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Test Alternator and voltage regulator

'02 Camry,V6. Charging circuitry. Parts store pulled a code (Voltage reg bad. Where is the VR , what should aternator and VR be putting out. Thx

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Voltage regulators are inside the alternator now.. they are built in..operating voltage should be 14.5-16..depending on load requirements most tool shops have a battery tester that checks load and battery condition as well as charging of the alternator.. these go for about 25-50 bucks I use mine all the time..

Posted on Dec 27, 2013

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Posted on Jan 02, 2017

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SOURCE: 1979 Ford Thunderbird alternator not charging

Are the connections really dirty at the voltage regulator? These tend to get corrosion on them and cause weird charging system issues. Also make sure the ground is good on the regulator.

Posted on Jul 04, 2009

  • 958 Answers

SOURCE: Alternator or Voltage regulator

if you can carefully put a metal wrench on the rotating pulley of the alternator and felt a magnetism attracting the metal wrench, then your alternator is charging. if there is no magnetism, then the alternator is not charging...

another test is to measure the voltage on the small wires that went in to the alternator that says "F" for field, it should measure battery voltage...that is the voltage from the regulator..that means your regulator is working...but the altrntor is not..

without that battery voltage, then the regulator is he culprit...

pls be carefull...

hope i was able to solve ur problem..

pls rate me.. tnx, drcool..

Posted on Jul 26, 2008

  • 1779 Answers

SOURCE: Location of the Voltage Regulator

The source I checked says it's located under the hood, driver side, rear engine area on firewall (V-8 engines) Let me know how u make out.

Posted on Dec 18, 2008

  • 6826 Answers

SOURCE: overcharging alternator

This year it is not supposed to be in the computer,look on the firewall in the middle,I believe it is flat,and has a three wire connector,but only two wires in the plug,see if you can find it.

Posted on Feb 26, 2010

  • 373 Answers

SOURCE: 2000 Ram Van - is the voltage regulator located in the alternator

The voltage is regulated by the pcm (power control module ) on the truck. You cannot make any adjustments, removed or tampered with in any way to the pcm. Only a dodge dealer can check it out to see what the problem is with the pcm. Hope this will help you.

Posted on May 26, 2010

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Vehicles: any failing to keep its battery charged.

A vehicle unable to charge its own battery has one of 4 problems:
(a) alternator failure
(b) voltage regulator failure
(c) battery failure
(d) wiring problem between battery and alternator/voltage regulator.

One most modern vehicles (including 2002 Lexus RX300 - 2WD and AWD), the voltage regulator is an integral component of the alternator and is not separately serviceable.

In the US, one can get a free "charging system diagnosis" from the popular auto parts chains: AutoZone, Advance Auto Parts & Pep Boys. You needn't remove any parts from the car to get this diagnostic, since they can attach a diagnostic meter to the charging system in the parking lot. This diagnostic aid will tell you exactly which component has failed - battery, alternator or voltage regulator.

In case the vehicle is immobile, one can DIY (do it yourself) the diagnosis.
(a) inspect the wiring for corrosion/loose connections/loose connectors/etc.
(b) check alternator belt/pulley - if drive belt is properly turning the alternator pulley (no slippage/misrouting/etc.), then the mechanical tests are complete, and you'll need to continue testing the electrical performance of the charging system components.
(c) first component to test: battery
DIY test 1: remove battery from car and put battery on a 120VAC automotive battery charger and charge it fully (or just check it in the car with motor off, since the car's charging system is a type of automotive battery charger).
test parameter: a fully charged lead-acid automotive battery should read 12.45 volts on a VOM/DMM
DIY test 2: disassemble battery out of car after driving it to one of the auto parts chain stores (Advance/AutoZone/Pep Boys) for a free battery test. These testers will test the battery under load, which is not possible with just a DMM.
(d) if wiring is good, and battery tests good under load, then
the failed component is the alternator/voltage regulator - by process of elimination.
(e) DIY test 3: direct alternator/voltage regulator test (car must start and idle successfully to perform this test)
Start the car, and put a VOM/DMM across the terminals of the battery. Since the car is running, you'll be reading the output voltage of the alternator and not the output voltage of the battery. The acceptable ranges for alternator/voltage regulator output are:


Most alternators that are charging properly should produce a voltage of about 13.8 to 14.2 volts at idle with the lights and accessories off. Always refer to the vehicle manufacturer's specifications. Many Asian vehicles, for example, have higher charging voltages of around 15 volts.

When the engine is first started, the charging voltage should rise quickly to about two volts above base battery voltage, then taper off, leveling out at the specified voltage.

The exact charging voltage will vary according to the battery's state of charge, the load on the vehicle's electrical system, and temperature. The lower the temperature the higher the charging voltage, and the higher the temperature the lower the charging voltage. The "normal" charging voltage on a typical application might be 13.9 to 15.1 volts at 77 degrees F. But at 20 degrees F. below zero, the charging voltage might be 14.9 to 15.8 volts. On a hot engine on a hot day, the normal charging voltage might drop to 13.5 to 14.3 volts.

Here are the full specs for installation of the 2002 Lexus RX300 alternator - you may be able to check these specs yourself (with a torque wrench), or pass them along to your mechanic.

Note: the VIN 8th digit should be "F" for the 2002 Lexus RX300 (2WD & AWD)

2002 Lexus RX300 (2WD and AWD) - 3.0L Engine, VIN "F" SFI DOHC


Drive belt. Tension the belt to 170-180 lbs. for a new belt or 95-135 lbs. for a used belt.
Adjusting alternator lockbolt. Tighten the bolt to 13 ft.-lbs. (18 Nm).
Alternator pivot bolt. Tighten the bolt to 41 ft.-lbs. (56 Nm).

Glossary of acronyms
DIY = do it yourself
DMM = Digital Multimeter
DOHC = Dual Overhead Cam
SFI = Sequential Fuel Injection
VOM = Volt Ohmmeter

How to test a Car Alternator -

Alternator & Charging System Checks -

Dec 26, 2011 | 2002 Lexus RX 300

2 Answers

Alternator not charging

did you test the alternator? (it's a free test at most local parts stores).
Best regards,

Sep 09, 2011 | 1998 Toyota Corolla

1 Answer

My 2005 Pontiac Sunfire has had several problems over the past couple of months. When I was driving all my gages went to zero when I would start to break. After I started moving again they would go up....

Your car's symptoms (voltage fluctuations under load that shouldn't happen) seem to
strongly indicate that your voltage regulator has failed. The voltage regulator is the component
that regulates voltage coming from the alternator, and which is supplied to the rest of the car.
Your new belt tensioner indicates to me (and should have to your mechanic) that the
alternator and/or voltage regulator weren't able to operate properly, and a faulty belt tensioner
has killed more than one car's alternator/voltage regulator.
Your do not need new headlights. Do fix the turn signals.

In the 2005 Sunfire, the voltage regulator is an integral component of the alternator, and is
not separately serviceable. So your 2005 Sunfire needs a new alternator.

2005 Pontiac Sunfire Alternator - Duralast Part Number: DL2305-15-4 $199.99 available at:

The national parts chains (Advance Auto Parts, AutoZone, Pep Boys) will (for free) administer
a "Charging System Test." Which will telly you for sure that your alternator/voltage regulator
is bad. Do this before replacing alternator, since its a pricy part in the 05 Sunfire.

Just in case, Here's the 2005 Sunfire manual entry on (a) Diagnosis & testing the alternator, and
(b) replacement of the alternator

Alternator replacement is a do-it-yourself project, though you may need to get a
"Serpentine Belt Kit" on your favorite parts store's loan-a-tool program to remove/re-install the serpentine (drive) belt.
Diagnosis & Testing - 2005 Pontiac Sunfire Alternator

Alternator Load Test

1. With the engine running, turn on the blower motor and the high beams ( or other electrical accessories to place a load on the charging system).

2. Increase and hold engine speed to 2000 rpm.

3. Measure the voltage reading at the battery.

4. The voltage should increase at least 0.5 volts from the voltage test. If the voltage does not meet specifications, the charging system is malfunctioning.
Usually under and overcharging is caused by a defective alternator, or its related parts (voltage regulator), and replacement will fix the problem; however, faulty wiring and other problems can cause the charging system to malfunction. Many automotive parts stores have alternator bench testers available for use by customers. An alternator bench test is the most definitive way to determine the condition of your alternator.

Alternator No-Load Test

1. Connect a tachometer to the engine.
Ensure that the transmission is in Park and the emergency brake is set. Blocking a wheel is optional and an added safety measure.

2. Turn off all electrical loads (radio, blower motor, wipers, etc.)

3. Start the engine and increase engine speed to approximately 1500 rpm.

4. Measure the voltage reading at the battery with the engine holding a steady 1500 rpm. Voltage should have raised at least 0.5 volts, but no more than 2.5 volts.

5. If the voltage does not go up more than 0.5 volts, the alternator is not charging. If the voltage goes up more than 2.5 volts, the alternator is overcharging.
Usually under and overcharging is caused by a defective alternator, or its related parts (regulator), and replacement will fix the problem; however, faulty wiring and other problems can cause the charging system to malfunction. Many automotive parts stores have alternator bench testers available for use by customers. An alternator bench test is the most definitive way to determine the condition of your alternator.

6. If the voltage is within specifications, proceed to the next test.

Voltage Test

1. Make sure the engine is OFF , and turn the headlights on for 15-20 seconds to remove any surface charge from the battery.

2. Using a DVOM set to volts DC, probe across the battery terminals.

3. Measure the battery voltage.

4. Write down the voltage reading and proceed to the next test.

Removal & Installation - 2005 Pontiac Sunfire Alternator

2.2L (VIN 4) Engines

1. Before servicing the vehicle, refer to the precautions section.

2. Remove or disconnect the following:

Negative battery cable

Accessory drive belt

Alternator mounting bolts

Alternator electrical connectors


To install:

1. Before servicing the vehicle, refer to the precautions section.

Alternator. Torque the upper bolts to 37 ft. lbs. (50 Nm) and the lower bolt to 22 ft. lbs. (30 Nm).

Alternator electrical connectors

Accessory drive belt

Negative battery cable

2.2L (VIN F) Engines

1. Before servicing the vehicle, refer to the precautions section.

2. Remove or disconnect the following:

Negative battery cable

Accessory drive belt

Alternator mounting bolts

Alternator electrical connectors


To install:

1. Install or connect the following:

Alternator. Torque the bolts to 16 ft. lbs. (22 Nm).

Alternator electrical connectors

Accessory drive belt

Negative battery cable

Sep 05, 2011 | 2005 Pontiac Sunfire

1 Answer

This is not a car question. I have a boat (Ford Escort Diesel engine) that uses a separate voltage regulator. My alternator has not been charging properly and there is a 5 amp drain in my system that I...

You can take your voltage regulator and alternator off and take to most auto parts store and they can test them to be sure.

A 5 amp drain is significant if it is a constant drain. You might want to use an accurant clamp on amp meter to troubleshoot it. I assume you installed a fuse panel, so start by pulling all fuses, and then putting them in one at a time - write down your readings. The one that is highest is probably the line you need to troubleshoot.

But before you go through all that, do you have a refrigerator on your boat that is DC? If so, I would make sure that it is turned off before spending time troubleshooting.

Jul 01, 2011 | Ford Escort Cars & Trucks

2 Answers

My battery to my 84 chevy caprice is not charging. i got a new batery and altenator but it still wont charge.i have to jump it off to get it to start. i dont even know where the voltage regulator is...

the voltage regulator is built into the alternator,have you check the alternator connector for damage or corrosion check with a test light for voltage at the red wire that plugs into the alternator that is in the 2 wire plug connector as well as check the large red wire for voltage as this wire is the feed wire from the don`t say if this is a new or used alternator.if you have a voltmeter that is the best way to check for the proper amount of voltage at the test sites.the battery must have a minimum of 12.6 volts to start with higher is test the voltage regulator need the engine running and you need a voltmeter to tell properly if it is the back of the alternator their is a hole that looks like the letter D this is where you use something like a cotterpin and insert it into the hole you should feel a tab,push lightly on the tab and ground the cotterpin to the side of the alternator using the voltmeter you should see the voltage start to rise and hear it start to charge.the battery voltage and the feed wire at the alternator as well as the smaller red wire at the plug connector should be the same.charging voltage should be about 14.5 volts.

Mar 02, 2011 | 1984 Chevrolet Caprice

1 Answer

Charge light was on and alternator was overcharging. had alt. rebuilt and new voltage reguator, not charging now. only getting 2 to 3 volts are the charge fuse beside battery. new voltage reg is electronic...

There is a fuse under the dash that is the same one that operates the fuel gauge, if it blows the alternator wont charge. If the fuses are good I would take the alternator off and get it tested. Hopefully the rebuilder will warranty it. I would also make sure the new regulator is compatible with the old type regulator system. Most large auto parts stores can test alternators, and they normally do it free.

Dec 18, 2010 | 1984 Toyota Pickup Deluxe

1 Answer

Battery not charging

You'll need to either remove the alternator and take it to your local parts store to have it tested or, better yet, take the whole car to your local shop after charging the battery to have the charging system tested. I don't know if the voltage regulator is in the alternator or in the computer, but I suspect your voltage regulator is faulty. If the regulator is built into the alternator then you'll need to buy a new alternator / regulator assembly. If the regulator is in the computer then ( gulp ) you'll have to replace the computer. I hope it's in the alternator!! It is also possible you have a bad cell in the battery - in which case a new battery will solve the problem. Your parts store should be able to test the battery with a load tester to see if its ok. It would be easier to pull the battery first - but to save some time, I would pull the alternator too and have them both tested at the same time.
Good luck!

Nov 06, 2010 | 1995 Cadillac Seville

1 Answer

Instrument panel battery light, what indicates?

It indicates low or too much voltage. It's either a low battery, a voltage regulator that is going out (it's built into the alternator), or an alternator that is not charging the battery back up. If you know for a fact that the battery is good (not old and it holds a charge ok), pull the alternator and take it to a local auto parts store. Most of them will test it for free.

Jan 18, 2010 | 1991 Ford Bronco

1 Answer

The battery light came on when I was idling at a red light. Do you think I need a new battery? Camry 2003 80000 mi

when the battery light comes on, it doesnt Usually mean your battery is bad. it tends to be the charging system. take your car to your local auto parts store and have them run a diagnostic on the charging. they tend to do it for free, and it only takes a couple of minutes.
usually this will happen if your alternator is going out, or the voltage regulator. however, there is a possibility that your battery is not holding the charge anymore, but their test will tell you that as well

Jun 28, 2009 | 2003 Toyota Camry

2 Answers

Battery keeps going dead

1st clean the terminals
if that doesnt help try cleaning the battery (properly)
then try slow charging it
if none of these work id say get a new battery cosidering the ave. battery life is like 4-7 years

Mar 15, 2009 | 1997 Dodge Neon

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