Roasting the alternator?
10-03-2016, 09:40 AM
#41
Pro
Thread Starter
That's the increased drop in voltage as the current load goes up. That's is sort of to be expected.
The regulator should compensate, except if the voltage is getting dropped in the wires and connectors.
What rpm are you doing you voltage drop test at? Normally you don't do that at idle.
Print out your schematic, if you can get a current meter, set the rpm to (there should be a test spec like 2,000rpm, but I don't know what GM uses), measure branch currents, and then voltages, and mark the schematic, and you can calculate the power drop at all the drops.
Your big alt should be plenty big, but there could still be a bad wire or connector, and it doesn't show up as you're load testing in the driveway (I presume).
Oh, I have seen things, say it needs 1,000 watts to run. And it will get 1,000 watts at 10V 100A(even if that's 12V at the alternator) or it will get 78A at an actual 12.8V. The first case puts a huge load on the alternator or wire/connector.
The regulator should compensate, except if the voltage is getting dropped in the wires and connectors.
What rpm are you doing you voltage drop test at? Normally you don't do that at idle.
Print out your schematic, if you can get a current meter, set the rpm to (there should be a test spec like 2,000rpm, but I don't know what GM uses), measure branch currents, and then voltages, and mark the schematic, and you can calculate the power drop at all the drops.
Your big alt should be plenty big, but there could still be a bad wire or connector, and it doesn't show up as you're load testing in the driveway (I presume).
Oh, I have seen things, say it needs 1,000 watts to run. And it will get 1,000 watts at 10V 100A(even if that's 12V at the alternator) or it will get 78A at an actual 12.8V. The first case puts a huge load on the alternator or wire/connector.
But yes, I'm doing it at idle. This isn't a street car; I'm either idling or racing around the track, so I need the alternator to work at idle.
Already checked all my connections and they're good. Traced as much of the wire as I can and it's good as well, minus the foot or so behind the motor I can't get my hands on, but it's not showing a huge drop so I would imagine it's okay.
10-03-2016, 12:08 PM
#42
Burning Brakes
So, first problem is it might not supply the power you want at an idle. I get that's what you want, but first you need to figure out if your alternator is working right and that you need to idle up and test it's output.
If that's good, and at idle it doesn't work, then you need either to spin it faster, likely not an option, or a higher output alternator.
Or you can swap parts until it might work or you give up.
Light bulbs are a good example, their resistance is much lower when it's cold that when it's hot. So it draws more current until it warms up, if it never warms up enough, it will continue to draw more current.
Which if your alternator can't put that out, you get voltage drop. I think starters have the same behavior.
If that's good, and at idle it doesn't work, then you need either to spin it faster, likely not an option, or a higher output alternator.
Or you can swap parts until it might work or you give up.
Light bulbs are a good example, their resistance is much lower when it's cold that when it's hot. So it draws more current until it warms up, if it never warms up enough, it will continue to draw more current.
Which if your alternator can't put that out, you get voltage drop. I think starters have the same behavior.
Last edited by QKSLVRZ; 10-03-2016 at 12:09 PM.
10-03-2016, 02:01 PM
#43
Pro
Thread Starter
So, first problem is it might not supply the power you want at an idle. I get that's what you want, but first you need to figure out if your alternator is working right and that you need to idle up and test it's output.
If that's good, and at idle it doesn't work, then you need either to spin it faster, likely not an option, or a higher output alternator.
Or you can swap parts until it might work or you give up.
Light bulbs are a good example, their resistance is much lower when it's cold that when it's hot. So it draws more current until it warms up, if it never warms up enough, it will continue to draw more current.
Which if your alternator can't put that out, you get voltage drop. I think starters have the same behavior.
If that's good, and at idle it doesn't work, then you need either to spin it faster, likely not an option, or a higher output alternator.
Or you can swap parts until it might work or you give up.
Light bulbs are a good example, their resistance is much lower when it's cold that when it's hot. So it draws more current until it warms up, if it never warms up enough, it will continue to draw more current.
Which if your alternator can't put that out, you get voltage drop. I think starters have the same behavior.
That analogy is backwards. Alternators have their highest output when they're cold. They output less when they're hot.
And it's not that bulbs "draw" more current until they warm up, it's that the circuit with less resistance has a greater flow of electricity, i.e. current.
10-03-2016, 03:33 PM
#44
Burning Brakes
That analogy is backwards. Alternators have their highest output when they're cold. They output less when they're hot.
And it's not that bulbs "draw" more current until they warm up, it's that the circuit with less resistance has a greater flow of electricity, i.e. current.
And it's not that bulbs "draw" more current until they warm up, it's that the circuit with less resistance has a greater flow of electricity, i.e. current.
I was talking about a hot or cold light bulb as an example of a device that might draw more current if the alternator can not generate a high enough output voltage, compared to an alternator that can generate it's rated voltage. This aggravates the problem you're having. Now I know you don't have a big light bulb, but some amps, which might include ignition amps, sometimes have this. Not a problem with enough power.
I think you have to figure out how much load is on your alternator and how much current is it generating.
But it might not work at the rpm you're at if you have something weird going on.
BTW, I have 45 years of electronics.
10-03-2016, 04:33 PM
#45
Pro
Thread Starter
Not talking about a hot or cold alternator.
I was talking about a hot or cold light bulb as an example of a device that might draw more current if the alternator can not generate a high enough output voltage, compared to an alternator that can generate it's rated voltage.
I was talking about a hot or cold light bulb as an example of a device that might draw more current if the alternator can not generate a high enough output voltage, compared to an alternator that can generate it's rated voltage.
Not trying to argue with your experience, only understand what you're trying to say. I'm an engineer myself so I like to have things very well laid out and explained properly. Usually that means challenging what people say so they have the opportunity to explain it a little different. Just trying to understand what you're getting at.
All that said, it still doesn't explain why the alternator would produce a lower voltage with a higher load. I get that some things with fixed power consumption draw more current at lower voltages, but that doesn't explain why the lower voltages are there in the first place. Even if the load was greater than the alternator output, I wouldn't expect the alternator to decrease output.
10-03-2016, 04:41 PM
#46
Safety Car
So you're talking about a device with a set power requirement drawing more current at lower voltage than at higher voltage. Got it.
Ignition amps? Like current used in the ignition system?
Right, I get that the alternator is going to output less at a lower RPM. That's not the problem I'm having.
Not trying to argue with your experience, only understand what you're trying to say. I'm an engineer myself so I like to have things very well laid out and explained properly. Usually that means challenging what people say so they have the opportunity to explain it a little different. Just trying to understand what you're getting at.
All that said, it still doesn't explain why the alternator would produce a lower voltage with a higher load. I get that some things with fixed power consumption draw more current at lower voltages, but that doesn't explain why the lower voltages are there in the first place. Even if the load was greater than the alternator output, I wouldn't expect the alternator to decrease output.
Ignition amps? Like current used in the ignition system?
Right, I get that the alternator is going to output less at a lower RPM. That's not the problem I'm having.
Not trying to argue with your experience, only understand what you're trying to say. I'm an engineer myself so I like to have things very well laid out and explained properly. Usually that means challenging what people say so they have the opportunity to explain it a little different. Just trying to understand what you're getting at.
All that said, it still doesn't explain why the alternator would produce a lower voltage with a higher load. I get that some things with fixed power consumption draw more current at lower voltages, but that doesn't explain why the lower voltages are there in the first place. Even if the load was greater than the alternator output, I wouldn't expect the alternator to decrease output.
10-04-2016, 09:45 AM
#47
Burning Brakes
Yes, ignition amps would be one I would suspect.
but I still think you're dismissing rpm, and I get that your interest is supplying the power for idle, but IMO you still need to tell if the alternator is failing specifications, or it meets spec's and it just isn't big enough.
The confounding factor is if the car is basically stock (electronics wise), it should be enough to power the car at idle.
But without more specific (like currents), it will be hard to tell what's wrong.
And I get you don't know me from Adam, that's why I replied as I did, I am at least competent
but I still think you're dismissing rpm, and I get that your interest is supplying the power for idle, but IMO you still need to tell if the alternator is failing specifications, or it meets spec's and it just isn't big enough.
The confounding factor is if the car is basically stock (electronics wise), it should be enough to power the car at idle.
But without more specific (like currents), it will be hard to tell what's wrong.
And I get you don't know me from Adam, that's why I replied as I did, I am at least competent
10-04-2016, 09:47 AM
#48
Burning Brakes
All that said, it still doesn't explain why the alternator would produce a lower voltage with a higher load. I get that some things with fixed power consumption draw more current at lower voltages, but that doesn't explain why the lower voltages are there in the first place. Even if the load was greater than the alternator output, I wouldn't expect the alternator to decrease output.
10-04-2016, 04:20 PM
#49
Pro
Thread Starter
Yes, ignition amps would be one I would suspect.
but I still think you're dismissing rpm, and I get that your interest is supplying the power for idle, but IMO you still need to tell if the alternator is failing specifications, or it meets spec's and it just isn't big enough.
The confounding factor is if the car is basically stock (electronics wise), it should be enough to power the car at idle.
But without more specific (like currents), it will be hard to tell what's wrong.
And I get you don't know me from Adam, that's why I replied as I did, I am at least competent
but I still think you're dismissing rpm, and I get that your interest is supplying the power for idle, but IMO you still need to tell if the alternator is failing specifications, or it meets spec's and it just isn't big enough.
The confounding factor is if the car is basically stock (electronics wise), it should be enough to power the car at idle.
But without more specific (like currents), it will be hard to tell what's wrong.
And I get you don't know me from Adam, that's why I replied as I did, I am at least competent
The alternator has a max power output of P.
Since power=voltage*current, as the current requirement goes above what the alternator can supply, the voltage drops, since the power is at a fixed maximum.
As the voltage in the system drops, the current requirement for a fixed power requirement is increased, thus exacerbating the problem.
That sound right?
10-04-2016, 06:18 PM
#50
Safety Car
So you're talking about a device with a set power requirement drawing more current at lower voltage than at higher voltage. Got it.
Ignition amps? Like current used in the ignition system?
Right, I get that the alternator is going to output less at a lower RPM. That's not the problem I'm having.
Not trying to argue with your experience, only understand what you're trying to say. I'm an engineer myself so I like to have things very well laid out and explained properly. Usually that means challenging what people say so they have the opportunity to explain it a little different. Just trying to understand what you're getting at.
All that said, it still doesn't explain why the alternator would produce a lower voltage with a higher load. I get that some things with fixed power consumption draw more current at lower voltages, but that doesn't explain why the lower voltages are there in the first place. Even if the load was greater than the alternator output, I wouldn't expect the alternator to decrease output.
Ignition amps? Like current used in the ignition system?
Right, I get that the alternator is going to output less at a lower RPM. That's not the problem I'm having.
Not trying to argue with your experience, only understand what you're trying to say. I'm an engineer myself so I like to have things very well laid out and explained properly. Usually that means challenging what people say so they have the opportunity to explain it a little different. Just trying to understand what you're getting at.
All that said, it still doesn't explain why the alternator would produce a lower voltage with a higher load. I get that some things with fixed power consumption draw more current at lower voltages, but that doesn't explain why the lower voltages are there in the first place. Even if the load was greater than the alternator output, I wouldn't expect the alternator to decrease output.
So basically here's what you're saying:
The alternator has a max power output of P.
Since power=voltage*current, as the current requirement goes above what the alternator can supply, the voltage drops, since the power is at a fixed maximum.
As the voltage in the system drops, the current requirement for a fixed power requirement is increased, thus exacerbating the problem.
That sound right?
The alternator has a max power output of P.
Since power=voltage*current, as the current requirement goes above what the alternator can supply, the voltage drops, since the power is at a fixed maximum.
As the voltage in the system drops, the current requirement for a fixed power requirement is increased, thus exacerbating the problem.
That sound right?
10-04-2016, 07:05 PM
#51
Pro
Thread Starter
10-05-2016, 02:34 PM
#52
Burning Brakes
Yep.
And that's why I suggest you figure out if your alternator is meeting whatever it's design spec is. BTW, with alternators, the faster it spins, the more power it can produce (excluding any regulation applied).
If it meets spec, and you don't have some other problem (why you need to get currents and voltages)you have to get something that meets your spec. If it doesn't, then you need to get a new one, and it sounds like you have and they go bad, which sounds like it's just over loaded.
For the alternator to make maximum output, the rotor gets the maximum current. If they work at first, and then "fade" an increase in the rotor's circuit wiring resistance (could be anything, not just the wires) would reduce output power.
Though it might be hard to get into one and measure to see if it's failed. But if you end up with one that's "bad" see if you can see what happened inside, if you want of course.
And that's why I suggest you figure out if your alternator is meeting whatever it's design spec is. BTW, with alternators, the faster it spins, the more power it can produce (excluding any regulation applied).
If it meets spec, and you don't have some other problem (why you need to get currents and voltages)you have to get something that meets your spec. If it doesn't, then you need to get a new one, and it sounds like you have and they go bad, which sounds like it's just over loaded.
For the alternator to make maximum output, the rotor gets the maximum current. If they work at first, and then "fade" an increase in the rotor's circuit wiring resistance (could be anything, not just the wires) would reduce output power.
Though it might be hard to get into one and measure to see if it's failed. But if you end up with one that's "bad" see if you can see what happened inside, if you want of course.
10-05-2016, 02:38 PM
#53
Pro
Thread Starter
Yep.
And that's why I suggest you figure out if your alternator is meeting whatever it's design spec is. BTW, with alternators, the faster it spins, the more power it can produce (excluding any regulation applied).
If it meets spec, and you don't have some other problem (why you need to get currents and voltages)you have to get something that meets your spec. If it doesn't, then you need to get a new one, and it sounds like you have and they go bad, which sounds like it's just over loaded.
For the alternator to make maximum output, the rotor gets the maximum current. If they work at first, and then "fade" an increase in the rotor's circuit wiring resistance (could be anything, not just the wires) would reduce output power.
Though it might be hard to get into one and measure to see if it's failed. But if you end up with one that's "bad" see if you can see what happened inside, if you want of course.
And that's why I suggest you figure out if your alternator is meeting whatever it's design spec is. BTW, with alternators, the faster it spins, the more power it can produce (excluding any regulation applied).
If it meets spec, and you don't have some other problem (why you need to get currents and voltages)you have to get something that meets your spec. If it doesn't, then you need to get a new one, and it sounds like you have and they go bad, which sounds like it's just over loaded.
For the alternator to make maximum output, the rotor gets the maximum current. If they work at first, and then "fade" an increase in the rotor's circuit wiring resistance (could be anything, not just the wires) would reduce output power.
Though it might be hard to get into one and measure to see if it's failed. But if you end up with one that's "bad" see if you can see what happened inside, if you want of course.
I've had them tested and tried several different ones. I've not actually run the spec test, but statistically six different alternators aren't all going to fail in the same manner on the same car. I used to work for an alternator remanufacturer and that sort of situation means there's a common denominator lol.
We'll see how the MechMan unit does. Hopefully it'll fix my problem.
10-05-2016, 04:48 PM
#54
Burning Brakes
Ha, sometimes I'm good
http://www.mechman.com/color-catalog-pdf/
10-05-2016, 05:04 PM
#55
Pro
Thread Starter
They should have a output power curve?
Ha, sometimes I'm good
http://www.mechman.com/color-catalog-pdf/
Ha, sometimes I'm good
http://www.mechman.com/color-catalog-pdf/
10-10-2016, 09:04 AM
#57
Drifting
I had the same type of intermittent issue on my 2006 C6 when the temp was hot.
I upgraded all my wiring to 1/0 guage wire on the "big 3", battery to alternator, battery to engine block (i used an aluminum bolt here on the block since aluminum has much less electrical resistance, I think I just used one of the bolts from the mounting bracket of my Oil Catch Can), battery to frame.
No issues since then. Stock OEM alternator. It would drop to low 12's in volts or even high 11's....I haven't seen it go below 13 volts ever since the upgrade.
I upgraded all my wiring to 1/0 guage wire on the "big 3", battery to alternator, battery to engine block (i used an aluminum bolt here on the block since aluminum has much less electrical resistance, I think I just used one of the bolts from the mounting bracket of my Oil Catch Can), battery to frame.
No issues since then. Stock OEM alternator. It would drop to low 12's in volts or even high 11's....I haven't seen it go below 13 volts ever since the upgrade.
Last edited by bdanyluk; 10-10-2016 at 09:06 AM.
10-10-2016, 10:17 AM
#58
Pro
Thread Starter
I had the same type of intermittent issue on my 2006 C6 when the temp was hot.
I upgraded all my wiring to 1/0 guage wire on the "big 3", battery to alternator, battery to engine block (i used an aluminum bolt here on the block since aluminum has much less electrical resistance, I think I just used one of the bolts from the mounting bracket of my Oil Catch Can), battery to frame.
No issues since then. Stock OEM alternator. It would drop to low 12's in volts or even high 11's....I haven't seen it go below 13 volts ever since the upgrade.
I upgraded all my wiring to 1/0 guage wire on the "big 3", battery to alternator, battery to engine block (i used an aluminum bolt here on the block since aluminum has much less electrical resistance, I think I just used one of the bolts from the mounting bracket of my Oil Catch Can), battery to frame.
No issues since then. Stock OEM alternator. It would drop to low 12's in volts or even high 11's....I haven't seen it go below 13 volts ever since the upgrade.
10-10-2016, 08:20 PM
#59
Melting Slicks
OK....here's a thought....
Is your alternator OEM? I had an alternator fail at a hot autocross event a few years back. A buddy helped me change it out while still at the event with some auto parts store refurb to get me home. It worked but didn't really charge the battery at idle (a problem if you're in one of those long autocross lines waiting your turn to run). I took it back and replaced it with another auto parts store unit. Same basic issue.....not quite enough at idle to charge the battery. Both of those units tested "OK" by the store....didn't work on my car though.
I decided to look for an OEM replacement and saw one on Amazon (for basically the same prices as the auto parts store specials) and put that it. Problem solved...for over a year now. Note: the auto parts store units looked exactly like the OEM....but were labeled as refurbished...and definitely didn't do the job properly.
I know you know how to change your alternator, but the symptom to the problem is displayed at the start of this video (sounds a lot like your symptom)....and the result after putting a new OEM unit is near the end (skip ahead to 11:35 mark).
Good luck!
Is your alternator OEM? I had an alternator fail at a hot autocross event a few years back. A buddy helped me change it out while still at the event with some auto parts store refurb to get me home. It worked but didn't really charge the battery at idle (a problem if you're in one of those long autocross lines waiting your turn to run). I took it back and replaced it with another auto parts store unit. Same basic issue.....not quite enough at idle to charge the battery. Both of those units tested "OK" by the store....didn't work on my car though.
I decided to look for an OEM replacement and saw one on Amazon (for basically the same prices as the auto parts store specials) and put that it. Problem solved...for over a year now. Note: the auto parts store units looked exactly like the OEM....but were labeled as refurbished...and definitely didn't do the job properly.
I know you know how to change your alternator, but the symptom to the problem is displayed at the start of this video (sounds a lot like your symptom)....and the result after putting a new OEM unit is near the end (skip ahead to 11:35 mark).
Good luck!
Last edited by DigitalWidgets; 10-10-2016 at 08:22 PM.
10-11-2016, 08:31 AM
#60
Pro
Thread Starter
OK....here's a thought....
Is your alternator OEM? I had an alternator fail at a hot autocross event a few years back. A buddy helped me change it out while still at the event with some auto parts store refurb to get me home. It worked but didn't really charge the battery at idle (a problem if you're in one of those long autocross lines waiting your turn to run). I took it back and replaced it with another auto parts store unit. Same basic issue.....not quite enough at idle to charge the battery. Both of those units tested "OK" by the store....didn't work on my car though.
I decided to look for an OEM replacement and saw one on Amazon (for basically the same prices as the auto parts store specials) and put that it. Problem solved...for over a year now. Note: the auto parts store units looked exactly like the OEM....but were labeled as refurbished...and definitely didn't do the job properly.
I know you know how to change your alternator, but the symptom to the problem is displayed at the start of this video (sounds a lot like your symptom)....and the result after putting a new OEM unit is near the end (skip ahead to 11:35 mark).
https://www.youtube.com/watch?v=BkAvjGYDkf8
Good luck!
Is your alternator OEM? I had an alternator fail at a hot autocross event a few years back. A buddy helped me change it out while still at the event with some auto parts store refurb to get me home. It worked but didn't really charge the battery at idle (a problem if you're in one of those long autocross lines waiting your turn to run). I took it back and replaced it with another auto parts store unit. Same basic issue.....not quite enough at idle to charge the battery. Both of those units tested "OK" by the store....didn't work on my car though.
I decided to look for an OEM replacement and saw one on Amazon (for basically the same prices as the auto parts store specials) and put that it. Problem solved...for over a year now. Note: the auto parts store units looked exactly like the OEM....but were labeled as refurbished...and definitely didn't do the job properly.
I know you know how to change your alternator, but the symptom to the problem is displayed at the start of this video (sounds a lot like your symptom)....and the result after putting a new OEM unit is near the end (skip ahead to 11:35 mark).
https://www.youtube.com/watch?v=BkAvjGYDkf8
Good luck!
There's a big difference between refurbished and remanufactured. I'm not sure if you meant to say refurbished, but essentially that's a used alternator that passes the test. A remanufactured one is where it's stripped down to it's parts, most of the electronics are replaced, and then everything has to pass inspection on a component level.
Not saying it isn't possible. You could have had one of the other companies. Remy is the best in the aftermarket, so anything else I can't speak for.
The aftermarket unit I have is a Remy though, and I've tested my car with a known good OEM alternator with the exact same results.