Thread: Charging system failure.

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Hello all,

I have a 1980 Toyota truck that was just acquired. It does not charge. The previous owner just put a new alternator and a new regulator into it. They don't even have dust on them. But there is no charging AT ALL.

The alternator has the big output stud sticking out the back and then a three wire connector.

I briefly connected 12V to each of the three connections on the back of the alternator. One of them causes the alternator to put out BIG TIME. So I believe the alternator is okay.

This leaves the wiring between the alternator and the regulator. The three wires from the regulator go up to a plug. They have continuity from the alternator end to regulator end plug. At the regulator plug one wire doesn't go thru because the regulator side doesn't have a matching wire.

At this point I opened the regulator but there is no figuring out what is happening under all that potting compound.

So I got a new regulator and plugged it in. No joy! Still not charging.

If I jumper from the HOT wire at the regulator connector to the little green wire(regulator unplugged) then the alternator again puts out maximum.

At this same connector one wire is always hot.

One is switched hot.

While the regulator is hooked up and the engine is running one wire is also at 11V.

One is at 10V.

The charge idiot light has never been seen and if I connect every wire in the harness to ground thru a 12V bulb the idiot light still doesn't come on. Should it?

Can the idiot light being burned out cause the alternator to cease output?

What are the three connections on the alternator? I can relate to a Delco alternator with the HOT stud and a field connector and the R connector for the idiot light but I can't figure out why the Toyota needs 3 wires plus the hot stud.

I purchased the Chiltons but all it has is a schematic showing:
Hot
Switched hot
Idiot light
and three "other wires between the regulator and the alternator but not what they do!!

With the regulator hooked up and engine running I never measure any voltage on that one wire that forces full alternator output.

Any suggestions?

Thanks Denny.

I will shoot it up tomorrow morning and post pics here.

Here are shots of the system.

er...once I remember out how to post a picture!.. Grrr!

Oh yeah the reply page!!

Other mentions..

That little harness is for what?!?!? It doesn't transpose any connections the existing original cable plugs into the alternator just fine. ...

Using it or not using it makes no difference in my results.

Why would the original charging system be completely replaced with no functional improvement? Speaks to wiring problems.

Note the frayed bare black wire on the vehicle harness. odd...
Disturbing... I removed a couple of inches of tape that stopped right at the bared wire.

Man all Jap charging systems are fused, first thing ya need to do is go to the fuse panel and check the fuses, You wouldn't be the first guy to rack his brain on one of these just cuzz the fuse was blown......

Can't be the fuse because the same fuse that runs the ignition and umpteen other things is the fuse to the regulator.

We jumped from the hot stud on the alternator to the plus battery terminal directly, which by passes the fusible link too. With no suck sess.

I just spent an hour at the library looking at the schematics. They all show the regulator with all these labeled connections F,E,B,etc,ect but of course both of the new regulators just have some frikken wires sprouting out of them into a flying connector with no labels. And of course none of the wire colors on either regulator have anything common with the schematic colors!!! ARGH!!

If the light isn't coming on ever, I would change it. The idiot light has to be working because this is what 'primes' the alternator to begin charging. When the ignition is turned on voltage flows through the light, through the regulator to the field wire on the alternator.

Originally posted by califgrrrl
If the light isn't coming on ever, I would change it. The idiot light has to be working because this is what 'primes' the alternator to begin charging. When the ignition is turned on voltage flows through the light, through the regulator to the field wire on the alternator.

Purty smart for a gurl (lol)

Man my stuff only goes back to 1983,but looking at that it says fuse #12..15 amp is for charging system & emission control, also looking in the locator there is a charge lamp relay located in the right kick panel
looks like 3 wires go to it a white/black wich goes to ground,,a yellow, and a yellow/white.....hope this helps.

Originally posted by HWORRELL
Purty smart for a gurl (lol)

Duuuuh, well thank yew...

Yew ain't so bad yerse'f mistur H.

Seriously, that relay would be a good thing to check also. Seems like he's ruled out almost everything except that circuit.

HWORRELL; I re-checked that fuse situation.. You are correct I was mistaken, there is a fuse that runs only the alternator and a fuel solenoid and sumptin else like carb heat. It was an incorrect 10A fuse even tho all the books and the fuse cover say 15A . It wasn't blown and I replaced it with a 15A. But it still made no difference.

We rechecked the all the signals with respect to the harness plug from the dash and all the signals "seem okay" with the exception of the charge lamp???

We stripped down the wire housings down to the alternator from the regulator plug, so we could actually lay eyes on the wires and they all look okay.

califgrrrl; Is that charge light some strange voltage like 2.763734453V bulb or is it a 12V bulb? Is there a way to test it without pulling the dash apart, groan....?

Hmmm charge lamp relay?? Steewpid! Just give me a Delco with an internal regulator..

I will look again at my schematic to see if there is a charge light relay in this model year. Thanks.

It's possible that the light could be less than 12v, that may be why there is a relay. There should be 12v going to the field wire with the key on.

AH HA! That is some info I was after. I wasn't sure when the field should be energized with the key or with the alternator spinning.

We get goose eggs going to the field wire outta the regulator which is of course the tragic result of The Problem. I will be checking that light/relay situation as soon as I get back to my shop.