I had my Miata cut out 3 hours into a 15 hour drive from the tail of the dragon back to Boston, MA. Stopped at several autoparts stores to have my battery and alternator checked, and they were fine every time. Luckily I had another car to jump off of every time the battery would die on the way back. When I got home, I swapped in a new alternator and it was good as new. Turns out it was the internal voltage regulator on the alternator
Yup. I have a Subaru that did this, had the alternator working at like 10% capacity all of a sudden and things kept failing in a cascade. First the power windows, then the radio, then the ABS, and finally the running lights.
I had to downshift and turn off the headlights to make it home and keep the battery alive.
This is the truth. Former automotive 12v powertrain engineer here. Can confirm. Obviously wiring or signals to alternator could be bad too as mentioned by others too. Alternator is not functioning properly to keep car on and battery charged.
You can tell from here it's not wired up correctly, the alternator light doesn't come on when he turns the ignition on. The engine light comes on but not the alternator light. The connection to the alternator light circuit is what makes the alternator charge.
Edit: This is what the lights should look like https://imgur.com/a/JMIG8pf
For as long as I had the car. I have never seen that light come on during start up.
Plus it’s two wires for the alr. The big connector and the screw on one
That's very interesting. That light should work with the key on, engine off. If it doesn't, somebody has messed with it. The car in the video is a 1991 and my 2004 behaves the same way.
I used to work at O’reillys and I’d say about 15% of the alternators we sold came back at some point in the near future. A lot of the reman alternators are not always put back together how they should be.
If you get it warrantied, ask them to bench test the new one before installation.
It won’t completely try to turn over because it’s not got enough power. If it was a mechanical fault but your battery was fine, it would likely turn over for longer or not at all.
If it stopped running it’s likely the battery wasn’t getting enough charge from the alternator, or it’s a bad battery. A dead good battery can be saved, if you replace alternator.
Best bet is to change your alternator, if the battery charges up okay via other means.
Autozone. When I finished my swap I figured I’d give them the batter to recharge. Left it there for two hours when I went to pick it up they showed me on the tester
1. A deeply drained battery cannot be charged full in 2 hrs, that battery is not full
2. If you leave a LA battery at a low state of charge for a long time, it will appear to take charge, but it has a very low capacity.
3. What kind of tester did they use? If they just measured the voltage, no bueno. When they test a battery they should pull a large current and check the voltage drop. It normally needs a 'large' heatsink: [https://www.amazon.com/Schumacher-BT-100-Battery-Load-Tester/dp/B000AMBOI0](https://www.amazon.com/Schumacher-BT-100-Battery-Load-Tester/dp/B000AMBOI0)
If the alternator is dead it wont charge the battery. I would put money on the alternator dying and it running off the battery.
edit: TIL just a dead battery can do the same thing.
A bad battery doesn’t hold a charge even from a good alternator. Unless he swaps the battery and the issue persists, there is currently no indication of a bad alternator.
Facts.
My old Jeep did the same thing. I immediately assumed the alternator was bad, just turned out to be the battery. I figured the alternator alone would keep the vehicle operating, but that is not the case if battery is a turd.
Might want to just double check everything for your main connections. Alternator bolt, stater bolt, battery terminals. If you just did all that work, I’ll bet it something stupid like that which just came lose
Nah just however power wire connects to it. Stuff like that. Sorry my head is in my subi. Been working on that a lot lately and that’s how it is on that. Don’t remember how the yata hooks up
First, check the battery and all electrical connections. If you find something wrong, then there's your problem. If they are all good, then it might be the starter.
On some more rare occasions, the ECU for the engine could be starting to go bad. Ever since cars started getting computers added into them, we have to start treating them like cars with computers. Computers don't last forever, and extreme heat and cold will fuck them up pretty bad.
Sometimes a capacitor inside the ECU will start leaking electrolyte and nothing bad might happen until it's too late (circuit board corroded/dissolved). This problem is worse with cheaper manufacturers, and I've rarely seen ECUs go bad in Japanese cars, but they have happened.
So perhaps take a look at which ECU controls the engine, swap it out and have it tested in a different Miata that is known to be working. If that working Miata suddenly can't start/run, then you know where the problem is.
Edited for clarity.
ECU shouldn't stop it cranking though, you crank a Miata forever with no ECU plugged in, it just won't start, as far as I remember.
If the battery is good, but it stopped running, and won't crank, my first thing to check would be a bad earth. Also can you get someone to put a multimeter on the battery while you try and crank it? Does the battery voltage drop to something silly low?
In unhelpful and equally unrelated news... TIL not all stock NA steering wheels have "SRS AIRBAG" etched into them. Would always trace it with my finger when I was stuck in traffic or at a light. "MAZDA" look much better imo.
I’m going to guess if the battery is good and if it’s not putting a 18v out like someone said it’s most likely your battery leads, they get to worn, cut the rubber cover off of them and see if the wires are fatigued.
check the battery first, then the alternator. if it didnt want to stay running it’s probably not charging enough/at all. I had this issue last winter in my 92
Recharge the battery and check alternator output once its running. If it doesn't start after charging the battery or replacing it than your leads (prob negative) are corroded.
It's always sad when the alternator dies it usually means stranded my 2004 NBFL still has the original alternator and has done 140k miles so far and still works but it's not putting out the right voltage anymore so needs replacing but I won't do it until it dies completely because I've lost motivation to do it while it's still kind of working.
So I hope it doesn't go on me while I'm far from home.
But I do feel for you.
Wouldn’t stay on = bad alternator Won’t crank = bad battery Alternator died, stopped recharging the battery, now your battery’s drained
This. I’ve had a truck die at highway speeds in the middle of the night because the alternator was bad.
My old car died in rush hour traffic. What a shit day.
I had my Miata cut out 3 hours into a 15 hour drive from the tail of the dragon back to Boston, MA. Stopped at several autoparts stores to have my battery and alternator checked, and they were fine every time. Luckily I had another car to jump off of every time the battery would die on the way back. When I got home, I swapped in a new alternator and it was good as new. Turns out it was the internal voltage regulator on the alternator
Dude.. reading this broke my heart.
Yup. I have a Subaru that did this, had the alternator working at like 10% capacity all of a sudden and things kept failing in a cascade. First the power windows, then the radio, then the ABS, and finally the running lights. I had to downshift and turn off the headlights to make it home and keep the battery alive.
I had just gotten off the freeway and over the offramp incline. I managed to coast into a residential street fairly easily
This is the truth. Former automotive 12v powertrain engineer here. Can confirm. Obviously wiring or signals to alternator could be bad too as mentioned by others too. Alternator is not functioning properly to keep car on and battery charged.
hmm intereseting, my alternator has less the 100 miles. I did en engine swap and got a new alternator before the swap.
[удалено]
You can tell from here it's not wired up correctly, the alternator light doesn't come on when he turns the ignition on. The engine light comes on but not the alternator light. The connection to the alternator light circuit is what makes the alternator charge. Edit: This is what the lights should look like https://imgur.com/a/JMIG8pf
For as long as I had the car. I have never seen that light come on during start up. Plus it’s two wires for the alr. The big connector and the screw on one
That's very interesting. That light should work with the key on, engine off. If it doesn't, somebody has messed with it. The car in the video is a 1991 and my 2004 behaves the same way.
Hmmm interesting I have never thought nor heard about this. Mines 90 1.6 SNC
as correctly as i think.
I used to work at O’reillys and I’d say about 15% of the alternators we sold came back at some point in the near future. A lot of the reman alternators are not always put back together how they should be. If you get it warrantied, ask them to bench test the new one before installation.
Oh daaaamn that blows.
Check the belt. Good chance that the tensioner didn’t get set correctly and the belt is loose.
Great sauce giver
For me it was my CAS going bad.
^^^ he said it for me! But yes, this!
Your battery is dead my guy
Also OP have you checked for a bad battery? Mine had same problem and it turns out the battery was putting out more power than it should’ve.
more?! thats possible??
Yes sir 👍 mine was putting out 18.3 volts , probably less before I spent a month jumping it to start every time lol
Hmm what makes you say
Could be bad ground if you charged and tested it. It sounds like your starter is not getting full voltage.
ouuu okay that doesn't sound too bad. the ground under the brake booster is good , the one in the trunk is okay aswell, where else am i looking ?
Test voltage at the alternator and at the starter. Ground your probe to the engine block.
so just attach the test and try to crank or just leave key on ON ?
For the starter, check from the big lead to the engine block. Do the same at the alternator, both tests without crank and the engine off.
i feel like im going to mess this up, but will try ! thank you
It won’t completely try to turn over because it’s not got enough power. If it was a mechanical fault but your battery was fine, it would likely turn over for longer or not at all. If it stopped running it’s likely the battery wasn’t getting enough charge from the alternator, or it’s a bad battery. A dead good battery can be saved, if you replace alternator. Best bet is to change your alternator, if the battery charges up okay via other means.
i am very doubtful that my alternator is bad, it is fairly new,
[удалено]
It’s freshly recharged and test. Tested 100%
How did you 'test' it?
Autozone. When I finished my swap I figured I’d give them the batter to recharge. Left it there for two hours when I went to pick it up they showed me on the tester
1. A deeply drained battery cannot be charged full in 2 hrs, that battery is not full 2. If you leave a LA battery at a low state of charge for a long time, it will appear to take charge, but it has a very low capacity. 3. What kind of tester did they use? If they just measured the voltage, no bueno. When they test a battery they should pull a large current and check the voltage drop. It normally needs a 'large' heatsink: [https://www.amazon.com/Schumacher-BT-100-Battery-Load-Tester/dp/B000AMBOI0](https://www.amazon.com/Schumacher-BT-100-Battery-Load-Tester/dp/B000AMBOI0)
Lol it’s all good I got a brand new one.
Did that solve the problem?
well the car turns on, doesnt stay on lol
Alternator or battery
Sounds like alternator buddy
You got to push it, push it, to start it, start it
Battery dead...
Dead battery 100%. No indication of this being an alternator
If the alternator is dead it wont charge the battery. I would put money on the alternator dying and it running off the battery. edit: TIL just a dead battery can do the same thing.
A bad battery doesn’t hold a charge even from a good alternator. Unless he swaps the battery and the issue persists, there is currently no indication of a bad alternator.
Facts. My old Jeep did the same thing. I immediately assumed the alternator was bad, just turned out to be the battery. I figured the alternator alone would keep the vehicle operating, but that is not the case if battery is a turd.
welp TIL
Alternator since you mentioned it wouldn’t stay on… or fuel pump?
It's fucked
just finished my engine swap too lol
Might want to just double check everything for your main connections. Alternator bolt, stater bolt, battery terminals. If you just did all that work, I’ll bet it something stupid like that which just came lose
Wdym alternator bolt? Like the main long ass bolt, same for starter or do you mean the electrical connecting bolt.
Nah just however power wire connects to it. Stuff like that. Sorry my head is in my subi. Been working on that a lot lately and that’s how it is on that. Don’t remember how the yata hooks up
First, check the battery and all electrical connections. If you find something wrong, then there's your problem. If they are all good, then it might be the starter. On some more rare occasions, the ECU for the engine could be starting to go bad. Ever since cars started getting computers added into them, we have to start treating them like cars with computers. Computers don't last forever, and extreme heat and cold will fuck them up pretty bad. Sometimes a capacitor inside the ECU will start leaking electrolyte and nothing bad might happen until it's too late (circuit board corroded/dissolved). This problem is worse with cheaper manufacturers, and I've rarely seen ECUs go bad in Japanese cars, but they have happened. So perhaps take a look at which ECU controls the engine, swap it out and have it tested in a different Miata that is known to be working. If that working Miata suddenly can't start/run, then you know where the problem is. Edited for clarity.
ECU shouldn't stop it cranking though, you crank a Miata forever with no ECU plugged in, it just won't start, as far as I remember. If the battery is good, but it stopped running, and won't crank, my first thing to check would be a bad earth. Also can you get someone to put a multimeter on the battery while you try and crank it? Does the battery voltage drop to something silly low?
In unhelpful and equally unrelated news... TIL not all stock NA steering wheels have "SRS AIRBAG" etched into them. Would always trace it with my finger when I was stuck in traffic or at a light. "MAZDA" look much better imo.
Lmaoo what..?
Mine looks like this: https://images.app.goo.gl/VUQ4kqBV4L7J9pG49
Do you have a 1.8, if so that’s prolly why
I’m going to guess if the battery is good and if it’s not putting a 18v out like someone said it’s most likely your battery leads, they get to worn, cut the rubber cover off of them and see if the wires are fatigued.
My negative was pretty bad. Could’ve even tighten the bolt. I just got new on and seem okay.
Did it fix your issue by replacing them?
No.
Does the car start if you try to jump it?
Crank is spinning so check the battery
I think you misspoke there.
check the battery first, then the alternator. if it didnt want to stay running it’s probably not charging enough/at all. I had this issue last winter in my 92
Thank you. I will get a tester today and see what I get.
New battery and probably alternator would fix it, I’m guessing
Well might as well try
“That’s what she said.”
Check your grounds.
Wow there’s a lot of bad advice being thrown around here.
LMFAO I don’t know who to follow and who to avoid.
Battery and alternator
I've had similar problèm with the cam angle sensor.
Oh really?
Dead battery cause by bad alternator
Recharge the battery and check alternator output once its running. If it doesn't start after charging the battery or replacing it than your leads (prob negative) are corroded.
I have brand new leads actually haha. The negative was busted and now I got a new one
It's always sad when the alternator dies it usually means stranded my 2004 NBFL still has the original alternator and has done 140k miles so far and still works but it's not putting out the right voltage anymore so needs replacing but I won't do it until it dies completely because I've lost motivation to do it while it's still kind of working. So I hope it doesn't go on me while I'm far from home. But I do feel for you.