Alternator?
01-09-2013, 05:35 PM
#1
2nd Gear Member
Thread Starter
Join Date: Sep 2009
Location: Jax FL
Posts: 442
Alternator?
OK. I have a P0340 code. I pulled the CMP and did a check I found somewhere and it appeared that it was bad, and as it was only $20 went ahead and replaced it. Reset the computer and drove it for several drive cycles, and the CEL came back with a P0340 again. I did some more research online and saw the plethora of posts referring to the alternator being a common cause of this. In amongst these was a way to check the alternator by hooking a DVOM across the alt circuit and checking for AC voltage. Well, I am getting just shy of 30Vac which makes me think it could be the alternator (or more technically the regulator, but as that is part of the alternator...).
I really don't have the money to be spending on this car right now, so first off, does my hypothesis sound correct, or am I more than likely barking up a wrong tree here? If it could be the alternator, where and what brand that is on the inexpensive side should I be looking at? The Motorcraft ones seem to be going for about $200... which I will spend if I have to, but don't really want to... but there are others that are around $100 also. Are those CHEAP (and not worth getting), or reasonably inexpensive?
Thank you.
James
I really don't have the money to be spending on this car right now, so first off, does my hypothesis sound correct, or am I more than likely barking up a wrong tree here? If it could be the alternator, where and what brand that is on the inexpensive side should I be looking at? The Motorcraft ones seem to be going for about $200... which I will spend if I have to, but don't really want to... but there are others that are around $100 also. Are those CHEAP (and not worth getting), or reasonably inexpensive?
Thank you.
James
01-09-2013, 08:00 PM
#2
5th Gear Member
Join Date: Jun 2006
Location: NY
Posts: 2,307
I went thru this last year. Aftermarket replacement stuck me after only 6 months. Eventually went to OEM. Save yourself the headache & extra expense of doing it more than once go MotoCraft replacement.
Ive changed my alt so many times I an do it in the dark w/ a Leatherman tool & a beer.
Ive changed my alt so many times I an do it in the dark w/ a Leatherman tool & a beer.
01-10-2013, 08:14 AM
#3
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
To get very technical the assembly is a generator, as it produces DC power; alternators produce AC power. Inside the generator is an alternator, rectifiers and a voltage regulator, but put all together it is a generator. Ford calls it a generator in the shop manualš, as do the shop manuals for most vehicles including modern motorcycles.
That aside, I have never measured the AC component of the generator's output on our cars with a multimeter, though I have with oscilloscopes and have never observed AC voltage of that magnitude--typically just 100 to 200 mV. Here is a typical trace:
You can see the AC component at 160 mV pk-pk. The frequency of the AC component shown here is 72 Hz or so, three times the generator rps (the alternator inside the generator is 3 phase) which with the Steeda UDPs on my car is twice the crankshaft rps.
72 / 3 = 24 rps at the generator shaft;
24 / 2 = 12 rps at the crankshaft;
12 * 60 = 720 rpm;
This frequency is low enough that nearly any multimeter should not have trouble providing an accurate reading, so I suspect your generator is bad.
A shorted or open rectifier would cause significant spikes in the generator output, easily visible on a 'scope--that is likely what your meter is averaging out and displaying.
As to where to buy, I would not hesitate to purchase a new generator from a FLAPS. They usually carry a lifetime warranty, and in 40+ years I have never purchased a bad one. I would avoid a $100 rebuilt, as for $100 out-the-door they did not rebuild much...
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š - At one time, way back when the rectifiers and regulator were external to the device driven by the engine, that device was an alternator--but that was a long time ago.
from the 2003 shop manual:
Print that out and bring it with you to the parts store--messes with their minds every time.
Oddly what are commonly called generators, those things used at construction sites and when camping, are most often actually alternators--go figure...
That aside, I have never measured the AC component of the generator's output on our cars with a multimeter, though I have with oscilloscopes and have never observed AC voltage of that magnitude--typically just 100 to 200 mV. Here is a typical trace:
You can see the AC component at 160 mV pk-pk. The frequency of the AC component shown here is 72 Hz or so, three times the generator rps (the alternator inside the generator is 3 phase) which with the Steeda UDPs on my car is twice the crankshaft rps.
72 / 3 = 24 rps at the generator shaft;
24 / 2 = 12 rps at the crankshaft;
12 * 60 = 720 rpm;
This frequency is low enough that nearly any multimeter should not have trouble providing an accurate reading, so I suspect your generator is bad.
A shorted or open rectifier would cause significant spikes in the generator output, easily visible on a 'scope--that is likely what your meter is averaging out and displaying.
As to where to buy, I would not hesitate to purchase a new generator from a FLAPS. They usually carry a lifetime warranty, and in 40+ years I have never purchased a bad one. I would avoid a $100 rebuilt, as for $100 out-the-door they did not rebuild much...
------------------------------------------------------
š - At one time, way back when the rectifiers and regulator were external to the device driven by the engine, that device was an alternator--but that was a long time ago.
from the 2003 shop manual:
Print that out and bring it with you to the parts store--messes with their minds every time.
Oddly what are commonly called generators, those things used at construction sites and when camping, are most often actually alternators--go figure...
01-10-2013, 12:06 PM
#5
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
With sales the revenue account is the source or the funds, and cash is application of the funds.
With expenses cash is the source of the funds, and the expenditure account is the application.
Using clearing accounts such as receivables and payables complicates it a bit, however you still credit the source and debit the application:
01-10-2013, 04:22 PM
#7
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
It made me nuts many years ago until I dated an accountant (I'm an ME) and she gave me the "credit the source of the funds/debit the application of the funds" clue. You have to eliminate in your mind the notion that + and - having anything to do with credit and debit...
01-10-2013, 06:13 PM
#8
2nd Gear Member
Thread Starter
Join Date: Sep 2009
Location: Jax FL
Posts: 442
I know I started the 'technically speaking' bit. Most people don't know the difference between a 'motor' and an 'engine'; and use the terms interchangeably (and to the average person, they are the same). I took my share of accounting classes in high school and college, so I do know the basic difference between credit and debit, but I don't use them in my everyday life so I would have to think about it before answering if somebody were to ask me now.
The few times I have bought alternators (generators, whatever lol) in the past for other vehicles, I have never hesitated to buy one from a FLAPS. In the worst case, they usually have warranties on them, so if something were to happen, I would just have to be in a position that I can pull the bad one and take it in to get a new one.
The few times I have bought alternators (generators, whatever lol) in the past for other vehicles, I have never hesitated to buy one from a FLAPS. In the worst case, they usually have warranties on them, so if something were to happen, I would just have to be in a position that I can pull the bad one and take it in to get a new one.
01-10-2013, 06:23 PM
#9
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
I know I started the 'technically speaking' bit. Most people don't know the difference between a 'motor' and an 'engine'; and use the terms interchangeably (and to the average person, they are the same). I took my share of accounting classes in high school and college, so I do know the basic difference between credit and debit, but I don't use them in my everyday life so I would have to think about it before answering if somebody were to ask me now.
The few times I have bought alternators (generators, whatever lol) in the past for other vehicles, I have never hesitated to buy one from a FLAPS. In the worst case, they usually have warranties on them, so if something were to happen, I would just have to be in a position that I can pull the bad one and take it in to get a new one.
01-10-2013, 07:32 PM
#10
2nd Gear Member
Thread Starter
Join Date: Sep 2009
Location: Jax FL
Posts: 442
OK, now I am in a quandary... I can get a Duralast (AutoZone) for $207 + tax + $32 core... I can get a Motorcraft for $215 + $60 core... or I can get a PA Performance for $260 (no core).
The only advantage to getting the AZ one is I can have it now, and core wouldn't be an issue as I would take the old one in with me when I got it. The other 2 are mail order, so there would be the time to get them, and in the case of the MC I wouldn't get the core charge back for a few weeks.
I did come across a PA Perf repair kit that, amongst other things, replaces the voltage regulator, and works for the OE alt, for $70. The only concern I have here is that one of the comments recommends having a press to install the bearings, which I don't have, nor have access to one.
The only advantage to getting the AZ one is I can have it now, and core wouldn't be an issue as I would take the old one in with me when I got it. The other 2 are mail order, so there would be the time to get them, and in the case of the MC I wouldn't get the core charge back for a few weeks.
I did come across a PA Perf repair kit that, amongst other things, replaces the voltage regulator, and works for the OE alt, for $70. The only concern I have here is that one of the comments recommends having a press to install the bearings, which I don't have, nor have access to one.