Temperature sensitive charging issue??

Stangswagalicious

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Aye YUH. whats up wit it fams??

So, heres the story. Iv been a mechanic my whole life. Been wrenching for comming up on 16 years. A few years professionally even. And i can honestly say. That for the first time in my life, my shit box is doing me dirty and i can NOT figure it out

This is what i know:
Bought the car, did a bunch of work to get it reliable and wouldnt you know it, as soon as everything is going good, the 26 year old alternator takes a dump. Started showing 11.5 volts on the pillar gauge. So i replaced it. Easy right? HA!!!

New alternator goes on. Charges fine for a couple days then boom. Back down to 11.5 volts (which is less than battery voltage every time iv ever checked battery voltage). checked the commin grounds, cleaned battery terminals and it was all in vein. Warrantied out the alternator for another new one. Same thing. Seems to work for a day or 2 then back to 11.5. Only on this 2nd one, i noticed that the alternator would charge (14.5 volts) as long as it was warm outside. Had a few warm days so i didnt pay it any mind. Because it was working. But were back in another cold spell here in the great midwest and now im just sick of it. Replaced the alternator again. Only this time, i did it on a cold day and low and behold, first day it did its job just fine. Next day, back down to 11.5 again. F*€kn WHYYYYYYY

other random facts and helpful info:
When its not charging, the car is definitely running on battery power alone. Lights are dim, wipers move real slow, fan doesnt blow as fast, ect. And when this happens the voltage always starts out at 11.5 but will just keep dropping lower and lower as the drive goes on

Any time this happens, as soon as i get home i plug the battery up to a trickle charger. Dead batteries are NOT happy batteries

Also, the warmer it was, the better the chances that it would randomly start charging properly at some point throughout the drive. did this many o times but if it was too cold it would never charge at all.

Iv heard of the fusible links. But like… if its bad how could it work sometimes??? Lastly, my educated guess tells me its either faulty voltage regulators (but honestly… 3 in a row?) OR, whatever is actually communicating with the voltage regulator is on the fritz. Has anyone ever experienced something like this??

Questions that i cant find answers to:
What is actually controlling/communicating with the voltage regulator? (Whats on the other end of the wires connected to the voltage regulator)

Can a fusible link be half bad and work sometimes? Doesnt seem realistic to me.

Anything at all helps. I could definitely use some help on this and would appreciate any input at all
 
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Stangswagalicious

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Also, i guess i should mention its a 95. So i gots me a 5.0. Motor is factory other than parts replaced with oem parts. No power adders or anything.
 

ttocs

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I had a problem with my throttle position sensor showing that I had 4-6% throttle while at idle and I am outside of the car. So I swapped it out, reprogrammed the new one to the holley hp and it fired right up. Then during a remote turning session once it got back up to temp it started to show the same thing. Turns out it was the harness going to it was old and as the motor got hot it would create resistance that the ecu reads as it opening a little.
 
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Stangswagalicious

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So, heat creates resistance right? But if thats the case, when its warm out, it works like it should. When its cold it doesnt work at all. If its like 60 degrees it will eventually randomly start charging. I believe your take away is the harness. Which tbh i have not checked yet. But… i just cant see how that could cause an intermittent issue and not a permanent one.
 

95opal

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The alt wiring also goes to warning light in cluster. Problem there and it won't charge. Green wire
 

lwarrior1016

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I would definitely start by trying new wires to the alternator. Run a new wire from the fuse box to the alt, see if it changes. Then go after that green wire that Opal is talking about. You can run straight ignition power to that wire to see if it’s a fault in that circuit.

I don’t recall if you have a 3g alternator or not, but if you do, grab a spare connector and make a “1 wire” setup with it. Fresh 4ga wire from the fuse box, then hook the new connector with the yellow and green wires hooked right up to battery power. That’ll tell you if it’s charging, some folks have said it drains the battery when it sits because the alternator is always energized.
 

ttocs

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So, heat creates resistance right? But if thats the case, when its warm out, it works like it should. When its cold it doesnt work at all. If its like 60 degrees it will eventually randomly start charging. I believe your take away is the harness. Which tbh i have not checked yet. But… i just cant see how that could cause an intermittent issue and not a permanent one.
I think you have that backwards, resistance builds heat but a hot wire doesn't have a different resistance from a cold piece of wire. Now heat can make the connections at the harness expand, that expansion can cause resistance and then that resistance builds heat.
 
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Stangswagalicious

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Started it up today. Almost 70 degrees out. Charging just fine. I dont think it has a 3g alternator. Then again, im not even sure what that is. Its just an oem alternator from my local parts stop.

When it comes to the green wire, if i run it from something with power at ignition on and it fixes it, is there any reason i cant just leave it at that? Something tells me its going to be more something with the green wire than anything because of all the intermittent-ness. I also read somewhere last night that the gauge cluster is tied in to the green wire for the battery/alternator light and that even a faulty gauge could cause this issue
 

lwarrior1016

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Started it up today. Almost 70 degrees out. Charging just fine. I dont think it has a 3g alternator. Then again, im not even sure what that is. Its just an oem alternator from my local parts stop.

When it comes to the green wire, if i run it from something with power at ignition on and it fixes it, is there any reason i cant just leave it at that? Something tells me its going to be more something with the green wire than anything because of all the intermittent-ness. I also read somewhere last night that the gauge cluster is tied in to the green wire for the battery/alternator light and that even a faulty gauge could cause this issue
What year is your car?
 

lwarrior1016

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Ok, so looking at diagrams 5.0 and 4.6 have the same style wiring. If you put ignition voltage to the green wire, and the alternator works, you can absolutely leave it like that. But I don’t think the battery light will work anymore, the gauge should still work though.


A bad gauge or resistor will cause it not to charge. It breaks the circuit on the green wire that excites the alternator. I ran my 2v alternator with ignition power straight to that wire for years and had no issues.
 

tvsn95

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Check out some of my old threads,, I spent a ton and lost head gaskets in the process. I created a lot of problems for myself. It was bad Alt for the 3rd time. the regulators are just no good.
I now run the sensing wire to the red injector power in the harness. that gives the alt the max load as seen by the ECU. You can ground the regulator from the back and push it to full charge at any time. ( look at the writing on the back of regulator)
If you have a way to datalog the alt that will tell you everything
 

cobrajeff96

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I think you should get in contact with Mark Olson (Accutach). If anyone can navigate towards the culprit and the fix, it's him.
 

ttocs

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does your car beep at you for 10-15 secs every time you start it? If so its trying to tell you that a warning light is out, and we probably know which one. I would try replacing it just to keep everything stock prior to rerouting wiring.
 
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Stangswagalicious

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Ok, so looking at diagrams 5.0 and 4.6 have the same style wiring. If you put ignition voltage to the green wire, and the alternator works, you can absolutely leave it like that. But I don’t think the battery light will work anymore, the gauge should still work though.


A bad gauge or resistor will cause it not to charge. It breaks the circuit on the green wire that excites the alternator. I ran my 2v alternator with ignition power straight to that wire for years and had no issues.
Excellent. I may just do that. To me it seems like whatever it is causing this is related to the voltage regulator. If the field isnt getting power, then that explains a lot. Especially when theres either perfect charge or no charge at all. I just wish i knew why the outside temperature affects this so much… i hate being beaten by a car
 
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Stangswagalicious

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does your car beep at you for 10-15 secs every time you start it? If so its trying to tell you that a warning light is out, and we probably know which one. I would try replacing it just to keep everything stock prior to rerouting wiring.
No, the car does not beep. I believe iv even seen the battery light or alternator light come on when the charge gets REAL low
 

95opal

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No, the car does not beep. I believe iv even seen the battery light or alternator light come on when the charge gets REAL low

Anytime the alt stops charging the alt light on the dash should pop on. If it doesnt come on than either the bulb is beat or the green wire running to it has a break. Either way that light will tell you if its that circuit or the problem lies elsewhere.
 

KasperBPMC

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Sorry, didnt read many of these. Convert it to a 3g alternator and make it 1 wire to the battery. I think the 3g alternator are 135 amps. My two cents
 
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Stangswagalicious

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Ok guys heres the update. I never looked up a green wire tutorial, but i assumed it was just cutting the wire and hooking it up to a ignition on hot circuit. Well, i did just that and now every fuse under the hood stays hot weather the key is on or not. Wtf did i just do?

All i did was cut the wire by the pigtail close to the fuse box, covered the end of the wire attached to the pig tail, extended the wire goi g to the alternator and hooked it up to a fuse. Even if the wire is un plugged from the fuse box everything stays on. It killed the battery over night. Alternator works at least but thats no good if the car dies over night...
 

cobrajeff96

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Sounds like the new splice backfed the electrical system with a wire that is hot at all times. Could be lucky the splice (which by the sound of it is of a thinner gauge) didn't melt and start a fire on bare metal somewhere. Be careful.
 

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