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Fri Nov 10, 2023 11:11 am

Driving the alternator light came on and stays on. Prior to that when turning on the turn signal the alternator light would flash a little red.

Alternator has 1500 miles on it and is a year and a half old. It's wired like the picture below, I have electronic ignition and fuel injection.

Checked all wiring at battery, alternator and dash. All connections are good. Light on dash comes on with the key off and connecting to ground.
Checked battery voltage at idle and 1500rpm, 11.7 and dropping
Connected battery charger set to 2A charge and instantly tripped the batt chg circuit breaker.
Used an Ohm meter to checked the + battery terminal to a random ground point thinking maybe it's a cut wire somewhere but, no. Infinity on the ohm meter.

What could be causing the battery charger to trip instantly? Voltage regulator melted?

Thank you in advance for your input.

M

Fri Nov 10, 2023 12:10 pm

What happens when the battery is disconnected from the car, and then hook charger to the battery?

Fri Nov 10, 2023 12:27 pm

The battery starts charging and stays charging.

Fri Nov 10, 2023 5:06 pm

Is that the ignition switch with the "15", "30" and "50" circuit numbers in that circle?

And what is the big red dot in the D+ feeder? It looks like there is a bulb, too?

Something don't look right on that D+ circuit.

Fri Nov 10, 2023 5:27 pm

Yes, that’s the ignition switch. The large red button is the alternator light added to the dash and the bulb is to trigger the alternator to start charging. I got this schematic from somebody on the samba. He said it’s the way it Hass to be to work with the fuel injection computer.

The car ran fine like this for 1500 miles.

Fri Nov 10, 2023 5:32 pm

Michaellatini wrote: Yes, that’s the ignition switch. The large red button is the alternator light added to the dash and the bulb is to trigger the alternator to start charging. I got this schematic from somebody on the samba. He said it’s the way it Hass to be to work with the fuel injection computer.

The car ran fine like this for 1500 miles.

Okay. So, there are 2 bulbs. The big red dot and the bulb drawing? Trying to understand.

Going out to the brewery for several pints. When I get back I will respond if I can! Cheers!

Fri Nov 10, 2023 5:36 pm

Michaellatini wrote: He said it’s the way it Hass to be to work with the fuel injection computer.
Reconsider any advice this person offers in the future, Fi works exactly the same as any other system, it does like to have the alternator charging though, that complex and confusing diagram makes no sense, how did millions of these cars manage with the factory wiring?

Fri Nov 10, 2023 5:36 pm

Thank you Jimbo. Have a good evening.

Sat Nov 11, 2023 11:07 am

The tripping of the circuit breaker on the charger was operator error! Nicked the battery hold down. Still not charging.

Must be a bad alternator. Paid $189 for it.

Sat Nov 11, 2023 2:18 pm

Michaellatini wrote: The tripping of the circuit breaker on the charger was operator error! Nicked the battery hold down. Still not charging.

Must be a bad alternator. Paid $189 for it.

That sucks! But good that you figured that out. Could have been a long rabbit hole!

How are you testing the alternator output?

Sat Nov 11, 2023 3:25 pm

Volt meter at the battery when running.

Sat Nov 11, 2023 3:32 pm

Michaellatini wrote: Volt meter at the battery when running.

Yes, but what is the field wire doing? Does the idiot light come on with the key on? Then go out when the engine starts? Or what is it doing?

What is the voltage Key off, at the alternator B+?, key on is?, once running?

Sat Nov 11, 2023 3:53 pm

Voltage drops running. Key on voltage is whatever the battery is at. Idiot light comes on when key is on not running.

Sat Nov 11, 2023 3:54 pm

Oops. Light stays lit when running.

Sat Nov 11, 2023 4:03 pm

Michaellatini wrote: Oops. Light stays lit when running.

Yep, the field wire is not functional or the regulator is not functioning.

Maybe try running it as designed. Not tied into the fuel injection system. Just to test the alternator, if it is possible. If that is possible. I do not get why the module wants to know or control field power. Odd. Thinking it is a fail safe.

Sat Nov 11, 2023 4:07 pm

It’s wired the way it was shown to me. It ran fine for 1500 miles but, that’s not good.

Sat Nov 11, 2023 4:11 pm

Are you thinking that the way it’s wired could be causing the alternator to give up quickly?

Sat Nov 11, 2023 4:42 pm

Michaellatini wrote: Are you thinking that the way it’s wired could be causing the alternator to give up quickly?

I have never seen a system wired like that, so…..I am suspicious of it. It might be okay to an engineer, but to my “in the trenches” viewpoint, it looks like an issue.

That is why I say to bypass it, if possible. Test and verify.

Sat Nov 11, 2023 4:57 pm

Ohhhhh I’m not thinking! It was wired that way because the red light in the drawing was an LED. The incandescent light was to trigger the alternator but it did not work so I change the LED to another incandescent. I need to remove the second bulb. Yeesh!

Sat Nov 11, 2023 4:59 pm

From the diagram I gather there are two (2) GEN lamps? The red circle is the dash mounted GEN lamp? Is it an LED bulb? The second bulb marked "ALT/GEN LAMP" is that an LED or incandescent bulb?

What are the two bulbs wattage ratings and are they LEDs?

The stock alternator was meant to have an incandescent 12v/2W bulb in the circuit to the D+ terminal. As an incandescent bulb, current would flow in either direction lighting up the bulb. When trying to use an LED bulb for the ALT/GEN lamp you run into a problem as many LEDs typically only allow current flow in one direction as they are physically diodes (some of the larger LED bulbs are not polarity sensitive). The above diagram looks like an attempt to use an LED in the dash but still provide the full 2-way current flow thru the secondary (incandescent) bulb.

Michaellatini wrote: Voltage drops running. Key on voltage is whatever the battery is at. Idiot light comes on when key is on not running.

Oops. Light stays lit when running.
Which GEN lamp remains ON? Both?

Ok, a few tests are in order...
1) Disconnect all wires from the D+ terminal of the alternator but leave the B+ connection to the battery connected. Place your VM on the D+ terminal of the alternator and measure the voltage coming our D+. It should be less than 1.0v. Anything higher than this means an internal diode has failed in the alternator and it must be replaced/repaired. When this happens the GEN lamp tends to remain ON even when the key is OFF.

2) Rig up a simple jumper wire with an incandescent 12v/2W bulb in the wire. Steal one from the speedometer. Tab power from a constant 12v+ source near the alternator (the B+ would count) and with the 2W bulb inline power D+ thru the 2W bulb. Since your power source is constant 12v the bulb should remain ON as long as the engine is not running. Start the engine and the inline bulb should turn OFF. Measure the voltage at the B+ terminal of the alternator and the battery terminals. You should get something between 13.8v ~ 15.0v. Rev the engine to 2100rpm and check again.
If you still get voltage readings only around the typical 12.6v or lower your alternator is not charging and it has nothing to do with the odd D+ wiring.

If your alternator is charging with this inline bulb, shut the engine down and remove the jumper wire/bulb. Connect just one of the bulb circuits to D+ and re-run your tests. Retest with just the other bulb. Then retest with both connected. Report back what you find.