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1982 Toyota Pickup Alternator

My genius number 3 son brought home a 1982 Toyota 4x4 pickup to build into a mud truck or rock crawler, etc. Mostly is a yard ornament at this point. The truck was missing the original alternator and someone had wired in a Chevy single wire, and done it very poorly. Is there anyway to find out what the original alternator was and how to re-install the same? I have spent lots of seat time searching but there seems to be several different possibilities. Any guidance would be appreciated… I need the lawn ornament our of my yard! Thanks from Idaho.

Any parts store will have a listing for the alternator. I suggest a trip to a junkyard that has a similar '82 to see if the alternator brackets were altered and what wires may be missing. The original Toyota alternator had a three wire connector that plugs into the voltage regulator. If this connector is missing on yours, you may need to replace the wire harness to get the original style alternator back in.

It might be a good idea to pick up a copy of the Haynes Repair Manual for the Toyota. There was only one size engine that year but 2 alternator choices…a 5 wire 40 amp and a 6 wire 50 amp. Both have external voltage regulators. Here is what they look like.

Thanks for the ideas… The voltage regulator is still on the fender well and the wiring harness appears to still be hanging. What is missing besides the alternator is the adjusting bracket so a junk yard is a great idea. Thanks again.

I have a 1982 Toyota pick up.
I changed out battery and alternator. Voltage monitor reads that battery is only half charged. When driving to work today the battery voltage went to zero. When turning hi beam lights on .truck would dog out? very low lights and fuel gauge read empty?
Could I have gotten the wrong battery or bad alternator? Or is it my Voltage regulator . In which i am not familiar with?

Can’t tell from here. But any shop should be able to diagnose this pretty easily. They’ll want to test your battery and charging system (alternator and regulator) for starters.

I recommend that when you have a problem you start a new thread rather than resurrect an old one. Having more than one question on the same thread can confuse everyone, even of the thread is an old one and the vehicles are the same.

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Not sure what you mean by that. The only way to determine the charge state of a battery is a battery load test. That’s done by a shop, not usually a diy’er test, needs special equipment. The battery voltage itself isn’t a good indicator of the battery charge. But the other things you say indicates you have some combination of a battery or alternator problem still.

Here’s where to start. With the engine off, measure the voltage directly at the battery terminals. Using a DVM from the engine compartment in other words. They should measure about 12.6 volts. What do yours measure? Now start the engine and let it idle. Measure the voltage at the same point as above. It should now measure 13.5 to 15.5 volts with the engine idling. What does yours measure?

Thank you for you response. I have found out that when we replaced the battery and alternator . Voltage regulator failed in the alternator. We will need to replace alternator again. Does this happen often? I was not aware that the voltage regulator was part of the alternator.

My 40+ year old truck, the voltage regulator is a separate part from the alternator. My 20+ year old Corolla, the voltage regulator is included inside the alternator. Fro the most part newer cars have the voltage regulator inside the alternator.

The way an alternator works, a coil of wires is rotated through a magnetic field. By the laws of physics, that motion produces electrical current. The problem the car designers had was that they need the alternator to produce the exact amount of current needed at the time, no more, and no less.

The faster the rotation of the alternator, the more loops in the coil, and the stronger the magnetic field, the more current is produced. Since the number of loops is fixed, and the rotation speed of the alternator is governed by the engine rpm, which varies according to how fast the driver want to go, the only way to control the amount of alternator current output is to vary the strength of the magnetic field. That’s what the voltage regulator does, by changing the amount of current in an electro-magnet, it changes the strength of the magnetic field to exactly meet the needs of the car’s electrical system. A pretty clever gadget. There’s fragile diodes and transistors in the voltage regular, and if they get shorted out, hooked up to a battery w/the wrong polarity, subjected to voltage spikes, or get too hot they can fail. Or they can fail for no apparent reason. It is somewhat unusual for a voltage regulator to fail though for no reason, I’ve never had one fail before. Probably the most common reason they fail is when accidentally hooking up the battery w/the wrong polarity, or when using your car to jump start another, or getting your own car jump started.

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Great input.Impressive

Toyota has a plug on the back of the alternator. That line has wires that run voltage to the alternator to ‘energize’ the regulator and trip the battery light. If the battery light is not on, but the voltage is not greater than 12V, that plug is either not seated properly or a fuse is blown that feeds the wires to the plug. Check those first.

It happens occasionally. My guess is that this is a rebuilt alternator. That does save money, but they can fail occasionally. [quote=“patmaddenathome, post:8, topic:53049”]

I was not aware that the voltage regulator was part of the alternator.
That’s the common way to manufacture them now. Has been for decades. It’s apparently less expensive to manufacture the components in an integrated unit than to manufacture and install them separately.

Voltage regulation is handled by the ECM on many? most? all? late model cars.

Good morningWhich fuse would I look for if this is occurring?

What fuse will I be looking for?
Any of them that failed?
Thanks again,
At least I can look for something? I I changed out the “new” alternator this week end.
Seems that I am still losing voltage charge in my battery?
I will check fuses.

What happened that makes you think this?

The GM alternator should work fine; correct fitment or not. These are as simple as it gets. Over the years I’ve done a number of GM alternator fits to various non-GM cars for any one of a number of reasons and never had an issue with any of them.

Turn the key to the RUN position; engine not running.
The battery light on the dash should be on.
If so, touch the alternator pulley with the tip of a screwdriver. You should feel the magnetic attraction of the pulley.
If so, the alternator should charge assuming the circuit between the alternator and battery is good.

Granted, that is as backyard as it gets but… :slight_smile:

Car talk, Have replaced alternator twice. Still not holding a charge? Went back to O’reilly and checked alternator. Yes voltage regualor failed. will need to replace again/ This time they will check alternator before I replace into truck.
Ids this common?
Very frustrated. Could there be something that is making the voltage regulator fail?

I think I would be investing in a voltmeter (digital VOM). It would be a big help to know what the output voltage of your alternator is. Then you can start narrowing down where the problem might be. I’m sure you can find one for $20 or so. Good for testing fuses too.

Failing voltage regulators galore? hmm … well, the VR outputs quite a bit of current to the alternator’s field coil winding. That’s the part that goes round and round inside the alternator, physically connected in one way or another to the alternator pulley. Especially so if there’s a lot of demand for electrical power, like the battery is discharged and the headlights are on bright. So if it was having to output a lot of current all the time for some reason, this could burn out the VR I suppose. Or if the VR wasn’t attached to the alternator via the designed-in heat sink to keep the VR cool. Or if the alternator’s fan was blowing the wrong direction. Seems very unlikely.

Here’s a guess: there’s a short circuit in the car’s wiring harness somewhere that’s forcing the alternator to produce a lot more current than it was designed for. And that’s forcing the VR to output max field current, and that’s making the VR hot and burning out the VR’s field current producing circuitry. This wouldn’t show up if you took the alternator someplace to test it on a test fixture, as the problem is with the car’s wiring. It should show up however with a standard charging/battery system test. They measure the amount of current the alternator is producing for that I think. If my guess is correct, it will show your alternator’s producing a lot more current than other cars.

Edit: Years ago I purchased a clamp on DC amp measuring gadget that simply measures the magnetic field produced by the current and deflects a needle which presumably has a magnet attached to it. It is pretty accurate, and it didn’t cost very much, less than $10. You can either measure to 80 amps full scale or to 10 amps as I recall, depending on which slot you put the wire in. Might be a good tool for your situation, if you can find one. I think I purchased mine at Sears. But like I say, this was years ago.