules (though the new ECU wiring rules make that a gray area).

It's certainly contrary to your well-being and sanity... - GA

[toddgreene]

I do not know your car, and I do not have a wiring diagram, so I cannot offer specifics. However, the field circuit wire - generally speaking - simply needs to be attached somewhere in the electrical system where it can "sense" battery voltage (I am assuming your alternator has an internal voltage regulator).

Two other points:
- Alternator-equipped cars will not run with the battery disconnected;
- Place an appropriately-sized fuse on the battery end of that large wire between the alternator and battery.

Side question: why are you going to all the trouble of re-wiring this car? The factories usually do a damn fine job of it. Secondarily, if this is an IT car you're prepping, making these changes - even for "simplicity" - is likely contrary to the rules (though the new ECU wiring rules make that a gray area).

It's certainly contrary to your well-being and sanity... - GA

Thanks Greg,

You got me pointed in ther ight direction with the field circuit explanantion.I also need to fuse the charging circuit to the battery.

Growing up in te country and working on older cars, the battery disconnect test was a way to test whether the alternator or battery was bad on a car on a dead car. Jump start the car, while running, if you disconnect the positive cable, if the car still runs, it is running off the alternator and the battery is bad. If the car dies, it was running off the battery and the alternator wasn't charging the battery. It always works on old British cars and old Fords. I am new to these "modern" cars like 1987 Hondas.

I actually haven't re-wired everything. I have tossed the OE gauge cluster and changed the radiator and fan, which apparently affects this. I wired the Alt directly to the battery to put the ALt output on the battery side of the master-switch.

You are absolutelty correct about tha sanity. I am heading to school in Memphis later this week and just realized yesterday I have this charging problem . Better now than Friday.

Thanks again,

Todd

[toddgreene]

Thanks Guys!!!
That field circuit lesson did the trick.

Todd