How to Test an Alternator Without a Multimeter (Old School Alternator Test)

By using this information user assumes all risk of use.

[manikmek]

Touch a piece of steel (screwdriver) to the alternator rear bearing or if not accessible carefully touch to the rotating pulley on the front of the alternator with the engine running. It becomes magnetized and the metal will stick to it if it is working. Try it again with the engine off to notice the difference. If the metal sticks without engine running. The diodes are fried internally. Replace it.

[henrykemka]

Thank you so very much for this DIY alternator test. Very kind of you to share your mechanical nous.

[jmsskpq]

Why fucking thank you sir saved me alot of arguing tonight

[Foxxie]

Very good advice to NOT ever touch the positive back when it's running or it could blow the computer stuff.. I know I did that with a guys truck some years ago.. He thought his Alternator was bad, and I told I could show him how to check.. I took it off and the truck keep running, then I put the positive back, and killed the truck instantly.. Luckily, a mechanic had a used device laying under the counter, that he gave to the guy free of charge..

[GlorifyGod]

This information is extremely helpful. 👍 👍

[JasonTatunay-pl]

Thats an old school way of checking if ur alternator is charging helps alot👌

[robertfitzkee]

You can disconnect the battery while the car is running it won't damage anything. We're did you people go to automotive school at that told you this. They suck for schooling. But this trick only works on older vehicles but t anything over 2000 it won't work for because of the design with the computer it's design to shut the vehicle off wants the battery is disconnected. I've been a mechanic since 93 and came from one of the top schools where nascar mechanics come from and can pretty much fix anything on a car or race car. There and s no harm with disconnecting the battery while the car is running just don't let the terminal touch anything or you could have issues then.

[michaelvarble]

Another way on the older vehicles you would feed the field side of the regulator if it charged it was the regulator if not it was the alternator. On generator type systems you would ground the field side of it charged it was the regulator and if it didn't charge it was the generator. On some of the 50s cars the power steering pump was on the output end of the generator shaft that drove the pump. On older Chrysler vehicles that had a small black box regulator you could remove the cover and turn the field screw in to achieve a higher voltage on those people that drove short trips with the A/C on because the compressor took 5 HP to operate and lots of voltage. So we would crank those up to 14.9 volts to maintain battery voltage

[ednasanchez]

This trick works perfectly fine on my Bronco II 1986

[mike]

As an aside:
Yes your method is useful on pre computer vehicles.
On a vehicle that’s not charging that is equipped with a stand alone voltage regulator if you use your method and if it stalls when you pull the cable, it’s the alternator if it stays running it’s the regulator.
An old mechanic taught me that 50 years ago.

[DavidJones-qxyf]

I tested with a multimeter and it shows the battery charging with engine running at 14.2+ volts yet I do this trick and the engine shuts off immediately . So now I'm more confused than before !!

[jamesperkins]

This could possibly damage the computer if you have electronic ignition, although I did on older models with the distributor and points.

[ZingPow]

Nothing will happen to your computer to those who are posting it will 😂 You will only delete settings like your stereo pre settings and for those with power seats your pre settings so this method is fine

[albertwoods]

Thanks, good fast video.Keep up the good work

[jameswhite]

I just did it on the positive side and car runs why are people staying that to remove the negative cable, I have a 2010 Toyota Corolla thanks for posting

[MrAvant]

I dont advise this TBH. In some alternators this can spike the voltage regulator or even worse some of the cars management modules....

[GRBHERBTPUSY]

Thank you! I dont have to rebuild my alternator..

[dini]

Tried this engine cut out…looked at the alternator and realised the belt fell off must be a bad tensioner

[louisostlie]

ITS ONE OF THE BETTER PRATICESS TO NOT REMOVE THE BATTERY, IT ACTS LIKE A CAPACITOR TO THE ALTANATOR

[pedrotalavera]

I cannot believe this is still done and recommended today. If you want to save money and listen to this advice you could actually be spending a lot. This can cause a spike of voltage and damage the alternator and computers in your car. Do not do it. At least use a voltmeter. But to test an alternator properly you will need other tools.