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Sun Mar 31, 2019 12:24 pm

I 've gone thru all the alternator threads (I think) and want to know what type of light to hook up with a battery to test alternator while on the bench? Any 12v light ok or does it need one of particular resistance value? I have a spare speedo I could hook it up to if need to be but it'd be much easier if I could just use my test light. Thanks

Sun Mar 31, 2019 12:51 pm

I did it, I used a 12 Volt Incandescent head lamp for the load and a bunch of flashlight batteries for the excitation, you will need around 6 volts excitation. I found a combination of sockets to fit my drill motor to spin it. Mine would load the lithium Ion powered drill motor down before producing a full 12 volts with the headlight as the load but if it works at all it's probably good.
With a 12 volt car battery for excitation, I would think a 12 Volt Brake Lamp bulb in series would work. Also the 6 volt setting on a battery charger would work too.

Sun Mar 31, 2019 1:10 pm

Is that headlight for a load? Wouldn't a meter work as well? Looks like you got meter probe hooked up there. I was referring to test light to mimic light in speedo that needs to function for alternator to work. I might add my alternator is internally regulated. I got 12v car battery to wire in series with test light and meter testing for output voltage. I'm I missing something on bench testing?

Sun Mar 31, 2019 6:25 pm

Just hook it up as it would be in the car. Positive 12v to the threaded battery terminal, negative ground from the 12v source to the body of the alternator. Then hook one side of an incandescent light/clip of your test light to the positive of your 12v source. And the other side of the light/probe of the test light to the spade terminal on top. The light should light up when hooked up, and should go out upon spinning up the alternator. Word of caution, when the alternator starts producing current, it puts a fairly large load on it. It needs to be fastened WELL to your testing stand, and it may very well torque the drill out of your hand. You can simply measure the voltage at your 12v source for charge output.

Sun Mar 31, 2019 9:31 pm

Most Napa stores will test it for free.

Sun Mar 31, 2019 9:53 pm

Meters and test lights are higher ohms than needed. That's way the head light is being used for the B+ load and the brake light for the 12 volt batteries current limit to the D+.

If you wire it just like it is in the car then the battery would be a load and you could use a meter to read the B+ voltage but your going to need more than a portable drill motor to turn it enough to see the voltage across the battery rise That's why I did not connect a 12 volt battery.

Sat Apr 06, 2019 1:13 pm

Your goal in bench testing a alternator is to find out that it puts out over 13.5 volts. Low rpm on it using a drill method will light a bulb at 12v but if it dosen't climb to around 13.5 volts the voltage regulator is not functioning and will never charge the battery properly. If its suspect, change the internal voltage regular its easy and only cost around 25.00 The dill method dosen't spin the alternator fast enough to produce the voltage your looking for.

Sat Apr 06, 2019 1:23 pm

You guys need to throw away your 3/8 battery powered Harbor Freight drills, and get one with some balls.... I had no problem getting 13.5+ volts with a 110v 1/2 Milwaukee.

Mon Apr 08, 2019 3:10 pm

For use with type 1 generators and alternators, a standard gen stand bolts where the type 4 alternator adapter is now.

Note: I will be putting a bigger pulley on the (1 hp) motor to get the speed up. For a load I use a harbor freight 500 amp carbon pile tested ($50), adjusted down to 55 amps.

Fri Sep 27, 2019 9:36 am

It's a play thing wrote: Most Napa stores will test it for free.

Dude!
Just looked at your photos.
That Thing is bad ass.
Love the Chenowth Fast Attack too.

Makes me wish I lived somewhere else.
The only off-road options around here are for mountain biking.

Fri Sep 27, 2019 9:53 am

It's a play thing wrote: Most Napa stores will test it for free.

Oriely's as well

Autozone wont. Too dangerous for their employees :lol:

Fri Sep 27, 2019 10:14 am

Just added an idiot light to my engine test stand. Got a flanged socket and a generic side marker bulb. One side wired to 12V, the other to the proper terminal on the alternator or regulator. Works fine. I have an old hack switch light somewhere that I just used aligator clips and a switch, but I think its on the one project car.

Fri Sep 27, 2019 10:24 am

All of the above testing might prove the alternator "works", but none of them will prove it works correctly. Just because it puts out 13.5v (or whatever number you pick) does not mean it's a good alternator. To do that you need to load it to its rated amperage output with a carbon pile load tester (or similar method that can load it to 50A or whatever it's rated at). Loading with a headlight bulb is a joke- most headlights only pull a couple of amps. If you have a blown diode in the alt it will pass all of the above tests but only put out a fraction of its rated amperage.

Just beware, these are only quickie tests, not absolute tests. The 110V motor tests above might get the correct result with proper loading but I guarantee a hand drill won't turn the alternator once it's loaded fully.

Fri Sep 27, 2019 3:33 pm

I use this:

for a load. It has both a voltmeter and ammeter. With the 1 hp motor, can easily get 55 amps load. Side note: for a Harbor Freight made-in-china item, the quality, suprisingly, isn't half bad, and they will take the 20% off coupon on this item. Also works well for load testing batteries.