How Do You Know if an Alternator Has a Faulty Voltage Regulator

Dan Ferrell writes about do-information technology-yourself car maintenance and repair. He has certifications in automation and command technology.

A automobile bombardment bleed tin can leave you lot stranded anywhere.

Photo courtesy of Longhair on Wikipedia

A parasitic battery bleed is when an abnormal and continuous belch of ability occurs after having close off the engine. Usually, this is caused by a curt circuit or an electrical device that remains in the "on" position or energized, such as:

• A trunk
• An under-hood or a glove-compartment light
• A switch
• A estimator module

Only a bombardment-power drain can also be the work of a bad alternator diode or even a faulty bombardment. Depending on the corporeality of current being tuckered, a parasitic draw will suck all the juice from your bombardment in a few hours or minutes.

Hither, yous have four tests to assistance you find the culprit:

1. The amperage battery drain test
2. The voltage drop battery drain test
3. The bad alternator diode test
4. The car bombardment hydrometer test

The first iii tests require the use of a digital multimeter. If you don't have one, you can purchase a useful multimeter for effectually 20 dollars. And you don't demand to have much experience in automobile repair to apply whatsoever of these tests.

Table of Contents

Hither are the sections you'll find in this guide. Skip to any particular office you are interested in or read about the tests in the society presented here (recommended) to follow a more systematic arroyo to your repair.

1. Preparing for the Test
2. The Amperage Battery Drain Test
3. Components Amperage Utilise
4. The Voltage Drop Battery Drain Test (alternative to the Amperage test)
5. Bad Alternator Diode Test
6. Car Battery Hydrometer Examination

1. Preparing for the Examination

Earlier you kickoff your tests:

• Plow off all accessories and remove the fundamental from the ignition switch.
• Unplug any device from the lighter socket, even if your device is turned off.
• Unscrew the light bulb from under the hood just enough to turn information technology off.
• If your vehicle has a fuse box under the dashboard—commuter'due south side—open up the commuter's door and use a clamp or similar tool to press and hold the door switch. Go out the door opened. The clench will keep the dome low-cal off during your test.
• If at that place's another fuse box on the passenger's side, follow the in a higher place procedure so that you have access to that fuse box during your tests likewise.
• To avoid defoliation, locate the fuses for your dash clock, stereo, and machine calculator, if necessary, so that you know that those circuits will show the presence of electric current during your tests. To know what circuit a fuse protects, look for the clarification on the fuse box lid, or look up the information on your vehicle service transmission.
• If you don't have one, you can buy an aftermarket repair manual for your particular auto model online or from one of your local auto-parts stores. Withal, your local public library may accept a copy of the manual in the reference section as well.
• The amperage battery drain test requires disconnecting one of the battery cables. If your car radio or alarm organization needs a lawmaking to reactivate it after cutting battery power, brand sure you know the code to turn information technology dorsum on.
• Use a computer memory saver to preserve computer and radio settings. You lot simply plug information technology into the cigar lighter outlet. On modernistic vehicles, it'southward recommended to use a retentivity saver that connects to the calculator's diagnostic link connector (DLC) like this Schumacher OBD-L retentivity saver detector.
• Finally, brand sure the car bombardment you're using for this test is fully charged.

The first test—the amperage battery drain examination—is best suited for older vehicle models, 1990s and older, that come equipped with i or two computer modules. With newer cars with more than control modules, usually you need to wait xxx minutes or so for the modules to turn off. And even and so, you may "awaken" one or more modules while conducting a battery drain exam. For this blazon of vehicle model—and older models as well if yous wish—apply the voltage drop battery drain test described in the next section.

One more affair. If your bombardment example is dirty or damp, thoroughly make clean the battery and platform it sits on, including terminals, if corroded. Utilize viii oz of water and ane table spoon of blistering soda as a cleaning solution. Dirt and acid may lead to bombardment drain.

At present, start your tests.

Notation: If you haven't used a digital multimeter before or have little feel using one, watch the adjacent video for some quick tips.

Measuring Amps With a Multimeter

2. The Amperage Battery Bleed Test

With the amperage examination, yous probe the unlike electrical circuits searching for the presence of electrical electric current when there should exist none.

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The best fashion to behave this test is to utilise an inductive ammeter capable of reading DC milliamps. That way you don't need to disconnect any bombardment cables; otherwise you can utilize the following method, but brand sure not to open any doors or activate any circuits once your meter is connected or you may destroy your ammeter. Also, endeavour to employ a memory saver to preserve your automobile'south computer and other electronic equipment settings.

• To brainstorm the amperage method test, disconnect the negative bombardment cable from the battery last. This is the black cable connected to the battery mail service with the negative (-) sign next to information technology. Then, connect your digital meter's ground (black) probe to the negative bombardment mail.
• Connect the meter's positive (ruby-red) probe to the battery cable terminal you just disconnected.
• Set your multimeter to the highest setting on the DC (direct current) amperage scale and turn it on.
• Now, check your meter'south display. It should read zero amps.
• Move the meter's dial to the adjacent lower setting on the amperage scale.
• Keep moving to a lower setting until you detect the presence of electric current. On a vehicle without a parasitic drain problem, this current is within a range of almost 50 milliamps (mA). On some modern vehicles, this upper limit might be much college. Consult your car possessor'south manual or vehicle repair manual. On a vehicle with a parasitic drain problem, this current will be higher than the normal range.
• On GM vehicles, divide your OEM battery's reserve capacity (RC) minutes by 4 to obtain the maximum describe. For instance, 120 (RC minutes) / 4 = 30 mA of allowable battery depict with the ignition switch off.

Preliminary Results

Reading inside range: If your reading is within range, yous're probably dealing with a faulty charging system or battery. To do a quick alternator drain power check using your digital multimeter, go to the section Bad Alternator Diode Test below. Then, if your alternator passes the examination, do a battery check using a hydrometer tool every bit described in the Auto Battery Hydrometer Test section.
Reading above range: A college amperage reading ways you lot have a problem in one or more of the electric circuits. Continue with the next steps and leave your multimeter continued to the battery. Use a pair of plastic clamps to concur the meter probes to the battery terminals, or ask an assistant for help.

Locating the Faulty Circuit:

• To locate the faulty circuit, beginning pulling out fuses, ane at a time, from each of your vehicle'due south fuse boxes, but leave the computer's and other module's fuses for terminal. Don't re-install any fuse back while conducting this test or you may "awake" a module.
• Begin with the nether-hood fuse box, if there's i. Pull i of the fuses and watch your meter'due south reading. Then re-install the fuse. Keep pulling fuses 1 at a time until you run across the unusual amperage reading on your meter get down to within normal range. When this happens, the excursion that fuse protects is faulty.
• Once you find the circuit causing the drain, check the clarification of the circuit nether the fuse box lid. It'll say something similar "Tail, parking, side marker lamps," "Radiator cooling fan," or "Blower motor thirty-amp fuse."
• Use your vehicle repair transmission to check the wiring diagram for that circuit. The diagram volition tell you lot what switches, loads, and connections are located in that particular circuit. These are potential problem points.
• Start with the switches, if whatsoever, to brand sure they are properly operating. If it is a door switch, for instance, brand certain the switch is still correctly mounted, and the door presses the switch off when closing.
• Brand sure the wires in the circuit are away from hot surfaces and connectors and loads have house and make clean connections.

Also, cheque for a loose wire—usually at a connector or load—or a wire with burned-out insulation causing a short excursion.

3. Components Amperage Apply

Knowing how much amperage dissimilar components use in your vehicle can give you an idea of the excursion causing the parasitic depict.

For example, if you find a parasitic draw of about .235 amps (235 mA), you may suspect a calorie-free bulb that is on all the time. A 1 amp depict may indicate an electrical problem with the radio, and and so on.

The following table gives yous a typical amperage utilize of different automobile components. Consult your motorcar repair transmission, if necessary.

These are just a few common electric components that may crusade trouble. There are many more than. If necessary, consult your vehicle repair manual.

Component	Current (14 5)
Fuel pump	5A
Headlights	15A
Radio	1A
Seat heater	14A
Heated rear window	9A
Alternator diode	4A
Interior lights	1A
Instrument console	2A
Number plate lights	1A
Brake lights	3A

A wiring diagram tin can aid locate potential trouble points on a circuit.

Photo courtesy of Leonard Yard. on Wikipedia

4. The Voltage-Drib Battery Drain Test

Although the amperage battery bleed examination has been a popular and reliable technique for some years, it is difficult to implement on many late model vehicles. Many of these models take several estimator modules that remain online for 30 minutes or more after you've shut off the engine and removed the cardinal from the ignition switch.

So y'all demand to wait for all these systems to go into sleep mode (standby) earlier you start your tests. And fifty-fifty then, you may accidentally "awaken" one or more modules while trying to observe the faulty excursion.

As well, if one of the modules is the i draining battery power, disconnecting the battery for the amperage test will turn the module off and prevent you from identifying the parasitic source, since the module volition reset.

With the driblet voltage test, you don't have to worry almost disturbing computer modules; information technology is a less invasive manner to locate a faulty circuit, and information technology works on older models only as well. Yet, you need a quality DMM (digital multimeter) for this test.

Before you brainstorm, though, brand sure you have a fully charged battery and that your meter probes have clean, pointy ends to reach the two modest test points on the back of each fuse; otherwise, y'all'll make inaccurate readings.

With this test, you'll check for the presence of voltage drop (lost voltage due to resistance in a excursion acquired by heat from electric current flow).

• To start, check your motorcar possessor'southward manual for the corporeality of time needed for the motorcar modules to shut off or enter standby mode (usually betwixt xxx and 60 minutes, or up to eight hours in some models). Too, check whether whatsoever of the control modules has an on/off cycle when the motorcar is just sitting, so that you lot read voltage drop on these modules during their off time period.
• After preparing your vehicle every bit described in the section Preparing for the Exam, set your digital multimeter to the millivolts (mV) scale and turn information technology on.
• First, examination for voltage drop on the fuses for the dashboard clock or stereo and computer's excursion, which take a small-scale electric current going through them. Bear on one examination signal on the back of the fuse with one of your meter'southward leads and the other fuse exam indicate with the other lead (do not remove any fuses), and watch your meter'south display. Since these circuits take some current, make a note of these readings and use them as reference.
• When ready, start with the fuses in the under-hood fuse box, if equipped. Then, exam the fuses nether the dashboard. Circuits with no current catamenia will read 0.0 mV of voltage drop. If you detect whatsoever amount of voltage drop, make a note of the amount, fuse amperage rating (for example 5, 10, 15A) and the excursion information technology protects.
• Catechumen whatever voltage drop reading into electric current period in amperage using these fuse charts.
• If the amperage exceeds the normal electric current draw for your vehicle, you've found the troubled circuit.

Preliminary Results

Fuse with voltage driblet: Look upwardly the wiring diagram for the excursion that the fuse with the voltage drop protects. The diagram is in your vehicle repair manual. Locate switches, connectors, or loads that may be activated or faulty. Also, look for potential brusque circuits—loose wires behind connectors or loads, or exposed wires making contact with metal surfaces.

No fuses with voltage drop: Yous may be dealing with a faulty charging system or battery. To do a quick alternator drain power check using your digital multimeter, go to the next section: Bad Alternator Diode Test. If your alternator passes the test, practise a battery check using a hydrometer tool. For this, go to the following section: Car Battery Hydrometer Test beneath.

Probing the fuses for voltage drop tin help you locate a faulty excursion.

Photo courtesy of havarhen on Wikipedia

5. Bad Alternator Diode Examination

Usually, a bad alternator diode volition crusade your headlights, instrument panel lights, or stereo display to flicker or dim and, sometimes, drain bombardment power overnight or much sooner.

A diode helps catechumen alternate current (AC) produced past the alternator into direct current (DC) past letting electricity travel in one direction—toward your battery and other electrical systems—and blocking current in the opposite direction—from your battery or other circuits to the alternator.

When ane or more diodes in the alternator rectifier fail, they volition prevent a continuous electrical supply to the electrical systems—dimming headlights, the radio display, dashboard lights, and other devices—and drain battery ability after the engine has stopped.

• To check for a possible bad alternator diode, switch your voltmeter to a low setting on the Air-conditioning (alternating electric current) voltage scale.
• With the engine running, touch on the meter probes to the battery terminals—positive (red) meter probe to the battery positive terminal, and negative (black) meter probe to the battery negative terminal.
• If yous detect more than 0.five ACV, it's likely the alternator's rectifier has ane or more bad diodes.

The presence of even a pocket-sized amount of Air-conditioning voltage volition indicate a bad diode, and then you'll need to replace the alternator's rectifier or the alternator.

half-dozen. Car Battery Hydrometer Test

The hydrometer examination is a quick manner to check the country of charge and health of your battery. It will let you know whether your bombardment is fully charged, needs a charge, or one or more cells have failed.

However, you can simply do this test on batteries with removable caps. If your car uses a free-maintenance battery (no caps), or one with caps, you can visit a local auto parts store and have them test your battery for free.

A hydrometer is an inexpensive tool. Buy one at your local car parts shop or online, and so check this article on troubleshooting a car battery using a hydrometer.

Basically, a reading below the 1.265 mark usually means your battery needs charging. A difference of 25 to 50 points between one or more cell readings ways your bombardment is lacking.

Testing for a Car Bombardment Drain

Car battery bug, particularly a parasitic battery drain, are difficult to diagnose sometimes. New vehicle models brand it specially difficult, time consuming, and frustrating. They come with more than control modules than previous twelvemonth models and hundreds more electrical circuits. But the amperage battery bleed test, voltage drib bombardment drain test, alternator diode test, and battery hydrometer test will assistance you chase down the culprit much more easily, whether you have a newer or older vehicle model.

This article is accurate and truthful to the best of the author'southward noesis. Content is for informational or amusement purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

Questions & Answers

Question: I put the negative tester lead on the negative battery last and the positive tester lead on the negative battery cable (disconnected from battery). I get zero milliamps, just get 12+ volts. I pulled each fuse one by one, no change. Connected negative cable and get a sizzling snap each fourth dimension. The motorcar won't first in iii to 4 days. It starts with a fresh accuse. What is happening?

Answer: At that place seems to be something connected directly to power (a curt somewhere) which is draining your battery and the engine won't outset until y'all become the bombardment to total ability. Remove the battery and connect your Ohmmeter between the negative and positive cables. If you get around 1 ohms, there's something shorted to ground. Check all engine grounds and look around for a loose wire, or a power wire touching the ground. Check the power battery cable from end to finish. Shorts are sometimes difficult to detect. Yous may try using a brusque finder.

Question: I want to bank check if both the alternator and bombardment are good, but they aren't showing any charge on the dash. What could be the trouble?

Answer: You can have your battery and alternator checked in one of the local car parts stores. If the accuse indicator on the dashboard withal doesn't respond, and then at that place'south a problem in the indicator circuit. The circuit itself is not complicated but may be hard to gain access to. You may demand the repair manual for your particular vehicle model to place wires and the best way to make it to the wires.

Question: How practice I check a JCASE box fuse using volt drop parasitic diagnostics?

Answer: You tin test each side of the fuse with the voltmeter. This video may help y'all:

https://www.youtube.com/watch?five=lRcj1fQcWwU

Question: I have a 1991 Ford E250. If I test betwixt the negative mail and the terminal, with everything shut off, my tester shows 4.v amp depict. If I pull the small wire off the alternator and examination over again, it shows 0 amps. It'southward a new alternator. I'm baffled. Do I have a bad alternator or is the draw somewhere else?

Respond: I've known this to happen with a bad voltage regulator. Have the alternator checked. Yous may want to try checking the excursion besides. This other mail may aid:

https://axleaddict.com/auto-repair/Charging-Organisation...

Question: Approximately how long does a parasitic bleed test take?

Reply: Information technology depends on how fast yous locate the circuit causing the draw and how attainable are the fuses to the circuits. You may be looking into 10 to twenty minutes including setting up.

Question: Is it possible for the tracking device to drain an iPhone's bombardment in 1 hr?

Answer: A tracking device may utilise up to 2mA in one day whether the engine is running or non. And so at that place should be some other source for power bleed.

Question: I have a 1983 Ford F-150. She was working fine and then, all of a sudden while on a long drive, her plough signals forepart and back, and brake lights, went out. Headlights nevertheless worked. Now we recently tried to start her and nothing. When trying to jump her, the cables became hot to the touch but nonetheless nix. I am going to follow this article in the morning; was just wondering if you had a good idea or had experienced it before?

Answer: The fact that the cables became hot is an indication of high resistance or possibly a short in the circuit. There could be damaged cables, corrosion or loose wires in the ignition system, multifunction switch, starting system. These other posts may assist yous bank check the circuits:

https://axleaddict.com/motorcar-repair/How-to-Utilize-Volt...

https://axleaddict.com/motorcar-repair/Automotive-Volt...

Brand sure engine grounds are clean and tight.

Question: I have a 1996 Chevy C1500. I replaced the tail lights and at present won't start. I put a new battery in it and it doesn't testify the alternator working at all. I changed the alternator for a new one but withal won't bear witness upward on the dash that its working at all. What could be the problem?

Answer: Y'all may accept a problem in the starting circuit. This two posts may help yous here:

https://axleaddict.com/motorcar-repair/Why-Is-My-Start...

https://axleaddict.com/auto-repair/My-Engine-Crank...

Question: Is information technology possible to examination for a parasitic current drain while my car battery is on trickle charger? My battery drains rapidly, its voltage level will driblet earlier I stop the testing.

Answer: It seems the battery is unable to hold the accuse. You may demand to test the battery first. You can do it yourself using a hydrometer. This other post may aid:

https://axleaddict.com/auto-repair/check-a-car-bat...

Question: I am reading 00.1mV on my brake lite switch/chmsl fuse. Is this enough to be considered the leak? All other fuses read 00.0

Answer: That's too small to be a leak.

© 2014 Dan Ferrell

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Source: https://axleaddict.com/auto-repair/car-batterydrain

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