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02 Taurus ses dohc vin s
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Discussion Starter #1 (Edited by Moderator)
02 Taurus with a duratec. I've replaced the battery and just replaced the alternator and doing the exact same thing. Has low voltage add on idle with the AC going and you can watch the headlights dim down. And heads down to about 12.1 volts but if you put it in neutral at stop lights and rev it up it will go up to 14 volts the fan will start blowing good and headlights will brighten up. I think I have noticed the fan speeds fluctuating a little bit and the headlights dimming a little for years but it has gotten worse and now gotten to this point. I would appreciate any help I could get on this issue
 

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See my post in "solutions to common problems" in the post this morning.
Much of a hot weather issue and how much Alt makers put in there. Alt outputs drop ~30% when hot compared to cold. The only time your Alt is "cold" is when you start the engine. The big loads are, cabin fan and rad. fans. Very important to have a strong battery to hold you up when idling.
-chart-
 

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Today, '03 Sable DOHC 130A Alt. Clip from Carchip chart toady ~90F ambient car hot, no headlights as daytime run. Note, when idling I am running off the battery as the Alt can not keep up.
Situation normal.
-chart-
 

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02 Taurus ses dohc vin s
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Discussion Starter #4
Thank you chart maker. But there has to be an answer for it I can't drive around with the headlights dimming at stop lights and the fan speeds dropping and having to put it in park at stop lights and rev It Up, someone on the forum has to have a cure for this issue. I've done voltage drop test on it also and talked with a Ford technician about possible wiring from the PCM to the alternator and or possibly the PCM itself?
 

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Not a problem you are going to fix. See chart, this a Lin Cont stopped for a total traffic stop on 5 lanes. Note, at about 11 minutes, I put it in gear and use the brakes, you see the volts drop. This is without lights on, just A/C and blower. The radiator fan and the climate blower are the big drawers and good deal for the A/C clutch. Then note, when the Alt is hot, you loose ~30% of it's capacity. Then the Alt has minimum cooling at idle. Alt capacity rated at 6K engine rpm and Alt core temp 72F. Good luck with that.
Chart in the Att. by me, and data by Carchip.
-chart-
 

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02 Taurus ses dohc vin s
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Discussion Starter #6
Thank you chart maker , that's really great stuff. I'm not going to give up on this and I will let you know. Will probably take out my transmission driving at this way, putting it in neutral at stop lights and reving it up and such. Thanks again
 

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02 Taurus ses dohc vin s
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Discussion Starter #7
Hi guys. On my 02 Taurus dohc vin S I'm getting low voltage at idle. If I put it in neutral and rev It Up I'm fine ,I get my blower speeds back headlights Brighten xcetera. I put a new battery a Reman Remy alternator did voltage drop test on my positives and grounds, checked the amp draw on my radiator fan motors & blower motor and still doing the exact same thing. I've always noticed this problem over the last 4 years( since I've owned it) headlights dimming, AC blower speed dropping a little but now it's gotten to this point where it is very bad. Do any of my Taurus brothers or sisters have a cure out there for this issue? Thank you guys
 

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Top of the list, need cables in top shape, and grounds, especially the fire wall ground strap. Next very strong battery. With age they have less low charging rate support.
The ground to the fender is key when not running, but when running the ground strap to firewall is key.
-chart-
 

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Mod Edit

The posts for this repair issue have been merged to one thread. Please try to keep it that way, it helps the troubleshoot
 

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02 Taurus ses dohc vin s
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Discussion Starter #10
Yes thank you chart. I wanted to start a new thread on this issue to see if anyone else out there had some ideas
 

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Discussion Starter #11
Top of the list, need cables in top shape, and grounds, especially the fire wall ground strap. Next very strong battery. With age they have less low charging rate support.
The ground to the fender is key when not running, but when running the ground strap to firewall is key.
-chart-
 

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02 Taurus ses dohc vin s
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Discussion Starter #12
Thanks again chart. One thing that was a little iffy was my positive cable from the fuse box to the alternator. Voltage drop was .200 volts. The rest of my voltage drops were showing way under .100
 

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Discussion Starter #13
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hey chart maker I had a tenth of a volt voltage drop on ground strap to the fender well and the ground strap to the firewall and the positive cable to the alternator. I made new cables and helped the grounds but not the positive. Load tested the brand new Everstart battery and it tested good at 650 CCA. The one picture with the d v o m hooked up is Max AC hi blower with the headlights on in Park and hot. Seems like it's doing a little bit better , I will have to take it on some more test drives and see. Any other ideas you might have on this would be deeply appreciated thank you
 

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Latest info. It's doing good since I replaced all the battery cables. AC blower speeds drop a little bit and headlights dim a little bit at traffic lights in 110 degree Vegas weather, very livable now. (Also looking back damage may have occurred to the firewall ground while tilting the motor to do the right exhaust manifold, I made a YouTube video on that also)Thanks for all the help chart maker and Taurus Club
 
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