first stranding, alternator failure

jvandyke

jvandyke

True Classic
It's my fault. The car warned me.
Volt meter was low, I rigged up a second one, it was low. Put tester on alternator and it read 12v and no higher. I took off for work anyway. Slowly lost lights and then engine started to complain, pulled over and shut her down.
Now I was hacking the daylights out of my instrument cluster and messing about a bit in the relay nest but I don't think that had anything to do with it since a test right at the alternator shows it is not producing.
Any advice is welcome. I'm hoping to get a charge back in the battery and limp home to diagnose and likely put in another alternator.

Here's how it was hooked up and working fine for a month.

Brackets and "turnbuckle" look fine, belt seems tight, pully and alt fine spinning fine. Wire connections at alt look fine.

Any chance it's the "sense" circuit on the alternator? That line is currently just jumped over to the main lug of the alt so it "self senses" which is the traditional way to hook up a GM alternator, no?
This thing was flaky when I first installed it too, I actually pulled it back out, brought it in and it tested great, put it back on and all was well until now.
Could it be all the mucking about with lights pulled the battery flat enough that it wouldn't let the alternator "sense" enough voltage to start charging? I don't understand how that works, obviously...
I put the battery on a tender last night an it read "charged" right away, left there all night anyway.
Now, to get the X home I was hoping to put it on the charger (tender) which I brought with me for a few hours, get enough juice in the battery to limp home (about 10 miles).
 
I'm suspecting the charge line from the idiot light, it wasn't lighting up on reinstall of pod with key on, it never came on either even when volt meter was bottoming out. Maybe there isn't enough resistance through this to the alt so it won't charge. Does this make any sense?
I'm reading the sense line needs 35ohms of resistance, maybe my idiot light isn't providing this for some reason. Can I just get some sort of resistor to put between in series before the sense line to fool it? For now?

I have an emergency lighter socket light, I could cut off the socket and wire in the light, probably way more than 35ohm so though, I'm guessing a 10w bulb?
Or I'm reading the CS130 has in internal resistor so if that is the unused black wire, I can just switch wires and see what happens.
 
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I suspect my mucking about in the cluster disturbed the idiot charge light, either bulb is bad or connection somewhere is bad and thus the alt isn't seeing the resisted 12v it should, I'm trying to research to see if hooking up a light will provide the necessary resistance, or if I can use the F terminal on the alt, black wire instead of the L terminal (brown wire) which it seems may allow the alt to work off it's own internal resistor to self excite. Current (no pun intended) theory anyway.
Thoughts welcomed. Hoping to self rescue later today.
 
I got nothin', it does seem like there is something you have done to the cluster to cause the condition. I would trade the other cluster in and see if things change.

I am surprised you ran out of power so quickly, I ran my 850 over a hundred miles (during daytime and with no lights) last summer with a dead alternator. Of course an 850 basically uses no electricity since its points and mechanical everything after that...
 
I was a bit surprised too. I had a tender charger on the battery so I thought I would easily make it to work where I can plug in the charger again and fiddle. My kids needed the other car today or I wouldn't have risked it. Of course I was running headlights as it was dark. I think it's the charge idiot light line; bad connection or burnt bulb and that's all it takes for the alt to not produce I guess. I think I'll try to wire a light in there, that will provide resistance, or swap to the other feed (they say the L feed needs resistance but there is an F line that "may" take a straight 12v and resist itself....don't know) but I haven't confirmed that yet. I went through this same stuff with this alternator when I first put it in so I guess its picky about that charge warning line. Anyone want to suggest a good way to provide between 35 and 100 ohms of resistance? I'll try to figure out what wattage bulb would do that, or just a resistor, which I have 285 of at home.......
 
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On Bosch alternators, the D+ (sense) wire grounds the cluster bulb through the alternator, once the alt is producing voltage, the lack of a difference in potential (IE current flowing from both directions) causing the bulb no longer illuminate.

The GM one is different?

I would have thought that the alt would start charging once the rpms were high enough regardless of the idiot light wiring, but maybe it needs that 12v to trigger it?
 
That mysterious light...

The bulb is in the circuit to light up if there is current flow either way. But the bulb function is not required to make the alternator charge, all it needs is to be connected to battery (+) which it is on the other side of the warning light. This is why if the bulb is burnt out it doesn't charge, since the alternator doesn't see any 12v(+) if the bulb doesn't complete that circuit.

Not sure what the GM thing needs.
 
I believe so...

If I remember correctly when I first set mine up, mechanic told me to test for the original wire that gave you 12v with the key ON.

I used a replacment GM connector, 2 wires, white and red. Red went to output post of alt to give circuit to battery via starter.

White to the wire that gives 12v with key on. So a key on 12v supply in the engine bay to get you home? coil?

alternator.jpg
 
Based on this info and what I've found online, which says the CS130 needs 12v resisted down by between 35 and 350ohms, I am going to steal the emergency light from the emergency kit (glove box), cut the connector off and hook one one to a 12v source and the other side to the L terminal on the alt, the one one that would normally run to idiot light circuit. Thus I should be providing the alt with the resisted 12v volts to get it to kick back in. Now why can't I get that voltage right at the alternator's own ring terminal? What difference does it make if it's switched or not?
I have 12v in the trunk for the antennae, unswitched......

Found this:
"The charge indicator works in much the same way as on other charging systems-the indicator lights when the switch is closed, and then goes out when the engine is running. If the charge indicator is on with the engine running a charging system defect is indicated. For all kinds of defects, the indicator will glow at full brilliance. A new feature of this regulator is that it will cause the charge indicator to be on with the engine running if the system voltage is too high or too low. The regulator is temperature-compensated; that is, it's voltage setting varies with temperature."

seems like dead bulb or (since the bulb was good when I plugged it in) some other mishap has broken this circuit. I'll look for 12v from it at the alt with key on, if none, I will supply some resisted voltage from a different source and see what happens, if there is 12v there with key one, then well, I'm stumped. I read somewhere too that if the sense wire (S, the one connected straight to the output lug) doesn't see ENOUGH voltage it will shut itself down, now how that can be a "feature" I don't know, your alt shuts off if the voltage drops? Seems like that's about when it should get busy, no?
 
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35 ohms at 12V is about 4.1 watts

so 5 W bulb will do (it will be slightly less tha 35 ohms) but it should be OK.
If you were running lights then the battery will drain pretty fast....
 
switched/unswitched

I don't know what affect this would have if you use unswitched power to that lead. You know the battery is connected back to the alt via starter, so there is constant power there.

Would an unswitched trigger for the alternator leave it hot all the time and burn it out? I realize this is just to get you home, but I still wonder what the affects are....
 
I did the hack on the lighter emergency light. Didn't seem to work but I had enough in the battery to limp to job #2. Once there I reexamined the set up and found the bulb loose, tightened and it lit, fired up car and voltage shot up to normal.....so on the right track, must pull cluster and see what went wrong with the OEM charge light. At least I should get home. Feeling like McGiver over here!
I did use the constant hot from the antenna but just now disconnected it for fear of leaving it on not running.
 
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Did you get home all right? You are welcome to borrow my battery if you need it, let me know.

Karl
 
At job #2 until 8 but now that I know I can fool the alternator into producing juice, and it is on a charger as I type, I feel pretty confident I'll get home.......with lights on even. :sun:
 
jvandyke said:
I did the hack on the lighter emergency light. Didn't seem to work but I had enough in the battery to limp to job #2. Once there I reexamined the set up and found the bulb loose, tightened and it lit, fired up car and voltage shot up to normal.....so on the right track, Feeling like McGiver over here!
Click to expand...

Good news! Glad to hear you worked out a solution (even if a temporary one) :thumbsup:
 
Made it home. Alt put out full voltage the whole time, lights were bright and all systems happy. Now to go out in the freezing cold garage and attempt a proper fix. Thanks for input everyone. If it gets home under it's own steam at the end of the day, it's a good day.:guitar:
 
jvandyke said:
Now why can't I get that voltage right at the alternator's own ring terminal? What difference does it make if it's switched or not?
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The exciter circuit will draw power from the battery when the engine is not running; if you supplied unswitched power to this circuit you'd run down the battery when the car is parked.
 
Took cluster back out, swapped bulbs around. I think it's a contact issue with the holder since the bulb I took worked elsewhere, don't know. Idiot lit with key on, undid my McGiverisms. Drove to work with full voltage and REALLY bright interior lights. All is well again. Next.
 
Congratulations Jeff!

So, do I understand the root-cause correctly? If the 12v resistive load is not applied to the alternator (thru the dash warning bulb circuit), the alternator will not charge the battery? Does this mean every Fiat X1/9 alternator will stop functioning if the alternator dash warning light bulb burns out?
 
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