How to test Alternator with & without Multimeter (Peterbilt Paccar Semi truck)

Рет қаралды 35,284

DIY Repair

Күн бұрын

Easy way to check alternator on any engine with the help of a multimeter

Пікірлер: 12

@glenmaise8184 3 ай бұрын

Does not mean that that alternator is charging the battery that means that that alternator is charging you have to test at the batteries test at the batteries while running to see if it is charging the batteries😊😊😊

@letitrest4662 2 жыл бұрын

Your test isn't necessarily accurate. The alternator needs to be tested under full load, with all the lights on, the air conditioning running on high fan speed, wipers running and so on. THEN, if you're getting 13.5 to 14.2 volts, the alternator is likely okay. THE REASON ; Without a load on the alternator, you can have one or more bad diodes in your alternator, and it will show that it's charging normally. Same thing with the windings. one or more of the copper windings can go bad. I used to rebuild alternators. If the windings, and there's three separate ones, all together, have gone bad, usually you'll see that at their terminal ends. The copper becomes crystallized. One or more bad diodes, discharge the vehicle battery when the vehicle is not running. It's a very low power draw, and depending on how often the vehicle is driven, and the load on the charging system, it may just appear that your, once new battery, only lasted a year. This is why the only accurate way to test an alternator is under full load. A carbon pile bench tester is the best device to use, because it actually can put a full load on the alternator. The person doing the test runs the alternator on the bench tester, and slowly increases the carbon pile, while watching the amperage draw. So if you have an alternator that's rated at 140 amps, this test allows a full 140 amp power draw. If the alternator is good, then at rated amperage, in this case 140 amps, the voltage is at least 13.5 volts, and hopefully 14.2 volts. If not there's a problem. It could be one bad diode. There's six diodes in an alternator. Two for each winding. Since the alternator stator and rotor actually produce alternating current, the alternator has an assembly within, called the rectifier. The rectifier is made up of those six diodes, built into a heat sink assembly that cools the diodes. What diodes do, and what they do in the alternator..... The diodes only allow current to flow in one direction. I told you there's six diodes. Technically there's three positive diodes and three negative diodes. Together they take the alternating current that's being produced in the windings, and turn that alternating current into a direct positive current, to charge the battery. If a diode goes bad, it will allow current to flow in either direction, or maybe no current flow at all. When you have one or more bad diodes, that diode is allowing current to be drawn out of the battery, while the vehicle isn't running. Scenario ; You just got a brand new battery, and drive your vehicle to the airport, where it's going to sit for a week, while you're on vacation. You get back to the airport after flying home, load your suitcase into the trunk, get into the car, expecting your new battery to fire up the vehicle. Instead your battery is dead as a door nail. That's a common scenario with the alternator having one or more bad diodes.

@sandhu22gg 2 жыл бұрын

Thanks for the information 👍

@rooseveltrainesjr7618 Жыл бұрын

The test wasn't helpful. I new something was wrong when my 2018 cascadia. When I here my inverter going off. But not just the inverter I new something was wrong when my volts on Mt gage was reading 12.5 or 12.6. I opened my hood an. Use my volts meter at the alternator. But my engine was running an I check the alternator 12.5. It should be reading 14.2. An did the same thing on batteries. 12.5. Bad alternator. I have a apu. On my truck so I will lett it run. Heading to the house to fix my alternator myself. Guys get u a volts metter

@geoestrada5001 2 жыл бұрын

I believe The alternator last only 5 years depends on how much of work you been driving and battery last 2 years of life but as soon you replaced alternator you should replace the starter too, thanks again brother

@RiyazAhmad-rz8oy 2 жыл бұрын

Same thing u can test on battery terminals wt u take risk on start engine

@rollguy341 2 жыл бұрын

Gonna add a negative cable to the alt, like in your video. Best method to ensure a better ground and never seen it on any others but I am running high in volts, well battery needs replacing now as it is bad high voltage. Still runs car though. Anyways, thanks, as I am super grounding my car (aka cleaning posts to ensure grounding). Just stuck on why still high volts to battery until I get new one. Hard answer to find on an 18 volt charge issue even with a new alt.

@glenmaise8184 3 ай бұрын

Sir your alternator is new I understand but it is a bad new alternator bad new alternator