When does the alternator turn on the idiot light?

When the engine starts and gets up to a high enough rpm for the alternator to start putting out voltage, there is a diode inside that takes some of the output voltage and featured back to the terminal that goes to the idiot light.

Is it normal for alternator voltage to be 13.8?

Some may disagree but anything over 13 means its charging the battery. I’d be replacing alternators left and right if I needed 14. 13.8 v is within the normal charging range. If you measure it right after you start the engine after the car sits overnight it might read in the 14’s, but will return to the 13.8 v range over time as the engine runs.

What does 13.8V mean on a car battery?

When you see 13.8 on your battery with the car running that means the battery is fully charged. In solar power systems with 12v batteries 13.8 is called the float charge. Battery is fully charged and the charge controller is maintaining it at the prime voltage for battery health.

What causes an alternator to output low volts?

If the voltage at the battery and alternator don’t match. For example the battery reads 12v and alternator reads 14v. This means that there is an issue with wiring. While applying the same conditions as above.

What does it mean when battery and alternator don’t match?

Also the voltage at the battery and the voltage at the alternator should be within 0.5v of each other. If the voltage at the battery and alternator don’t match. For example the battery reads 12v and alternator reads 14v. This means that there is an issue with wiring. While applying the same conditions as above.

What happens to an alternator when a light bulb is burned out?

In fact, the alternator may fail to charge if that light bulb is burned out. When the engine starts and gets up to a high enough rpm for the alternator to start putting out voltage, there is a diode inside that takes some of the output voltage and featured back to the terminal that goes to the idiot light.

What to do if your alternator has low voltage?

Put the black multimeter probe on the negative battery terminal (if possible dig it into the battery post, not the terminal). Put the red probe on the alternator case. Your looking for the voltage to be below about 0.5v. If the voltage is higher than that examine all the negative cabling for problems. Preform the same test with the positive side.

Why does my alternator get higher than base voltage?

You should get 0.5 to 2 volts higher than base voltage. If you are getting more than 2 volts above base voltage, most likely your alternator is over-charging the battery or the battery is faulty. Other potential problems are a faulty voltage regulator or a problem in the charging system wiring.

How can I tell if I have an alternator problem?

To differentiate an alternator problem from the battery, you will need to use a voltmeter to check for voltage. First, turn off the engine and check the battery voltage. A fully charged battery should have a reading of 12.65 volts. Next, turn on the engine and recheck the voltage. You should have a reading of 13.5 to 14.5 volts.

Where is the volt meter on an alternator?

To diagnose the problem, put the positive wire of your volt meter on the alternator output terminal and the negative wire of your volt meter on the battery plus terminal. Put some load on the battery, such as lights or something, rev the engine, and see how much voltage is getting dropped between the alternator output and the battery terminal.

How does an alternator work on a lightbulb?

What is happening is that the alternator is full output voltage is getting sent to one terminal of a lightbulb, and the other end of the bulb is connected up to the battery positive terminal through the ignition switch, which is now at a lower voltage because of the voltage drop in the positive wire.

Why does my alternator light get brighter when I Rev the engine?

This voltage drop causes the light to light, and also results in the battery charging poorly if at all. Usually when this is the case, the light will be very dim at hiatal and will get brighter as you rev the engine.

Why is the alternator light dim at hiatal?

Usually when this is the case, the light will be very dim at hiatal and will get brighter as you rev the engine. To diagnose the problem, put the positive wire of your volt meter on the alternator output terminal and the negative wire of your volt meter on the battery plus terminal.

How does an IDJIT light work with an alternator?

The idjit light essentially goes from the alternator output to the battery positive. If all goes well, both terminals are at the same voltage potential and no current flows. If either the battery or alternator are not at the same level, there will be current flow through the light and it will illuminate.

Is there a test light on the alternator wire?

However, here is the weird part: With the EXC wire disconnected at the alternator, I can put a test light on the end of the wire and to the battery negative. This completes the circuit again and the dash light comes back on, but the test light does not light up.

Why does the IGN light go out on an alternator?

If I disconnect the EXC wire at the alternator, the ign light goes out on the switch panel. So this is telling me that no wires were crossed, etc.

What happens if I Disconnect the EXC wire at the alternator?

If I disconnect the EXC wire at the alternator, the ign light goes out on the switch panel. So this is telling me that no wires were crossed, etc. However, here is the weird part: With the EXC wire disconnected at the alternator, I can put a test light on the end of the wire and to the battery negative.

Where does the warning light wire go in a car?

If your car has an alternator, the warning light wire connection depends on whether the alternator is fitted with an internal or an external voltage regulator. If the alternator is fitted with an internal regulator, the wire you want connects directly to a terminal on the back of the unit marked WL or IND.

When does the alternator turn on the idiot light?