Ok,

so, had the charging system checked out on one of those machines, and they gave me the print out - all was fine with both the battery and the Alt.

So, now I'm wondering if it's not just the sending unit/wire to that light on the dash?

Does anyone know that wire/sensor begins? I assume it's a single wire, correct?

doesn't seem like it's overcharging either, since it was 14volts at idle, 12.75 on the battery car off, and when a load was put on, the alt increase amps (ran it at 2K RPM for a minute with high beams on, heat fan on high, etc...

I'm trying to get to the bottom of this - I'm guessing something happened when I pulled off the gooseneck and let the water drain out when I changed the Tstat and engine temp sensor last night... all that is fine now... no leaks, temp is fine, etc...
now if I can just get rid of that light on the dash :-)

Thanks

 

Heres how it works when all is well:

KOEO the voltage regulator grounds the voltage from the idiot light & the light turns on.

KOER charging begins, the ground is removed & the idiot light goes off.

If a diode is shorted out the idiot light should-i believe-come on dimly & you will see AC voltage at the battery.

Did they test for AC voltage as shorod mentioned in your other thread?

The wire from the idiot light to the alternator is probably light green/red stripe. If its shorted to ground that would also turn the idiot light on. Try wiggling it. Does the light go off?

 

oh, so it plugs into the alternator directly? (the wire from the idiot light)

Yeah, KOEO - you see it there, and KOER it's still the same brightness...

So, am I checking AC voltage at the battery then, KOER? at idle?

I don't think they checked this - they just checked the alt to see if it was putting out decent amps under load, and at idle vs 2K RPM

Thanks

 

Yeah, check for AC at the battery with it idling.

The idiot light is wired from the ignition switch to the light & to the voltage regulator which is part of the alternator.

Try to trace that wire & see i theres a bare spot thats shorted to ground somewhere.

 

if I poured water all over the top there, to disapate the antifreeze, and then started it, would that have fried the voltage regulator in the Alt? and causing it to ground out like that?

I was told I could just replace the that part of the alt? is that hard to do? $15 or so for a rebuilt kit? or what?

but, if I get any AC at the battery at all, it's most likely a diode that failed?

Thanks,
Bob

 

Before we do anything else did you ever check that fuse I mentioned in my 1st post? That fuse provides exciter voltage & it wont charge & the idiot light wont go out if it's blown.

From the test you had done it "sounds" like it's charging. But who knows.

Your owners manual should list it as the "Generator/voltage regulator fuse".

 

Since I'm not a moderator here I cannot merge your two threads together. For future reference though, mediaman67 there is no need to start a new thread with follow-up information to your existing thread. This makes it difficult for people that use the search feature to get the full story.

-Rod

 

would it be in the side of the drivers side dash there? or another place?

I mean, I checked the volts myself too - I had 14+ at the battery at idle, and with the car not running, it was only 13...

I guess the real test will be if the battery drops below 12 volts after it's been driven for 1/2 an hour :-)

but, I'd love to have this only be a fuse...

anyone have a location and a blow up of the box, so I know exactly where it is? :-)

Thanks all

 

Yeah, 14 volts is good.Try removing the connector from the alernator & turn the key on but dont start it. If the idiot light stays off, i think you probably have a shorted diode.

 

and I will check AC at the batt too when it's running as well... you give some good info, I'd say it's either a failing rectifier (diodes failing, etc) or the voltage regulator - or maybe something as simple as a bad connection at the alt....

but I thought that they way that light is wired, is that it shorts to ground if it is not seeing 12v from the alt, meaning that it is on all the time, unless the alt is spinning, giving it 12v on the other side? I would think that if I pulled it, and checked KOEO, it would still be on.

or are you saying the larger connector, the 3 pin one? I was just thinking about the small single wire one (for the light on the dash)

Thanks so much - hopefully, I can get to the bottom of this tomorrow for sure with your help :-)

 

The factory wiring diagrams that i have are for my 97 It shows a single wire alt output to the fuse links & a 2 wire connector one wire from the idiot light and the other to the excitor fuse that I mentioned.

At KOEO voltage flows from the ignition switch thru the idiot light & is grounded by the voltage regulator. Idiot light is on

Start the engine , the voltage regulator removes the ground & the idiot light goes off.

What you really should have for this-& your next electrical problem- are the factory wiring diagrams for your 96. Helminc.com has them for around 20 bucks.

I like doing things the easy way, which is why I have the factory wiring diagrams for all my Fords

 

Yeah, I have the complete book for my Aerostar, and I know just what you mean - much easier when you know which wire you are looking for (green/white stripe, etc)- came in handy when I was doing the audio system over in the van...

So, I guess the question is, if I had a bad voltage regulator, would it not allow me to get my 14+ at the battery with KOER? - as I said, I did a load test, and it did put out more amps under load, higher RPM, etc so I would assume that was the voltage regulators job to determine how much power to give the system on demand? More load requires more amps for the same amount of power, etc...

I'm just trying to troubleshoot this from a logic standpoint -if it's only a bad wire, etc, and not getting the 12v when the Truck is running to turn off the light, I don't care as much as if the voltage regulator is fried.... seems like that would be a good thing to have working correctly, but maybe it already is, and I just have a bad wire?

 

Glad to hear you have some really good wiring diagrams foryour Aerostar. They make life so much easier when looking for electrical problems.

The bottom line with your idiot light is that the voltage from the bulb is being grounded somewhere & keeping it lit

Thats why i suggested removing the connector from the alternator & seeing if the light goes out KOEO.

If the light goes off I would replace the alternator.

If it stays on i'd look for a short to ground in the wire between the bulb & the alternator.
Yeah, since it's charging as it should AND the idiot light is staying on this IS a real puzzler so in the future could you please keep your problems to yourself. Just kidding

Are we having fun yet?

BTW the way ive always found Ford alternators to be very reliable. So a used alternator from the bone yard would probably be a cheap & safe way to go.

 

Ok...

This morning I decided to pull the unit and change out the Voltage Regulator and new brushes too while I was at it, I cleaned the slip rings too...

put it all back together, and THE LIGHT IS STILL ON!!

Checked AC at the battery - 000 - nothing, so the rectifier is fine...

Re-Checked the new VR and brushes - 14+ at Battery KOER - same as it ever was...

87... I DID unplug both the little 2 conductor plug and the bigger 3 conductor plug, and KOEO, the light was gone... if I unplugged just the little 2 connector, but leave the one that is the bigger 3 connector plug, it stays on still

at least I now know that the alt has a new VR and brushes, and is fine - but the light is going to bug me now, esp when I just spend $50 and replaced something that was fine...

I agree with you on Motorcraft in general - my 89 aero has the original Alt, and just for fun, I checked it today, and at idle, it's still putting 14+ volts to the battery... and it's 21 years old!

what about this darn light! I'm about ready to pull the bulb, but that requires tearing apart the dash board, which I need to do anyways, since I wanted to replace those 6 night time lights for the cluster, etc...

Any other ideas from 87, 96, etc are very welcome at this point... :-)

any chance 87, that it could still be something stupid like that fuse you were saying?

 

Yeah it could'nt hurt to take a quick look at that fuse. If it's not blown I think you've proven that theres some sort of problem with the alternator.

If your 96 is the same as my 97 the fuse is number 6 15 amp mini fuse under the hood in the power distribution box.

Gotta hate when you buy a new part & it does'nt fix the problem. But I think you have pretty much zeroed in on this being a whacked alternator since the idiot light stays off when the alternator is removed from the circuit.

Congrats on all your hard work on this idiot thing.