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Discussion Starter · #1 ·
I am in a pickle. I have one of my cars with an issue. When the car is running I get a battery light every now and then. But even when the light is on I am getting 13.5V or more at the battery. I used the Ford manual and attempted all the pinpoint tests but I am not certain where some of the circuits they want me to test are since I cannot find a schematic. At any rate, I took the alternator off and had it tested, twice, and it was good. I cleaned all connections and checked the grounds and fuses. With my problem persisting I removed the alternator and replaced it anyway. But I still have the problem.

So to explain the problem. While driving down the road the lights will get brighter and or dimmer. But it isn't just the lights, it is everything, blower motor will go faster and slower etc. So what I am experiencing is a voltage change to the systems. If I monitor the voltage at the battery it will be between 13.95 & 13.5 with the old alternator and 14.25 & 13.5 with the new alternator. This with the lights getting brighter and dimer but not in a rhythmic pattern, it is entirely random and can go for minutes without a change and then start up again.

Any ideas? Anyone have a schematic?
 

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Same issue here on an '04 w/ Duratec... Now getting intermittent "Service Charging System" message and battery light, will turn, hit bump, do nothing, and light will go out. Just tested batt, starter, alt, with ED/18 load tester at work, nothing wrong. Replace batt terminals for minor corrosion and because I hate factory terminals, and problem still there. Going to start checking grounds as I just put it all back together after trans was out for almost 2 years.
 

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Discussion Starter · #6 ·
Sorry for not replying to this with the solution before now. But for me it was a bad computer. I bought a replacement at a junk yard for $75 and then paid $90 for Ford to program it to the car. Then my problem was fixed.
 

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So maybe there is some kind of update to the computer software that can fix this issue? Are there any TSBs out there for this?
 

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Discussion Starter · #9 ·
I had a very hard time with the dealer on my issue. I had diagnosed it to the computer but didn't have the ability to reprogram a computer to the vehicle. I took it to them with the new computer and asked them to put it in for me. The insisted that they could not do that without doing their own diagnostics. I agreed to the one hour of diagnostic labor thinking they would end up putting it in for me. But they didn't, they told me it needed an alternator, which it clearly didn't. The also told me it needed a new harness, which it clearly didn't. I agreed to let them replace the partial harness as it was 'plausible' even thought I had checked it and didn't agree. When this didn't solve the problem they again wanted to replace the alternator and I was furious so I took my car back and began the complaining process.

After about two weeks, they agree to compare this computer to one of my working cars. So I dropped off two of my Tauruses with them and they moved the bad cars computer to the good car. What they found was what I told them, the problem followed the computer. So they put it all back and told me it would be $180 to program the new computer into the bad car. Which I agreed and had them do. Problem solved.

I went round and round with them asking if there were updates or flash upgrades for the computer and they insisted that there were not. Now if we can start a new thread, how can we find a way to program a computer to a car at home, I am all for that thread.

Linc
 

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So is the system voltage regulator integral to the PCM in the later model Tauruses? I'm wondering how the computer caused the charge system to malfunction.
 

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Discussion Starter · #11 ·
No, the voltage regulator is internal to the Alternator. However, the PCM controls the voltage regulator unless it goes into back up mode. So, while the computer monitors battery voltage and Alternator output for a differential. Then uses that differential to determine the correct output of the Alternator. The computers inability to monitor this voltage accurately leads to an erratic charging system.
 

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BTW, found my issue.

Engine ground at pass side firewall, RIGHT up by the underside of the cowl. Loose. Have to send the wifes fingers in there with a ratchet wrench. Hence it was loose, because; I made her loosen it, and then I forgot it was loose.

:facepalm:

Wifey wins again. She goes, hey, you said it might be a ground... what about that one I took off?
 
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