It started whining one day, so the next day I took it to my mechanic. A bad diode will show up on the meter. Has anyone had their late model Altima alternator changed? Identify the underlying cause of the whine to silence it for good. Yes the diodes are pressed in, and they are not that hard to replace. This is causing the whine. There are several possible causes of alternator whine and troubleshooting is the best way to isolate it. This also causes a drop in the amount of charging current the alternator can deliver to the battery so the system is degraded. Customer : It is an electrical whine, not a bearing noise. A bad diode in the alternator will cause noise. Two test methods can be used to test the alternator without disassembly. It's usually caused by a ground connection that is less than ideal. The main alternator components are the rotor and stator, along with the diode and the alternator pulley. The alternator is quiet when started in the morning but the whine becomes noticeable as soon as the headlights are turned on. Jan 29, 2017 at 3:52 PM #36 #36. joeguam New Member. Electronics have ZERO protection from AC ripple. These meters were originally sold as the Ward Aero I took it apart and did some testing and determined the rectifier was bad. As the RPMs of your vehicle rise, the volume of the alternator whine can increase as well. It has 4 holes in this plug with one of them bigger than the other 3. A--If the whining sound you describe has a high pitch, it might be a bad alternator diode. This will cause loud alternator whine especially when the alternator is called on to put out a lot of amperage. tims auto repair : After you start the car, even if nothing is on, the alternator will be under a load until the battery is fully charged from starting. If a diode in the alternator goes bad it causes a higher ripple wave in the charging current. A bad diode will show up on the meter. Customer : If enough diodes fail it will cause various minor problems and you will have a weak battery. Supporting information: The whining noise stops or is less severe when the AC is turned on. Causes of Failure Diode overheating also occurs when the alternator is used to bring an undercharged battery up to a fully charged condition. The vehicle electrical system relies on … Problem: whining noise coming from a bearing in either the alternator, compressor, pulley (according to a mechanic, but he can’t tell at the moment). The alternator generates this AC signal as a by-product of how it works. The old battery will work fine in an '86 or older car with the better generator. 2008 Honda Odyssey alternator whine - diode? GM alternators develop a 'whine' or 'whistle' noise that follows the engine RPM. Alternator whine is caused by a small amount of AC signal component on your DC power supply to the radio. Then it became more frequent and soon was happening all the time. GM alternators are 3 phase with two diodes for each phase. If a vehicle is parked for an extended time, it can cause the alternator bearings to bind or seize. There are six diodes in an alternator pack. A related issue to alternator whine, is RFI generated by the diodes themselves. Some automotive electrical shops will rebuild the alternator and replace the diode bridge. Alternator bearings take time to wear out, and typically you will get plenty of warning signs. Many modern vehicles produce some whine on modern FM rigs. One day as I pulled into the parking lot for a dentist appointment, the whine suddenly increased in volume. Another problem altogether, which is often incorrectly identified as alternator whine, is the switching transients from the alternator's regulator. If a diode has failed or there is a bad winding in one of the phases there will be a gap in what should be a smooth production of current and the windings will whine. Since it is radiated RF energy, removing the antenna will cause it to go away. A choke and capacitor that filter out the noise riding that line. But an alternator has three phases, each separated by 120 degrees, and due to the Star configuration, two phases work in series at any given time. To understand what the common alternator problems are, we should first know how it actually works. If an alternator diode fails, the amount of ripple voltage increases markedly. It started making an always present but throttle sensitive whine. This does indicate the alternator *may* be the cause. Basically any component that touches the low level music signal (from RCA cables). Alternator whine is nearly always the product of the rectifier (faulty diode) not clipping the entire AC wave to convert it into DC. Mar 02 2011, 8:20pm. No light in dash ever. Re: alternator whine. 2008 Honda Odyssey alternator whine - diode? As the vehicle is driven to bring an undercharged battery up to the correct voltage, the excessive current flow can overheat the diodes, leading to failure. But, when diodes start failing, your saw-toothed DC output becomes more AC, which … It will appear louder at low rpms, and when there is a high amperage load. It gets higher pitched as the RPM's increase. Identify the underlying cause of the whine to silence it for good. There are several possible causes of alternator whine and troubleshooting is the best way to isolate it. If proper grounding and wire placement does not eliminate the noise, a filter may be the ultimate resolution. If proper grounding and wire placement does not eliminate the noise, a filter may be the … The excessive whine in the speakers suggests your generator already has a defective diode. You still want to get the alternator replaced, as it will fail completely in the near future. Alternator whine is almost always caused by a ground loop. I replaced that and, while dissambled, also replaced the diode trio, brushes, and bearings. After 198K miles of flawless service I replaced the OEM alternator with a Bosch rebuilt unit. I know there is a problem with it whining and a friend of mine who is a service advisor for Nissan told me they are changing them under warranty at Nissan. The whine or hum happens because the alternator, a three-phase device, is “out of phase”. A diode pack on the alternator converts AC current from it's windings into DC to charge the battery. An AC wave impressed in a DC system can destroy your avionics and should not be taken lightly. Well, under load the electromagnets pull on the ohmeter putting pressure on the bearing. If the belt loosens or breaks, your alternator won't be able to send power to your battery anymore. Alternator Whine 03-21-2021, 04:42 PM. Using a good quality digital multimeter on the bus to detect AC is highly suggested. Put simply, the alternator converts the mechanical energy from the engine into electrical power for the car’s accessories.The way alternator’s … A high pitched noise that raises and lowers with the rpm of the engine. Alternator whine can be a symptom of a bad alternator diode. Sometimes the whning noise in the alternator is caused by a bad diode in the alternator. It’s a question of time before the alternator goes out. Some automotive electrical shops will rebuild the alternator and replace the diode bridge. Jan 25, 2017. 09 Challenger SRT8 (gone), 10 Jeep GC SRT8 11 GMC Sierra Ext Cab LB. You can have failing diodes that cause noise but the alternator will still work. The best fix is usually an external filter that goes in the DC power line to the radio. The diodes in an automobile's alternator serve the same function as a one-way check valve does in a hydraulic system. You have a bad diode(s) as the tests say. Troubleshooting … Now 25K later the alternator has developed a noticeable whine: the pitch is proportionate to engine speed and the loudness is proportionate to the amount of current output. Joined: Oct 2, 2016 Member: #4744 Messages: 237 Gender: Male First Name: JOE Vehicle: 2015 Toyota Tundra SR5 Pro Comp 6 Inch Stage II Lift Kit with Icon 2.5 coil overs and piggyback rear shocks, SPC Upper Control … Your alternator is attached to a pulley system (or wheel) that has a belt on it, known as an alternator belt (go figure, right?). - YouTube. Word of the wise, if you're in need of an alternator, steer clear from an Auto... Change after change after change, finally resolved my noise problem on my EM2. I had the same problem with a 1993 Oldsmobile 88. After cleaning the battery terminals and retightening the cables, I realised the diode whine sound had gone. Alternator whine in your car stereo can be an elusive problem. You almost never have the issue with late-model stock alternators, but it seems to be the norm with cheaply-(re)built, aftermarket alternators. It sounds a lot like ignition and/or injector RFI, so it is difficult to diagnose correctly. At first it seemed to come and go. Shorted diodes can cause AC to ride on the DC. Does your whine sound like this? What I have learned is that after doing various checks on the Alternator there is no reason I should hear diode whine. The only fix is to … To me, alternator whine is the most annoying form of noise. Failing diodes or a bad stator will normally generate a whine in the headset that will vary in pitch with the R.P.M. I suspect that one of the diodes associated with a particular phase has failed while the other 2 phases are charging properly. Under heavy electrical load the alternator cannot keep up with demand so that is the reason the voltage warning light illuminated briefly. The main culprits are the amp, the head unit and any intermediate components such as crossovers and equalizers. How does an alternator actually work. An alternator is a three phase device. If playback doesn't begin shortly, try restarting your device. Also you are correct, the while running voltage it too low. It’s a question of time before the alternator goes out. Two test methods can be used to test the alternator withoutdisassembly. I was parked for about an hour, … But does not address if the noise is caused by a failed diode pack(s), or simply from induction / amplification. I see the 3 stator wire outputs only go through one diode for each phase. Secondly, this alternator has 4 posts in the back, as well as a 4 pin connector. In the schematic, N,F,E are on the connector. B is the output post. Alternator whine is caused by a difference in electrical potential (voltage) between two points. Sometimes it appears as a low level audio on the TX side, sometimes very bad, sometimes just barely noticeable. Sometimes it's noticed on the RX side, even when the radio is squelched. This alternator on a Toyota, came in with the owner complaining of a whine under the hood. Check out this video. As you mentioned prior, the whine / noise flutuates as the RPM's increase. 69 Ponitiac GP 428. When the RMPs increase, such as when you accelerate, you’ll hear the noise get higher in pitch as the pulley spins faster. If one of the negative diodes fails and shorts, internally, the alternator usually whines and gets hot, when it runs, as well as doesn't charge very well. Vizsla, Jan 29, 2017 #35. A bad diode in an alternator can whine. Shorted diodes can discharge a battery in a short period of time, and cause the alternator to whine or hum at idle or low speed. You can't charge a direct current (DC) system using alternative current (AC). of the engine. The following steps will aid you in locating and correcting a ground loop problem. There is a hand held unit with a probe that clamps over the alternatoroutput wire. The 11.7 volts you stated does not indicate it is charging correctly. There is a hand held unit with a probe that clamps over the alternator output wire. If you unplug the connector and the whine stops then it's bad diodes. Diodes allow electrical current to flow in one direction only, and are the essential part that converts alternating current (A/C) to direct current (D/C). While diode induced whine directly varies with engine speed, regulator whine normally does not. 15 Hellcat incoming - someday - Finally picked up 10/10/15 - Wow! An alternator is a 3 phase device. I had convinced myself that the noise was coming from the power steering pump, but I was wrong. When diodes go bad in an alternator the alternator will "whine." Alternator whine can be a symptom of a bad alternatordiode. I tried the alternator unplug test and that does indeed make the noise go away when plug is out and noise comes back when plug is in so it's definitely the alternator. Alternator Whining Noise A common sound made by failing alternators is a very high pitched whining noise that you’ll hear when the engine is running. Sometimes the whning noise in the alternator is caused by a bad diode in the alternator. Common symptoms that the alternator bearings are wearing include a squealing sound that may get louder as the engine RPMs are increased. That this is the problem is confirmed by the poor output under full load. For those of you who are lucky enough never to have been exposed to alternator whine, it sounds like a miniature siren that rises in pitch with the speed of the engine. So for each pair of windings in series there are four diodes in operation, so this is indeed a full wave rectifier. anyone know where I can buy this one wire connector plug for the alternator? A bad diode in the alternator will cause noise. The 11.7 volts you stated does not indicate it is charging correctly. anyone know where I can buy this one wire connector plug for the alternator? Diodes in an alternator take the alternating voltage and "bridge-rectify" the alternating voltage into a saw-tooth voltage that never goes negative (alternating goes positive/negative/positive/negative...). I see online people say this is likely bad diodes. I would get it fixed. It's rare, but I've also seen a pulley break or become bent. I had the alternator diode whine for several months. I replaced idler and tensioner pulley which did quiet down some noise but that didn't get rid of the high pitch whine noise. The battery "smooths" out the pulses of energy from the alternator. That ripple will also cause a whine … I'm running a Delco 12si alternator converted to 6v pos grd by Larry Becker about 10 years ago. That will reduce the output capacity to one third of the unit's rating, and "ripple" will be very high.
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