coryc85

Has anyone ever come across a component level test procedure for the alternator regulator? My charge and brake lights came on, I saw my alternator soaked with what I think is power steering fluid and years of mud and whatever else. Brushes are not that old and they still look good, I cleaned the heck out of the alternator, took it apart, cleaned and brushed all the contacts and the entire alternator. Put it back together and took it to the auto parts store to test before I put it back in the truck, it failed immediately, but I suspect maybe the parts store kid did not know what he was doing. The screen kept asking if it was connected and the ground was connected, and I could see that it was, but I'm not sure if the setup works or if the pigtail was the right one or who knows what else. Anyway, so I brought it back home, disassembled it again and went through the tests from the FSM. Ohm'd out the stator, Ohm'd out the rotor thru the slip rings, checked for shorts to ground, and then finally did the rectifier diode check. It appears one of the positive side diodes in my rectifier was blown, meter was not indicating the .5V diode drop that the rest of them were. I had another denso alternator, which I disassembled and checked its rectifier and it passed the tests, so I swapped rectifiers. Only part really remaining to check is the voltage regulator. I did a little test where I connected 12V to the battery post on the regulator, then measured the voltage at the lamp pin, it was nearly 0V, then I applied 12V to the IG pin and the lamp pin voltage showed 12V, which I think would be correct, that would turn the lamp ON when ignition is on. So there are a few more things to check, but not exactly sure of them. I want to check that the regulator does indeed regulate at 14.5V or so, and I want to check that the lamp pin goes low when alternator starts generating voltage.

And if my regulator ends up bad, do people replace them with aftermarket or is there a DENSO available?

scope103

I'm not a big fan of YouTube as a reference, but this video may be what you need:

You said you did the FSM tests. http://web.archive.org/web/201102051.../2onvehicl.pdf
Did you ground the F terminal? As I understand it, that bypasses the voltage regulator asking the alternator to put out as much as it can. If the voltage rises with the terminal grounded, the regulator is suspect.

However, you have the operation of the "L" pin (Lamp? aLt?) backwards. The "other" side of the Alt light is connected to 12v with key-on. When the alternator is not turning, the L pin is GROUNDED, which allows the Alt light to turn on. When the alternator is producing (sufficient) power, the L pin is at 12v. The Alt light has 12v on both sides, so it does not light.

RockAuto has reman Denso Alternators for LESS than the cost of just a diode/regulator assembly. Go figure.

coryc85

Thank you scope for the reply...I will check my Lamp circuit again, I did not look at the wiring diagram, so thanks for setting me straight there.

I did NOT run the FSM tests on-vehicle before taking it off, I wish I had done that. I only did the tests in the Charging section, ohm'ing the stator windings, rotor, checking for short to ground, and the rectifier forward voltage tests. Now I'll go back and recheck the Lamp operation. I can't watch that video here at work, it's blocked so I'll check it out tonight.

Not sure if I want to chance a reman'd or not. Since one of the rectifier diodes failed the test, I'm kindof hoping that was the only problem and the alternator is now working, but I didn't want to install it just to turn around and pull it back out again if it's still not charging.

Terrys87

iTrader: (1)

The last re-maned alternator I bought I wound up using for parts to fix my original alternator. Most are rebuilt in Mexico and they had several different screws instead of all of the same. Part store is about $100 for a rebuilt and I can get mine locally rebuilt for about the same price and it is a far better job. Shops that rebuild them are getting harder to find then what it used to be so you may need to look around. I have to go 40 miles to get one rebuilt.

coryc85

SUCCESS! So I watched that video that scope linked, and it's not exactly the same as my regulator, but the tests should be similar. Basically, I soldered some wires to an old taillight bulb and then clipped the wires to the regulator terminals where the brush holder would normally connect. Then I connected 12V from my battery, + to the battery terminal on the regulator and - to the body of the regulator. Then I jumpered +12V to the IG pin on the regulator, and that lights up the bulb. I believe this simulates the regulator allowing current to flow through the rotor of the alternator. Next, I used an 18V drill battery to do the exact same test, the point of this would be to see that above 14.5V, the regulator shuts off the flow of current through the rotor. My regulator failed this part of the test, the light lit up even at 18V. Again I went to my spare alternator, same one I scavaged the rectifier off of, took its regulator and I performed the same 2 tests. This regulator passed both tests.

So then I put the good regulator into my alternator and took it over to Autozone to have it tested. It passed their tests, so I will be installing it here over the weekend.

Pandamator

Thanks for this!
I built myself a variable voltage output to do this very test, and am very excited to try what you have just done
My question is, when you used the 18V battery, did you run 18V through both +ve pins with a common ground connected to the underside of the regulator?

coryc85

Been a while since I did this, but yah common ground, I used body of regulator. I connected the 18v to the batt pin and I think to lamp pin. No current should flow so the test bulb should not light up if regulator good.

Pandamator

I was unable to make current go to the brush terminals and not sure why. I'll have to keep trying.

I was able to do the following test I watched someone doing while narrating in a language I could not understand. Here is my write-up of what I saw and then tried myself (it works)



Setup:

12V AC Power source (PS)

Test light connected to the positive of PS

One more wire connected to the positive terminal of PS (call this X)

Steps:

A. Join together the battery constant post (heavy white wire) and ignition terminal post (black-yellow wire)

Connect them to positive of power source

Connect negative from power source to the negative pole below the VR or to the VR body

B. Hook up test light to light terminal (yellow wire). It should light up

C. While the light is glowing, touch the X wire to the Stator terminal on the VR – the one furthest away from the plug socket. The light should turn off now.

D. Hook up test light to the F (brush) terminal on the body of the VR (not the B+ one on the plug socket)

The test light should shine dimly.

E. While the light is glowing, touch the X wire once more to the Stator terminal on the VR and the light should become brighter. I noticed that my voltage dropped on the meter I had hooked up.

Of my two voltage regulators, one passed this test and one failed. Its test light didn’t come on at step B.