How to diagnose an alternator or electrical problem?

Diagnosing alternator problems can be a bit tricky because the electrical system in a car comes from two places, the battery and the alternator. I’ll give you a little background so you can understand what both systems do. The battery has one primary function, which is to start the car.

What does it mean when your alternator stops charging the battery?

Indicator Light On. Usually, the first sign that your charging system is in trouble is a “battery,” “ALT,” or “CHARGE” warning light illuminating on your instrument panel while driving. It means that for some reason, the alternator has stopped charging the battery and your car is running on battery power.

What should the resistance be for an alternator?

If all this checks out then I suspect you have a wiring issue. I would perform either a voltage drop or resistance measurement of each of the wires from the PCM to the alternator. Also, through the fusible link from the battery to the alternator. You should have less then a half ohm of resistance.

What happens when the diodes in an alternator go bad?

Alternators use diodes to rectify alternating current produced by the alternator into direct current. When one or more diodes go bad, the alternator can cause all kinds of problems. AC voltage leak can cause your lights to dim and drain power from your battery, for example.

When does a car battery have a bad alternator?

If your car engine shuts down immediately it starts or after a short drive, then your alternator has malfunctioned and is not charging the battery the way it should. If jumpstarting your car works and the car keeps running fine, but the vehicle does not start again using its power, then you have a dead battery on your hands.

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.

What does it mean when an alternator light comes on?

If the light illuminates only intermittently, it usually indicates a loose or worn drive belt or serpentine belt, worn-out or bad carbon brushes in the alternator. But remember that the light doesn’t always mean there is a bad part; the light may be triggered by a sensor giving a wrong message or there’s something wrong with the circuit itself.

What happens if you have a bad alternator in your car?

The car won’t start at all. If the problem is a bad alternator, your car will slowly lose power. You’ll be driving down the road, your lights will dim, and you’ll lose power and die. If the problem is with your battery, then you’ll generally only have trouble starting your car since that’s the battery’s main function.

Can a Saab 92 start with a bad alternator?

Dual ignition coils (the blue cylinders at the top of the picture) on a Saab 92. Before you go out and order a new battery or alternator, test some of these different systems. If your alternator, coil, battery, or starter is bad, the car probably won’t start, and it definitely won’t be drivable.

What happens if you have a bad solenoid or starter?

Solenoid or Starter. If the problem is a bad alternator, your car will slowly lose power. You’ll be driving down the road, your lights will dim, and you’ll lose power and die. If the problem is with your battery, then you’ll generally only have trouble starting your car since that’s the battery’s main function.

What should I do if my alternator is not charging?

The alternator normally lasts longer than the battery. There are some easy steps you can go through to check the function of your alternator. Tap the alternator carefully with a hammer while the engine is runnin; if the charging goes back to normal, the coals inside it are worn out.

Is the alternator at the heart of the charging system?

Dan Ferrell writes about do-it-yourself car maintenance and repair. He has certifications in automation and control technology. The alternator is at the heart of the charging system of your vehicle. Alternator problems and charging system problems can affect your vehicle in different ways.

What causes an alternator to go over 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 do I know if my battery or alternator is bad?

Signs of a bad alternator. If the above steps reveal that the battery is working, it’s time to take a closer look at the alternator. There are certain signs of a bad alternator to look for: While running the car, note the brightness of the interior lights. If the dashboard gradually dims, the alternator is likely at fault.

Will a car run with a bad alternator?

Yes , a car will run with a bad alternator……until the battery goes dead. Yes but eventually the car will die when the battery no longer has power to run the spark plugs and other systems. If you shut the car off , it will likely not start again without a jump start.

What happens if my alternator overcharges?

An overcharging alternator will cause the voltmeter on the vehicle’s dash to read an overly high voltage that may or may not vary with engine speed. Normal readings should be high upon start-up, then settle into the normal range. An overcharging alternator, however, will cause the meter to remain in the high position after initial start-up.

What causes an alternator to over charge?

What causes an Alternator to Overcharge? Step One. Battery – Alternators that overcharge will typically produce excess voltage to the battery, making the battery case swell up, become very hot and lose its electrolyte through boiling. Step Two. Step Three. Step Four. Step Five.

Is the alternator the only thing that powers the car?

Many people assume that the car’s battery is the only thing that powers all electrical components in the car. But, this is not true. The alternator plays a vital role in supplying power to the car’s AC, recharging the battery and ignition.

Where does the alternator drive belt drive the engine?

The ease of gaining access to the brushes indicates the potential for DIY brush changing. This is often very successful, but if the slip rings are worn the brushes might suffer very rapid wear. Always try to inspect the slip rings when changing brushes. The alternator drive belt drives the alternator from the engine crankshaft.

Where are the bolts on the alternator bracket?

Move back down under the car to the alternator bracket. There are nine bolts (including the engine mounts) holding the alternator bracket to the engine. At the front of the engine you will need to remove two 13mm bolts along with a T45 Torx bolt.

How does a voltage sensing circuit work on an alternator?

The voltage sensing circuit should really be considered a voltage correction circuit or a voltage drop compensation circuit. The voltage sensing circuit works by utilizing these smaller sensing wires in order to compensate for the voltage drop in the larger alternator output wires.

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.

Which is the best alternator for a truck?

DB Electrical ADR0217 New Alternator 4.3L 4.3 4.8L 4.8 5.3L 5.3 6.0L 6.0 1500 2500 Silverado Sierra… DB Electrical AKT0001 for Ford 8N 2N 9N Tractor Alternator For Generator Conversion Kit 1939… DB Electrical New ADR0152 Alternator for 1 Wire Universal Self-Excited 10Si 10 Si 63 Amp/Internal…

What causes an alternator pulley not to work?

Not replacing it on time, stuck alternator pulley or a faulty bearing are common causes of this problem. Worst thing about this problems is that it can snap at a moments notice. Main causes of alternator problems (at least from what I’ve seen) are: This is the first and most common reason of them all.

Can a loose tensioner cause an alternator to fail?

Nevertheless, if the tensioner wears out, it can cause alternator problems (loose belt or worse, the belt can totally fall of the alternator pulley). Broken or damaged wires This happens mostly in older cars duo to material fatigue of the electric installation.

What does it mean when your alternator is not charging?

If the alternator is not charging the battery, you will have a red “ALT” or “charge” sign on your dashboard. This means that your battery is no longer being supplemented for power by the alternator. You will need to recheck the wiring because the light could also be faulty.

What should my battery gauge be at with engine off?

The battery is putting out plenty of volts on it’s own with engine off. Before the light comes on and the gauge falls to 0, my battery gauge hovers at 12; meaning, the needle will move to just before or just after the 12V hash line intermittently

What happens when the alternator of a car is dead?

The alternator and the car’s battery work hand in hand. A good battery should give you service for the next five years before its lifespan ends. If your battery is dead, then it will not give power to the car’s alternator. The alternator normally lasts longer than the battery.

Why does my car not start when I jump the alternator?

If jump starting gets your engine started and running, but the car will not start again once you turn it off, the battery is probably the problem. In this case, the alternator is doing its job of keeping the battery going once it has been jumped, but the battery can’t hold a charge when the alternator is shuts off.

What happens if the alternator doesn’t charge the battery?

Finally, the alternator completes this cycle by charging the battery. Using the process of elimination, find the culprit by bypassing the battery’s role and jump-starting your car. If the engine starts but dies immediately, your alternator probably isn’t keeping your battery charged.

When to replace battery, alternator, or starter?

When you check these three, always start with the battery. It’s most often the part that failed, and it’s also the cheapest part to replace. A car battery should last about four to five years. It is not made to hold a charge for that long, so it gets recharged by the car’s alternator while you drive.

When do you know something is wrong with your alternator?

If the battery is good, then there is likely something wrong with the alternator. Dim Lights: If you notice your headlights or other lights dimming or flickering, this can indicate that they aren’t getting enough current. Generally, the dimness will worsen as the alternator wears.

Can a load test alternator be overheated?

Although load-testing an alternator provides a quick way to test for drive belt slippage, keep in mind that an alternator can easily be overheated when testing for maximum output during low-speed operation for an extended period. Most alternators wi

Is it normal for an alternator to not charge?

Still, it’s perfectly normal for others to see the alternator not charge at all intermittently. One test is not enough if you are diagnosing a charging system problem. All too often, the alternator is condemned as the source of the problem if only battery voltage is present with the engine running.

Can a bad fuse cause an alternator to go bad?

Bad Fuse – Some vehicles use fuses to keep the alternator functional. These fuses blow out after a while or when there is a power surge. In these cases, your alternator would fail and your battery would not charge. If you have a bad alternator, look in the owner’s manual to see if there is a fuse in your car.

Why does the alternator make noise when the car is stationary?

Alternators can make noise, due to defective bearings, belt, etc., and still charge the battery. If you are hearing noise from the area of the engine when the car is stationary, if the sound is not really obvious, that is… Hi there. Putting a penny in place of a fuse, not recommended, replace with the correct fuse.

What does it mean when your alternator is whining?

Your car can also make a whining sound when the voltage regulator is sending signals to the alternator to charge more than is necessary. If you hear any type of whining or grinding sound that’s a good indication that your alternator needs to be checked.

When does the alternator warning light come on?

The Chicago Tribune reports that if the alternator has failed, a warning light will normally come on. Most vehicles have a specific light that is battery shaped that will come on to signal if there is an issue.

Why are brushless alternators good for a car?

High efficiency models deliver measurable fuel savings over the life of the vehicle, and alternators equipped with Remote Sense dramatically improves battery charge time. The unique brushless designs deliver the durability you can count on.

Is the odometer flickering at idle or idle?

It will also do it slowing down to a stop, but it does not do it at idle. The flickering of the odometer and parking indicator that you see is just from my camera. You cannot see the fast flickering that they are actually doing.

What are the ratings of Delco brushless alternators?

Brushless alternators feature fewer moving parts and come standard with a 3 year warranty (applies to US and Canada) and are available with Remote Sense. The 36SI is available in output ratings up to 170 amps and comes in J180 and pad mounting configurations.

What kind of voltage does an alternator need?

All alternators have a voltage regulator circuit which keeps the voltage at the ideal 13.8 to 14.2 volts needed to run the car and charge the battery. Most newer vehicles have a voltage regulator which is part of the alternator, but older vehicles have the regulator as a separate part.

How long does it take to install an alternator?

If you need to have it installed by the mechanic, then the price might be a bit higher. Depending on where your alternator is located within the compartment, the installation might only take an hour. But if the alternator is difficult to access, it might require removal of other parts and it could take many hours.

How many volts does a 14 volt alternator need?

The actual voltage regulator set-point is typically between 14.1 and 14.8 volts and that is why an alternator may be referred to as a 14 volt alternator instead of a 12 volt alternator. The battery needs to receive 14+ volts in order to maintain its charge. The same rules apply for a 24 volt system.

What are the symptoms of a bad alternator?

In rare occasions the service engine soon light may light up. Also, some vehicles have an “alt” light that specifically tells you there is a problem with the charging system, and not the battery itself. Outside of the battery warning light, a dead battery is the most common symptom of a bad alternator.

How many volts does Chevy Silverado alternator need?

With the engine just fired up, you should get over 14.2 volts. If you got 14.2 or more volts, the alternator is charging fine. If it’s still showing in the 12’s, it’s time to replace the alternator.

What is the diagnostic code for bad throttle position sensor?

Using a code reader, you should be able to confirm whether a faulty TPS is the culprit or a different component. Diagnostic trouble codes P0120, P0121, P0122, P0123, and P0124 are what will commonly appear. The engine can stall for no reason and without any warning. This happens when the TPS gives incorrect information to the ECM.

What to do if your alternator is not charging?

Turn on the radio. Turn on as many things as possible in your car or truck (the reading should start to go down hill to 9 Volts or less in about a minute’s time. The vehicle may stall below 10 Volts). Turn off the vehicle. If the test gave you the results stated above. The alternator is not charging the battery. Why?

Can a battery negative terminal test an alternator?

The same test can be repeated using the battery negative terminal and the alternator housing to check for excessive resistance on the ground side of the circuit. If the wiring checks out okay, the problem could be in the voltage regulating circuitry inside the powertrain control module.

How to test an alternator with a multimeter?

TEST 1: How To Test The Alternator With A Multimeter. You can remove the discharged battery and replace it with a fully charged one or simply charge the vehicle’s battery (on the vehicle or off) before test. O.K., the test is divided into three parts: PART 1 – Testing the alternator voltage output with the multimeter in VOLTS DC mode.

How to replace an alternator on a 1995 GMC?

Somewhere on your vehicle there is a tensioner pulley. You’ll need to move it enough to slip the belt off the pulley. Our ’95 GMC has a standard spring-loaded GM tensioner that required us to pull it back with a wrench.

What’s the best way to replace an alternator?

There’s a 90-degree twist in the middle of the Cross Force wrenches, so you end up pushing on a flat surface. The result: we could push harder without discomfort. So we just laid into it and the belt came free. Once the belt is off just remove whatever bolts connect the alternator to the bracket and you’re good to go.

What’s the best way to rebuild an alternator?

Use an ohmmeter to assure that the diodes are receiving the proper current. Replace the plastic cover as well as both of the resistors. Put the alternator back in the vehicle. Reconnect the electrical leads assuring that you’re installing them properly. Replace the serpentine belt.

What should I do if my alternator is hot?

Really! First and most importantly: disconnect the battery. There may be several wires or just one wire on your alternator, but rest assured that one of them is hot. If you don’t disconnect the battery, you’re very likely to end up grounding a live wire during the process.

How many bolts do you need to replace an alternator?

Our model required the removal of three bolts: one at the front and two at the rear. With the old alternator in your hand you’re half way home. You’ll likely find getting the new one back in goes much faster since you already know what size the bolt heads are and where everything is.

What should I do before installing a new alternator?

Your battery should have been disconnected before you installed the new alternator. Make sure your car battery has the proper capacity for your vehicle and that it is fully charged. If the battery is defective in any way, your alternator will fail well before its time. If the battery is discharged, your alternator will only have a short life.

What happens if you have a new alternator and the battery is not charging?

The alternator in your car is an integral part of your vehicle’s electrical system. If you have a new alternator and the battery is still not charging, then you definitely have some kind of a problem with your battery that you’ll need to address immediately.

What causes an alternator to stop working on a car?

Once the alternator stops working, so do all of the electrical systems required to keep a car going. Other problems can also cause a car to not start. It could be a bad starter, corroded cables, or a broken connection somewhere between the battery and starter.

When is it time to get a new alternator?

When it feels like your car’s battery just can’t stay charged, it might be time for a new alternator. The Drive and its partners may earn a commission if you purchase a product through one of our links. Read more.

Where is the alternator located on a car?

The alternator uses magnets that spin to create an alternating current that converts energy into electricity. It’s usually found on the front of the engine and is driven by the crankshaft via a serpentine belt. Symptoms of a Bad Alternator Your car can communicate with you in many ways, especially if there’s something wrong.

Can a bad battery cause an alternator to over charge?

Make sure that all the connections to the alternator, remote voltage regulator (if applicable) and battery are clean, tight and in good condition. Check your battery or have it tested at your local auto parts store. A bad battery cell can cause the alternator to over-charge the good battery cells.

What to do if your guage is going crazy?

Check the ground cable at the frame under the driver’s seat. Clean it and make sure it is secured good. Does it work OK with the light off-? If so- could be a short in the trailer plug– or the cable that is behind the driver side– on top of the gas tank– (That is for a 5th wheel plug if the person wants to add one.)

Why do my gauges sweep to Max and back when I start my truck?

09 and newer trucks do this everytime at startup while 08 and older (not sure of how old but wanting to say 97) do this on two conditions. 1. Bad battery or alternator. 2. You’ve entered the dealer ic test mode (some call it engineering test mode). It’s purpose is for the gauges to find their min and max points of their ranges.

Can you use an amp gauge on an alternator?

Amp Gauge Wiring 1) Always disconnect the ground lead from the vehicle battery before wiring any gauge. 2) Classic Instruments’ Amp gauge should only be used on vehicles with alternators rated at 60 Amps or less. Using an alternator with higher output capacity is dangerous and could cause a fire.

Can a volt gauge be used on classic instruments?

2) Classic Instruments’ Amp gauge should only be used on vehicles with alternators rated at 60 Amps or less. Using an alternator with higher output capacity is dangerous and could cause a fire. A Volt gauge is available for systems using alternators rated higher than 60 amps.

Why does my car not start with a new battery and alternator?

With a new starter, battery, and alternator (assuming you have not drained the battery attempting to start it), the starter should attempt to crank over the engine. If the starter does not make any noise when the key it turned to crank over the engine, you have an issue with the fuses, or the circuit.

What should the charge voltage be on an alternator?

Turn on the high beams for 10 seconds and then turn them off. Measure battery voltage across the battery posts with your DMM. You should get between 12.4 and 12.6V. This means your battery is fully charged. If you get a reading below 12.4V, charge the battery before continuing. 5b. Measure the Charging System’s No-Load Voltage

Can a car battery be drained by an alternator?

While you might initially think that any problems with electrical things like lights or radio not working are directly related to the battery, the alternator is actually where most of the power in your vehicle comes from. Consider that if you were to leave the lights of your car on overnight by the next day your battery might be drained completely.

Can a bad car battery cause an alternator to not charge?

In theory a car can run only with the alternator charge, but this can cause heavy voltage spikes and other strange symptoms so this means that a bad car battery can cause an alternator to not charge also. Cars are increasingly coming with modern electronics.

Is the battery voltage on both sides of the alternator?

If you clear the codes and the warning comes back lets make sure the fusible links have power on both sides. Here is a guide and the alternator wiring diagrams to help you test and see how the system works. Check the two fusible links in picture they should have battery voltage both sides. The problem may be the PCM but lets run some tests first.

What happens when the belt on an alternator breaks?

A closer observation of the alternator will reveal a pulley and belt system that works to convert mechanical energy into electrical energy. The serpentine belt powers the alternator, and if it fails, the alternator will stop working the moment your belt wears out and breaks, or the pulley becomes damaged.

What to do if your alternator is over charging the battery?

Ask an assistant to start the engine and hold engine speed at about 1500 RPM. Measure voltage across the battery with your DMM. 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.

What does a positive lead on an alternator mean?

They are earth connections. All the positive leads should give readings of battery voltage . If there is a small lead marked ‘Ind’ for the ignition warning light, and it alone remains dead when the ignition is switched on, the light mat have blown or be disconnected.

How much does it cost to replace an alternator?

Alternator Prices and Installation. Make sure that your current alternator is beyond repair first before getting a new one. Alternator prices can vary greatly by make and model, but generally speaking, new alternators should run around $250 without labor for installation.

What’s the best way to test an alternator?

Begin testing the alternator – Now you are ready to begin the actual testing. First turn the engine off. Connect the voltage meter – Turn your voltage meter on and set it to DC volts, place the positive lead to the positive (+) terminal on the battery and the negative (-) lead to the negative terminal on the battery.

Why did my Honda alternator fail a test?

They hooked up the test tool and said that the battery was good, starter was good, but the alternator is bad because the voltage regulator test failed. I called the Honda dealer near me and ordered a new alternator. The wait time was 1 day.

Why is the voltage reading on my alternator going up?

While watching the voltmeter display, start wiggling wires at the back of the alternator, the battery, and the remote voltage regulator (if there is one). If the voltage reading on the meter display goes up while wiggling one of the wires, you’ve found a bad electrical wire or connection.

Is it a case of your alternator being possessed?

Is this a case of your auto being possessed? No. Most likely it’s one of many possible alternator problems, and without some attention, the alternator can cause car trouble ranging from slow starts all the way up to a dead car.

Where does the energy from the alternator go?

The alternator takes the energy from the crankshaft and turns it into the electricity that is stored in the battery of your car. When your car is running the alternator helps to power the different electrical systems in your car and keep your battery charged.

What should the voltage of an alternator be?

This time it should be at least 14.2 volts if the alternator is healthy and charging the battery. If voltage is good, turn on the headlights, interior lights, radio, heater and any other electrical load. The meter should still display above 13 volts.

What causes an alternator to make a squealing noise?

The serpentine belt could have stretched with age and may not be spinning the alternator pulley effectively, leading to a lack of charge. This typically results in a squealing noise. On the other hand, the internal bearings can wear out, causing a growl or grinding noise. 4. Electrical issues

Can a low battery cause an alternator to go bad?

This means that if your battery is too low, you will be unable to start the vehicle and thus you will also be unable to test the alternator, rendering any additional voltmeter-testing totally useless. If the weather is cold or your battery is old, your battery could be the issue and your alternator might be just fine.

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.

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.

Can you drive a car with a faulty alternator?

Faulty diodes can easily be replaced, but you will need to dismantle the alternator. It is impossible to drive the car with a faulty alternator. While it is the work of the battery to power the electrical components in the car, it cannot do this alone.

How to diagnose an alternator or electrical problem?