Voltage regulator?

[BeastMaster]

Yes. Full battery voltage at each of the two screws, with the engine off.

Well, that kills my belief of a shorted transistor.

Now, what's left is seeing what the F screw does during engine run. The regulator should pull it to ground when the engine catches, then let it go back up as the battery voltage approaches 14V.

 

[Selahdoor]

Well, that kills my belief of a shorted transistor.

Now, what's left is seeing what the F screw does during engine run. The regulator should pull it to ground when the engine catches, then let it go back up as the battery voltage approaches 14V.

I'll go try to set things up so I can test for that. My test leads aren't long enough for me to take the meter into the cab with me.


I must be doing the ASI test wrong.

I had one probe in the test lead that is clamped at the "F" bolt.

With the engine running, (And me pushing the test lead through the foam, with the connector still attached...), the voltage I got at each terminal was this...

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[Selahdoor]

I think you are on the right track with this.

Went out there and got it all set up so I could stand by the starter solenoid, and start it with a screwdriver.

Got the leads set up... Didn't matter whether I used the case of the alt as the ground, or the battery post itself... The voltage was now 1.24 volts. Not a typo. It was 12.7 before I came in, that last time.

Left it hooked up. Started the engine.... Stayed at 1.24, for a very short while, then started very slowly climbing. Topped out at 11.9volts.

While it was running, I checked the voltage across the battery terminals again. It read 15.63v.



Stopped the engine.

Battery voltage reads 12.36.

"F" to ground reads 12.36 again.

I'll wait a while and then go back out there and check again.

Oh yeah, when I come back in the house, I always disconnect the battery negative cables. So, when I went back out, the cables had been disconnected for a while.

 

[BeastMaster]

With the engine running, (And me pushing the test lead through the foam, with the connector still attached...), the voltage I got at each terminal was this...

Those voltages are way off. Meter set up for DC?

A should be same as battery voltage
S is a pulsating DC voltage if seen with oscilloscope.
I will be battery voltage, or ground if it's trying to light the "battery" indicator lamp.

Beautiful diagram. Wish I could do that in a timely manner.

 

[Selahdoor]

Those voltages are way off. Meter set up for DC?

A should be same as battery voltage
S is a pulsating DC voltage if seen with oscilloscope.
I will be battery voltage, or ground if it's trying to light the "battery" indicator lamp.

Beautiful diagram. Wish I could do that in a timely manner.

So, I did it right?

One lead, shoved into that tester thingy, so it was connected to the "F" bolt.

I probed the ASI and the square connector with the other lead.

Is that correct?

 

[onetonjohn]

You reading RMS voltage? This should be a rectified AC wave, right? I don't suppose you have a scope?

 

[Selahdoor]

I don't have a scope. Just a cheap multimeter.

Here is the full specs on the asi test.

The above was with the engine running.

Here is the same pic, but I added the "not running" numbers.

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Again, this is just a cheap multimeter set on 12v DC.

One probe connected to the "F" bolt. The other probe, probing the four connections, one at a time.

 

[BeastMaster]

So, I did it right?

One lead, shoved into that tester thingy, so it was connected to the "F" bolt.

Whoops. Just saw your post so I will edit my reply...

It puzzles me why not-running A S I is 0, 12, 12.

I expected 12, 0, 12.

 

[Selahdoor]

Uh, not quite.

I was thinking DC voltage to ground, but at least that helps explain those really unusual readings.

BAHAHAHAHA! Thank you. Why don't instructions actually tell you anything like that?All the instructions I can find LOOK like you are supposed to test between "F" and the other points.

So, yer saying I should get back out there and test between those points, and ground, instead?

(BTW: I said, up in post #62, that I must be doing the ASI tests wrong. )

 

[Selahdoor]

Oooooh... also just occurred to me. I'm going to make a longer lead for the f tester... get my meter set up on only the battery... (Where I still read 15.6 when the engine is running...) And see what it jumps to when I touch the "F" lead to ground...

 

[onetonjohn]

I think your multi-meter will have trouble reading AC. Probably not getting good readings. If you had a 6v rectified AC signal RMS would be around 4.5V.

 

[BeastMaster]

All the instructions I can find LOOK like you are supposed to test between "F" and the other points.

That's why I try to teach and show how something works instead of barking instructions. Once one sees how the magic works, he can throw the instruction book away. Any job is much harder if one is in unfamiliar surroundings.

 

[BeastMaster]

Got the leads set up... Didn't matter whether I used the case of the alt as the ground, or the battery post itself... The voltage was now 1.24 volts. Not a typo. It was 12.7 before I came in, that last time.

Left it hooked up. Started the engine.... Stayed at 1.24, for a very short while, then started very slowly climbing. Topped out at 11.9volts.

While it was running, I checked the voltage across the battery terminals again. It read 15.63v.



Stopped the engine.

Battery voltage reads 12.36.

"F" to ground reads 12.36 again.

I think you are damn close to nailing this beast.

You look at F screw to ground. Its right at battery voltage. Great. As it should be.

You start the engine. It catches. It begins spinning the alternator. The regulator sees it and drops the F terminal to 1.24V.

Great. As expected!

Then the battery voltage climbs to 15.63 V. While F terminal goes to 11.9V.

Here it is... F should have went all the way back up to battery voltage. It didn't. Why? Check A voltage. Is A voltage accurately tracking the battery voltage?

You've either got a corroded connection between A and the positive battery rail, or a bad regulator. If the voltage at terminal A is 15 volts and the regulator is still pulling the F screw down at all, that regulator is sick.

 

[Selahdoor]

That's why I try to teach and show how something works instead of barking instructions. Once one sees how the magic works, he can throw the instruction book away. Any job is much harder if one is in unfamiliar surroundings.

Exactly.

And now here re the real numbers for the ASI test. Looks normal to me... The two that are supposed to be battery voltage are. The two that are supposed to be 7v are close enough. 7.8.

Thinking maybe 7.8 instead of 7, is enough of a difference, to make it 15.6 instead of 12.6?



The "F" test....

Running. 15.6 volts at the battery. Meter is measuring the battery, nothing else.

Ground the "F" test wire... Goes to 18.4. Wouldn't say it jumps there. Jumps to 17 something, then quickly climbs to the 18.4.

Battery starts to boil.


Batteries are apparently barely boiling, on the 15.6v. So I do have to fix this overcharge condition.

I think your multi-meter will have trouble reading AC. Probably not getting good readings. If you had a 6v rectified AC signal RMS would be around 4.5V.

I'm not reading AC. I am reading the DC outputs from the alternator.

 

[Selahdoor]

I think you are damn close to nailing this beast.

You look at F screw to ground. Its right at battery voltage. Great. As it should be.

You start the engine. It catches. It begins spinning the alternator. The regulator sees it and drops the F terminal to 1.24V.

Great. As expected!

Then the battery voltage climbs to 15.63 V. While F terminal goes to 11.9V.

Here it is... F should have went all the way back up to battery voltage. It didn't. Why? Check A voltage. Is A voltage accurately tracking the battery voltage?

Yes. A voltage is always exactly what the battery voltage is.

12.3 not running. 15.6 running.