Not charging

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Feb 6, 2002
Surrey, BC
How do I tell if it is my voltage regulator or my alternator that is the problem?
I’m not charging my battery at all. (Battery is new and good)
Thanks !
77 FJ 40 stock 2F
First step is to either test your alternator with a multimeter or take it to Napa and have them test it. (Some bad alternators will test fine, but this is a good preliminary step)
The procedure for testing it yourself is quite simple, oulined in the Haynes manual and probably in the FSM as well. If you don't have this manual let me know and I'll type it up.
Come back with results for the alternator test and we'll go from there.
Hmmmm Just following this thread and picked up the Haynes book. 'Nother classic Haynes mistake. Testing in Vehicle... "Start the engine and increase it's speed from idling to 200 rpm" Damn... am I damaging my engine by idling at 650 rpm ??? ;~}

I've never done it myself, but remember way back in my pre-Cruiser days, someone mentioning that an oscilloscope will tell you real quick if you have lost a diode..... (hint for fellow pocket protector wearing & K&E log-log-duplex-decitrig slip stick toters: It's three phase before the diodes... which are less than perfect rectifiers. So, you can imagine what a an imperfect DC trace would look like on a scope...... It would look like baaaad DC. Just how baaaad would depend on how many rectifiers were kaflooey.)

If your coke-bottle lensed glasses are not taped together and you don't wear lace up dress shoes with your bermuda shorts, then please ignore my digressions.
Does it really matter? Rule of thumb is to change both at the same time. Neither are adjustable. Well, the regulator is but I doubt any of us can do it. As Bailey said, take the alt in and have it tested. Check all wires. Check voltage on the back side of the volt meter. Options are bad alt, bad VR, bad 10G wires from alt to batt to gauge, bad wires VR to ign or to batt. Could also be bad batt cables.
The alternator has a 3-plug connector with two wires going in to it. These two wires go into the regulator. There is also a third wire that goes into the regulator I'm not to sure where this one comes from. Also on the back of the alternator is the large wire held on with a bolt that goes to the fuse box.

I am guessing here, but I think the two wires that go to the regulator are sort of a relay that turn on the charging system (not sure if it is a simple on or off or a gradual increases or decrease of voltage) I jumped the two wires together to test my theory. When I look at the voltage on the battery with the engine off it is at 12.4 V, with it running it is at 12.35 V, with it running and everything on it is at 12 Volts. So there is no power going from the alternator to the battery with the connectors jumped together. I get the same results when I plug everything in as normal. If I unscrew the nut holding on the big wire on the alternator place the red probe on the stud and the black probe to ground would the voltmeter show me any voltage if I started the engine?

Sorry I don’t have a manual.

If it is the alternator, what other alternators can I use to replace this one for more power!?

Thanks for all the help. :D
My alternator gradually went out, replaced the volt. reg. and the alternator brushes (avail. from Napa), and it charges like a champ again. (Albiet with only 35 amps).
Check the voltage at the alternator by running the engine and touching the big terminal with a nut on it on the rear of the alternator with the positive of the multimeter, and ground the negative terminal of the multimeter. See what you get then.
If all the wires check out, I would then replace the alternator brushes and the voltage reg. See where that puts you. (brushes are cheap and easy to replace.)
Check the voltage from that big terminal at idle and again at half throttle or so. When mine was going out, it didn't charge at all at idle, but only above idle and when idling on an incline. (brushes too short)

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