Mechanics

ALTERNATOR DROPS OUT

2002 Ford Taurus

Electrical problem
2002 Ford Taurus 6 cyl Front Wheel Drive Automatic 130000 miles

2002 Ford Taurus SE 3.0L V6 130000 miles, the alternator drops out intermittently. The alternator is a rebuilt one from a reputable shop, they have inspected it and found no problems. Battery is the second brand new battery, the first died from being discharged too deeply. The problem seems completely intermittent and I can't reproduce it, it just happens randomly. When working it charges beautifully, it regulates at 14.2V and drops to 14.1 with headlights & ac on.

The diagram from Chiltons & Haynes manual both list the alternator as having a Yel/Wht charging wire, an Org/Lt Blu wire which goes to battery, Lt Grn/Red which goes to instrument cluster, and Wht/Blk wire which goes back to alternator on cars w/ 3.0L 12Valve & FFV only.

This alternator actually has Yel/Wht which is charging line to battery, Or/Yel which goes to battery, Lt Grn/Red which I can't figure out, and Gry/Wht or Yel which I can't figure out.

Anyone know what the wires actually go to? It doesn't seem to quite match up with the diagram, neither the color codes or the signals. The Grn/Red line seems to change with varying load, like the comptuer feeds the alternator some regulating voltage, I.E. When headlights are switched on, there is a few volts on the line until it brings the battery up to 14.2V, then it drops off. I assume the Gry/Wht or Yel line goes to the instrument cluster, as when the alternator was in fault, the line was.6VDC which would turn the light on, and when it is working it is 4-6VDC.

I'm out of ideas, I'm just trying to help a guy who's down on his luck and just lost his job. He can't afford a new alternator, and I'm not sure if it's even bad. He doesn't know why it was replaced in the first place, but my suspicion is the original may not have been bad. At this point, I think he may just have to replace the alternator again, but if I can find out what the lines actually do or at least where they go I may stand a chance.
Avatar
Skamego
February 13, 2010.



There is a Tech bulliten out on 02 and 03's here it is, check for these codes with a scan tool. if found, have the PCM flashed...
MALFUNCTION INDICATOR LAMP (MIL) ILLUMINATED WITH DIAGNOSTIC TROUBLE CODES (DTCS) P0300, P0316 OR P030X - NO CRANK BATTERY DISCHARGED TECHNICAL SERVICE BULLETIN Reference Number(s): 04-25-14,  Date of Issue:   December 27, 2004 FORD: 2002-2003 Taurus MERCURY: 2002-2003 Sable Related Ref Number(s): 04-25-14 ARTICLE BEGINNING DESCRIPTION MALFUNCTION INDICATOR LAMP (MIL) ILLUMINATED WITH DIAGNOSTIC TROUBLE CODES (DTCS) P0300, P0316 OR P030X - NO CRANK BATTERY DISCHARGED ISSUE Some 2002-2003 Taurus/Sable vehicles may exhibit one or both of the following conditions: No crank, battery discharged • Malfunction indicator lamp (MIL) illuminated with P0300, P0316 or P030x misfire diagnostic trouble codes (DTCs) (3.0L 2V only) • ACTION Reprogram the powertrain control module (PCM) to the latest calibration using WDS release B34.7 or higher. Calibration files may also be obtained at http://www.motorcraft.com. If misfire DTCs or a charging concern is still present after PCM reprogramming, perform normal diagnostics. Replace components only if tests indicate replacement is necessary. WARRANTY INFORMATION WARRANTY STATUS: Eligible Under Provisions Of New Vehicle Limited Warranty Coverage And Emissions Warranty Coverage. WARRANTY INFORMATION
Page 1 of 2 MALFUNCTION INDICATOR LAMP (MIL) ILLUMINATED WITH DIAGNOSTIC T...

Merlin2021
Feb 14, 2010.
Thanks for the info, I told him to take to Ford and see if they'll flash the PCM. On the very likely chance they won't cover the cost, I doubt he'll go for it, they can't even buy propane for heat this winter. From the research I did it looks like the 6G alternator uses multiple different types of voltage regulators, and the one he has is likely one of the ones that is controlled by the PCM. I'm wondering if I buy an older regulator that just uses the battery wire for the voltage control and put that it what problems it may cause. I figure the computer may think the alternator isn't working due to the differences in pins, probably pop up a trouble code, but at least it would charge. Thoughts?
Steve

Tiny
Skamego
Feb 14, 2010.
Or maybe fry the pcm?

Merlin2021
Feb 15, 2010.
Good point.

It's possible the alternator shop put the wrong regulator back in the rebuilt alternator, this one's never worked right. That's why I'm trying to find out which color wire is which, so I can see which regulator this car's supposed to have in it.

I have the VIN so I may go to Ford and see if they can tell me which alternator it's supposed to have and maybe I can tell from that.

Thanks for the help, I'll post as soon as I find out if they got the PCM Flashed.

Tiny
Skamego
Feb 15, 2010.
First, like the tech bulliten said, are there misfire codes? check engine light on, with p0300 or P03xxx up to P0306? Or P0316? If not, and he never had this problem before, suspect a bad or incorrect alternator!


http://www.2carpros.com/forum/automotive_pictures/62217_Charging_Circuit_1.jpg



http://www.2carpros.com/forum/automotive_pictures/62217_Gen_Specs_1.jpg


Merlin2021
Feb 15, 2010.
Unfortunately, I have lent my code reader out so I couldn't let him borrow it. The check engine light was on so we went to the local auto parts place but the light had gone off by the time we got there & they couldn't pull any codes. He said the light came back on last night so I told him to get it to the dealership asap, hopefully there will be a code. I don't know if he's had this problem before, I really don't have a good history of this car. The alternator and battery were replaced for some reason, he didn't know why though. I wouldn't be surprised if the alternator shop just put a new regulator in it that physically fit and it may not be electrically proper for this car. It looks like they've used a few different pinouts over the years so it's definitely possible. What's strange is it works fine most of the time and regulates beautifully, it just randomly stops charging until it dies. Jump it and it'll start charging again. If it was the wrong regulator I wouldn't think it would work at all.

I appreciate the help on this. I'm sure you've gathered I'm not a mechanic, just trying to help a friend out, so your input has been really valuable. I had no idea there was a TSB for this problem, honestly I didn't even think to look for one.

I'll post the response he gets from Ford once I hear back.

Tiny
Skamego
Feb 15, 2010.
I know a few mechanics that wouldnt have tested as much as you have!

Merlin2021
Feb 15, 2010.
He got the codes read. He said they said there was a bad crankshaft sensor & misfire on cyl 3, but the only code # on the paper was P0316. I told him to get his butt to Ford and see what they think, and if they flash the computer we'll see if it still has troubles afterwords.

Tiny
Skamego
Feb 18, 2010.
I agree!

Merlin2021
Feb 19, 2010.