My 79 FJ40 is not charging. The alternator and voltage regulator test good. I replaced the negative battery cable, just in case. Fuses all are good.

What other components do I need to be looking at? I'm pretty much a moron with electrical problems, so talk slowly. :D

1. Greater than 14V across the battery posts with alternator turning, then the battery probably won't hold a charge; replace it.

2. 12V at the battery with the alternator turning and greater than 14V at the alternator B+ lug (big wire), then there is a bad connection between the battery and alternator.

3. 12V at the B+ lug with alternator turning = bad alternator or regulator or the wiring in their circuit.

What does the ammeter in your dash read with the engine and lights on?

CHeck the alternator regulator, which is a small electrical unit mounted to the firewall that makes sure you don't overcharge your batt.

Always glad to help another 62 FJ40 owner.

First, I'd check the belt. If the belt is loose, it won't spin the alternator as much as needed (because it slips), and it won't charge.

Secondly, I'd replace the battery and cables. No sense in not keeping all the components fresh.

That should take care of your problem.

How about the wire connections to the alternator? I have an ongoing saga where whenever I do anything under the hood, the alternater wires disconnect themselves enough that they don't connect, but not enough to look like it. If that's the case on yours, try pulling the plug off the alternator and just connecting spade connectors.

Thanks for all the replies...

With the engine running I have 12V across the battery, and 12V from the larger B terminal.

When this first started, I took my voltage regulator to Autozone and they said it was bad. I then bought one of theirs and tried it. For giggles I brought the new one back and had them test it. It tested good.

I've had them test the alternator twice and they say it's good.

The belt is tight and the plug feels like it's plugged in good.

My ammeter doesn't work and hasn't since I've owned it. The needle even fell off of the gauge last year. :D

So, according to Pin Head, if the alternator and regulator are indeed ok, then I have a problem in the wiring somewhere. Great.

Jason, check for corrosion *inside* the jacket of the big battery cables, I had this happen a couple of years back on my Cruiser and while the alternator was charging, the corrosion was acting as a block to the current, impeding the right flow to the battery. I used marine components to make brand new cables and the problem was solved, also make sure you add a wee bit of dielectric grease to the connectors and cable ends before you install the shrink tubing.

Hope this helps!

If you are so sure that the alternator and regulator are OK, then you probably have a bad/corroded high resistance connection somewhere in the circuit. To find it look for the voltage drop across a high resistance.

Measure the voltage at the F terminal of the alternator with the engine running.

If it is 12V, then either the alternator is bad or it has a bad ground to the engine and back to the battery.

If it is less than the battery voltage, check the voltage at the F terminal lug (disconnect the wire) at the regulator. If you have 12 at the regulator lug, then the white wire with green stripe running from the alternator to the regulator is bad.

If you have less than 12V at the regulator F terminal check the voltage at the regulator + lug (the one with the black wire with a yellow stripe. If this has 12V, then the regulator is bad or it has a bad ground. If the Black/yellow wire is less than 12V then follow this wire back until it connects at the engine fuse in the fuse block. Obviously you have sufficient current at this point because your engine runs.

Cool, thanks Charlie!
Both ends of the F terminal were less than 12V. The regulator + lug has 12V, so I guess that means the regulator is bad or the ground to the regulator is bad.

How does the regulator ground? Is it through the body? I scraped some paint off of the mounting points and put some dielectric grease there.

Also, there is a loose wire coming from the regulator. The original one had that too. Anything I need?

Thanks again to everyone!

I forgot to mention it, but you need to check the voltage with the wires hooked up to the alternator or there will be no voltage drop. The regulator has a ground wire that is white with a black stripe that probably runs to the body somewhere close by.

The white wire with light blue stripe that goes to the N terminal on the alternator is the regulation current wire, but this one would only be bad if it was overcharging.

You can test the alternator by momentarily connecting the F terminal to the battery + terminal and checking that the voltage is greater than 14V.

OK, I'm back at this again after the holidays. Still no go.

I have my alternator plus two more in a parts pile. Autozone says they are "good", but I don't know what the output was.

Originally posted by Pin Head
You can test the alternator by momentarily connecting the F terminal to the battery + terminal and checking that the voltage is greater than 14V.
When I do this on all 3 alternators, I get 11.8 volts. So either they are all actually bad, or I'm doing something wrong on testing. I'm leaving everything plugged in, and sticking the negative probe into the F plug at the alternator.
I also get 11.8 at the B+ terminal.

What should I test next, or should I just get a new alternator?

I took the alternator to a different shop, who said that it was bad. So I bought a new (reman) one from Toyota. I still get 12 volts across the battery (12.2 - 12.4). I tested the new alternator at the F and B+ terminal and get 12 volts each.

That should mean that I have a bad ground somewhere, if I understand what PinHead was saying earlier. The voltage regulator doesn't have a ground wire - I guess it grounds to the body. I cleaned the mounting points some and added some dielectric grease. I also did this to where the new negative battery cable attaches to the frame. Earlier testing of the wires between the regulator and the alternator doesn't show any loss between them.

??

You still fooling with this? :mad:

What makes you think that it isn't charging? I mean maybe your volt meter is BS.

If your voltmeter is OK and you have 12V across the battery with the engine off and 12 V at the F and B+ terminal with the engine running at 1,500 RPM, then there is some problem. If you had a working amp meter it would help tell you what is going on.

The next thing I would do is disconnect the B+ wire at the alternator and check the voltage directly at the alternator lug with the wire off and the regulator hooked up. If it is still only 12 V and you have 12 V at the F terminal, try jumping the F terminal directly to the battery + post (only for a few seconds) and the voltage should go to 50-100 V or more if the alternator is working. Then hook the B+ wire back up and momentarily connect the F to the battery +. If you only get 12 V, then the battery is probably bad. If you get more, like 14-20, then the regulator or the wires to and from the regulator are bad.

I've tried two different voltmeters, including the new one I just bought (albeit a cheap one). I still get around 12.5V when running. Drops to around 11.8 with lights and heater fan on.

Disconnected the B wire, tested the lug on the alternator and got basically nothing.

Jumped the F terminal to the battery + with the B terminal still disconnected and still around 12V. Reconnected the B terminal, jumped the F terminal to the battery + and got around 16V.

:mad:

That is some strange shiit you are dealing with. Why not just put it back the way you had everything and just run it? Maybe 12.5 V will work out just fine.

Still would be nice to know how much current that puppy is putting out. If you feel ambitious and your multimeter is up to it, set in on at least 0-10A range and put the leads in series with the B+ wire from the alternator and see if it is putting out any juice. It may smoke the meter if it is pumping its rated 30A for long.