Alternator dead short when power applied.
I have just installed a new 200 amp alternator with a Painless 10120 wire harness. When I check for continuity from the positive battery post terminal to the casing of the alternator or any area of the grounded engine block, I get continuity. So when I hook up the 12v. DC and try to install a 60/70 amp maxi-fuse of course it keeps blowing for I think I am creating a dead short. Is not the isolation post on the alternator where you hook up your 12v to keep the 12v from dead shorting. Why the continuity from positive post terminal to ground areas of motor and body of alternator. There is a
Experienced mechanics share their insights in answering this question :
Firstly, with the battery disconnected you will have continuity between the positive cable to the ground of the body or engine if you have any components hooked up or have fuses in. You are getting a complete circuit through some of these components. You will need to check to make sure all of the wiring on your power side is not touching ground before going through the components.
Disconnect the big main cable to the alternator and see if the short goes away. If it does, then use your meter to measure the ohms between the alternator post and the alternator case. You should have continuity in one direction and if you switch leads you’ll have no continuity. This will tell you the diodes are good or shorted in the alternator. If you have continuity in both directions then the large post is grounded or the internal diodes are bad.
If you can’t get it to work and you decide to get this fixed, consider contacting a certified mechanic who can diagnose your electrical issues firsthand and fix it accordingly.
How to Identify and Fix Common car Problems ?
Our sources include academic articles, blog posts, and personal essays from experienced mechanics :
It`s more than likely that your serpentine belt or one of the pulley`s is loose or worn out.
Another commonplace for electrical problems is in the alternator. If your alternator isn`t working correctly, it could cause a short circuit. You can test your alternator by checking the voltage at the battery. If it goes below 12 volts, your alternator may not be working correctly.
Technically, the role of the alternator is to turn alternating AC current from the engine into direct DC current for all your vehicle`s electronic devices. Over time, the diodes inside can short out and this can allow alternating current into your car`s electrical system, wreaking havoc on your car`s electronics!
A faulty alternator can lead to a weak or dead battery due to inadequate charging.
Symptoms of a burnt out diode:
The engine will begin to run rough, lack power and eventually stall and not start again. The battery warning light will turn on, warning you that there is a problem with your alternator charging system. The headlights will become dim due to reduced battery voltage.
Defective charging system – A car battery drains quickly if something called the alternator on your charging system fails to push out enough voltage, ideally between 13.5 – 14.5 volts. In this case, the battery will continue to drain even while the car is running.
It is possible that the drive belt has broken or come off the pulley, or the tensioner went bad completely. Alternators put out alternating current, and the battery needs direct current to charge, so there is a voltage rectifier that converts it, and it can suddenly go bad, too.
A dead or low battery can be caused by a failing alternator. It can also result from additional draw from auxiliary lights, fuses, sound systems, alarms and such.
An effective method to determine whether it`s your battery or alternator that`s gone bad is to connect jumper cables from a running vehicle`s battery to yours. After a few moments, try starting your vehicle. Once it`s started, remove the jumper cables — if your engine stalls, your alternator has probably gone bad.
Your car`s battery holds a charge, but the alternator works to recharge it while the vehicle is on. That`s why you can drive all day long without a problem but leaving the lights on overnight will drain the battery. If the alternator begins to fail, the battery will no longer recharge while the engine is running.
In the previous section, we assumed that the diode has an open-circuit failure. However, a failed diode can short out too. In this case, the diode will exhibit a small resistance in both directions. The common reasons for a diode failure are excessive forward current and a large reverse voltage.
Effects: The shorting of all of the diodes in the rotating rectifier assembly will in effect bias the main revolving field`s DC excitation voltage, and the generator`s terminal voltage will collapse.
The ignition relay is essentially an electrical device that works as a switch for the power to the ignition system. Its job is to make sure electricity flows from the battery to the different components that need power. A bad relay will drain your battery and make it difficult to start the ignition.
Intermittent Failures
In most cases, a set of sticking or worn alternator brushes, a broken field control wire, corroded battery cables or a bad connection at the alternator or battery will cause an intermittent low-state-of-charge problem.
No, the alternator provides voltage to the battery and other components. The PCM could possibly discharge a battery if it leaves a relay or another circuit on, but most likely is is not the cause of your alternator failure.
Every alternator works under load while generating electricity. Because of the substantial load handled by the alternator, the rectifier diodes fail because of overheating, overloading or because of poor connection between the alternator output and the battery positive terminal.
Set your multimeter to DCV (DC Volts) above 15. Make sure your alternator`s positive and negative terminals are clean. Put the multimeter`s black cable to the negative terminal and the red cable to the positive terminal. Look for an ideal alternator reading of around 12.6.
If the engine starts but dies immediately, your alternator probably isn`t keeping your battery charged. If a jump starts and keeps your car running, but the car can`t start again off of its own power, a dead battery is probably your answer.
To do a short circuit test first of set the value of field current at 0 and connect the output terminals of the generator by the ammeter. After that find the value of the armature current (IA) by changing the field current.
There are three key wires in the loop: a positive wire for the battery, a sensing wire for voltage, and an igniting wire. The ignition input wire is linked to the engine. The energy detection cable monitors voltage and transmits it to the converter, while the energy wire links the alternator and the engine.
If your alternator fails when you`re far from home, you can typically drive up to 200 miles on battery power alone. That`s assuming your battery is in good shape and fully charged. Of course, it`s best to get the alternator repaired or replaced as soon as you can.
Since the current can only flow in one direction (forward-bias), we unofficially think of diodes as one-way electronic valves. If the voltage across a diode is negative, then no current will flow; thus, an ideal diode appears as an open circuit.
The breakdown of a diode happens when you apply a reverse bias across the diode. There are two types of breakdowns in p-n junctions, which are Avalanche and Zener breakdowns. When a diode is designed for a specific breakdown voltage, it is called a breakdown diode.
Relevant Questions and Answers :
the most relevant questions and answers related to your specific issue
Alternator dead short when power applied.
ANSWER : Firstly, with the battery disconnected you will have continuity between the positive cable to the ground of the body or engine if you have any components hooked up or have fuses in. You are getting a complete circuit through some of these components. You will need to check to make sure all of the wiring on your power side is not touching ground before going through the components.
Disconnect the big main cable to the alternator and see if the short goes away. If it does, then use your meter to measure the ohms between the alternator post and the alternator case. You should have continuity in one direction and if you switch leads you’ll have no continuity. This will tell you the diodes are good or shorted in the alternator. If you have continuity in both directions then the large post is grounded or the internal diodes are bad.
If you can’t get it to work and you decide to get this fixed, consider contacting a certified mechanic who can diagnose your electrical issues firsthand and fix it accordingly.
Read Full Q/A … : Alternator dead short when power applied.
My car will not start. It is completely dead (zero power), is it my alternator?
ANSWER : A failed alternator is a possibility, and is among the components that would be checked first, but it is not the only possibility. Charging system output should be verified against factory specifications. To have the alternator inspected and replaced, if necessary, please request an alternator inspection/replacement and the responding certified mechanic from YourMechanic will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.
Read Full Q/A … : Alternator dead short when power applied.
There’s no power to the whole fuse area.. including the horn and car won’t start.battery is good.could this be a dead alternator?
ANSWER : Hi There,
I would start by checking the connections to the battery to be sure the cables all have proper connection to the battery as well as the ground. Additionally, check the power to the fuse box to determine where the last place the battery directed power to was. If you need additional help with this, please reach out to us here at YourMechanic to schedule an appointment to have a professional come to your location to diagnose and repair your electrical problem.
I would start by checking the connections to the battery to be sure the cables all have proper connection to the battery as well as the ground. Additionally, check the power to the fuse box to determine where the last place the battery directed power to was. If you need additional help with this, please reach out to us here at YourMechanic to schedule an appointment to have a professional come to your location to diagnose and repair your electrical problem.
Read Full Q/A … : Alternator dead short when power applied.
I got a new alternator, radiator and battery after the installation my ground wires had a short from my battery. 0 power to right
ANSWER : No lights means the circuit is dead and that could be due to a fuse, fusible link, relay or other in circuit component that somehow got damaged by the short circuit. It sounds like several circuits are affected. The thing to do therefore is simply trace (from the power source) one of the simpler circuits to find the cause of the open, on the theory that a common, perhaps large fuse, controls all of the failed circuits. If not, each circuit that is non functional will have to be tested in turn til all are restored. You will need the factory wiring diagram to make sense of each circuit and determine at what points to test. If you want these steps performed by a certified Mechanic, dispatched by YourMechanic right to your location, please request a circuit(s) diagnostic/tracing and the responding certified mechanic will get this taken care of for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.
Read Full Q/A … : Alternator dead short when power applied.
Can a bad alternator cause the car to jerk loose power
ANSWER : Hello, thanks for writing in about your 2000 Ford Escort. It does sound like the alternator is not charging but this would need to be tested to make sure it is in face the alternator at fault and not wiring or another issues. If you need assistance with this, consider YourMechanic, as one of our mobile technicians can diagnose your loss of power firsthand for an accurate repair.
Read Full Q/A … : Alternator dead short when power applied.
No power past Starter Solenoid
ANSWER : Hey there. That is a tough one. If your not getting power past the solenoid, the only thing I would consider is that the ground connection from the starter is faulty or the wire itself is frayed. On an older Dodge like your W100, I would suspect electrical wires and connections as being the trouble spots. Check all connections and replace the ground wires to be on the safe side to see if this resolves your issues.
Read Full Q/A … : Alternator dead short when power applied.
How much oil needs to leak into an Alternator to cause the Alternator to go bad
ANSWER : It would be difficult to say exactly how much oil it would take to cause the alternator to fail. However, oil leaking on the alternator due to leaking valve cover gaskets can cause it to fail. It seems as if the technician who is servicing your vehicle may not have performed a courtesy inspection to check for other potential issues prior to starting the other repairs you had requested. I would recommend having the alternator replaced if it has oil leaking on it as well as resolving the valve cover gasket leak to prevent it from happening again. You may try to use a different mechanic who is more upfront and honest in the first place. Consider YourMechanic as services such as this can be completed from your home or office.
Read Full Q/A … : Alternator dead short when power applied.
My car died while on the freeway and I lost all power to my headlights, taillights, blinkers, power steering, windows and door loc
ANSWER : Hi there. Power to operate your vehicle during operation is supplied by the alternator. If you lost power to all systems, it will be caused by either the alternator failing, or an electrical relay or connection being damaged. Circuit tests should be performed to prove the failure(s). It could be that the fusible link(s) have burned near the battery positive cable. If the fusible link(s) have burned, the short that caused the failure needs to be identified. It could be a faulty ignition switch is the source of your issues as well. It would be a good idea to have a professional mechanic come to your location and complete an electrical components inspection so they can determine what is causing your problems.
Read Full Q/A … : Alternator dead short when power applied.
