Make Your Own Alternator Tester Cheap & Simple

It is a viable option. There is no way a benchtop-toy alternator spinner can test an alternator under load.

When was rebuilding I came up with a saying

LIFETIME WARRANTY: "Lasts as long as the customer's patience". Velcro & Wing Nuts

I am fascinated by three phase power. Not ready to make the modification when all seems to be fine.

My alternator did fail three years ago while on the road. Light came on the dash, dash voltmeter dropped a bit. Continued on a couple hours to the next town in WY. No shop could get me in so I changed it myself. Lifetime warranty from O'Reilly and on down the road I go. IIRC O'Reilly tested the old before selling me a new one.

path1 wrote:
Can anybody recommend a brand of diodes that is known top quality?

On another web site I like, many people end up buying alts from link below because they say they can't find any really good diodes to replace the bad ones they have. If top quality diodes could be found, they wouldn't have to spend big $$$ for new alt and just purchase diodes. (Personally I don't have that problem because I couldn't tell you one from another. I'm just going to pass info on).

Thanks

https://www.nationsstarteralternator.com/

Check this out...

http://www.ebay.com/itm/Alternator-USA-BUILT-Quicktifier-420-Heavy-Duty-External-Rectifier-Alternator/161242597226?_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D2%26asc%3D45702%26meid%3D6d035b54da904bad80accc8565921dd1%26pid%3D100005%26rk%3D1%26rkt%3D2%26sd%3D161173273360&_trksid=p2047675.c100005.m1851

A remote rectifier will VASTLY reduce the number of non-voltage-regulator-related failures.

And it is it's own built in battery separator eliminating solenoids, relays, or rectifier-based finned "isolators".

The stator leads inside the alternator need to be accessed.
The three stator wires need to connect directly to the new RRB remote rectifier bridge.

Give an example: Towing rig & 5th wheel. 160 amp alternator. Three ten gauge wires run from alternator to RRB mounted alongside trailer batteries. Full length of tow rig, bridge the hitch gap, etc.

So the trailer charging power is carried in the 3 new wires.

___________________________________________________________________________________________________________

What this does.

The original rectifiers inside alternator are only tasked to feed the tow rig. Zero wiring changes on the output wire to truck and battery

The trailer batteries see exactly the same voltage as the tow rig battery.

The trailer batteries suddenly see close to full alternator amperage potential when needed. Voltage drop is close to being all but eliminated. Neat huh?

The alternator rectifiers do not need exotic replacements or upgrades. Factory OEM grade will work fine.

Interior temp of alternator is substantially reduced at full load. And you know what that means...

Sell or trade the rig, off comes the remote rectifier.

Fiendishly simple, I like it....

Muy bueno!

Gracious señor.

Can anybody recommend a brand of diodes that is known top quality?

On another web site I like, many people end up buying alts from link below because they say they can't find any really good diodes to replace the bad ones they have. If top quality diodes could be found, they wouldn't have to spend big $$$ for new alt and just purchase diodes. (Personally I don't have that problem because I couldn't tell you one from another. I'm just going to pass info on).

Thanks

https://www.nationsstarteralternator.com/

The difference is this...

Unless an AC meter is actual peak-to-peak, it measures Root Mean Square. Combine that fact with adequately fast sample time and you are talking about an EXPENSIVE DMM...Capiche?

Throw enough money at something and miracles happen.

But this isn't the miracle mile. It's a forum where just buying a DMM is an event. And I have read threads where comments consisted of "Oh you paid ten dollars? I paid eight and at harbor Fright, sometimes they're giving them away as a promotion".

A $300.00 meter is going to be a hard-sell.

And cheap meters have sample rates 5 times to 10 times slower than a top quality meter like a Fluke. And RMS+cheap meter ain't gonna work.

Sooooooooo................................................................

One thing that WILL work beautifully, and is cheap is the listed analog meter.
There are no moving decimal points to configure into a reading. Teaching this subject to cruising sailboat captains and crew I know just how far technical can be pushed.......and it isn't far.

MEXICOWANDERER wrote:
A DIGITAL METER does not have a fast enough sampling (refresh) rate to capture ripple peaks.

I have to disagree with you. I've done this a number of times and know many others who have as well. It's a "normal" test for alternators ;)

Bear in mind I'm talking AC volts, not capturing it in the DC waveform like on an o-scope ;)

Edit: Here is Fluke's opinion on that.

Fluke ripple test

Hey! I got to contribute something...whoo-hoo! You're always helping me, now I get to return the favor :C

A DIGITAL METER does not have a fast enough sampling (refresh) rate to capture ripple peaks. This comes from experience not hypothesis. A .5 ripple proves nothing with the rectified WYE type modern alternators (8 rectifiers) example: Ford, 3, 4, 6G models. Lose the 2.2uf capacitor within the alternator and that .5 ripple limit will have you purchasing an alternator. ND, Mitsubishi, Delco - all he newer (read motorhome) alternators except for "some" Delphi models are 8 rectifier alternators.

The test is incredibly easy to perform
The meter is incredibly inexpensive
The meter is incredibly easy to wire with 2 little wires and two strong alligator clips.

THERE IS NO CONNECTION POLARITY TO OBSERVE. You cannot connect it "backwards"

Connect meter to alternator output stud and to chassis negative (ground) start engine. If that needle swings upward off of zero you have a problem. I suggest SAMPLING some good alternators and get a feel for this critter if you are unsure or have doubts about testing efficacy. The analog meter test is virtually foolproof.

A Ripple test only requires a DMM to check AC voltage. Over 0.5vac = bad diodes in the alternator.

Aside from the obvious testing of VDC to make sure it is charging, of course.

Are you saying to disconnect the vehicles wire(s) that are terminated at the alternator stud prior to connecting a 3v meter? Wouldn't it fry the 3v meter to expose it to 12-14v battery voltage through the harness?