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Topic Review (Newest First)
08-10-2011 09:41 AM
sham63 Kind of late for the original poster, but I just had the same issue of the battery light being on for no reason. My battery is only a year old, and the alternator is outputting 14.4v. The cause for my car was fuse 10 in the fuse box under the hood. It is for the battery sensor, diagnostic plug. The fuse was blown, put in a new one and the light went out. I wonder if it blew because my drivers side lock actuator went out and blew the fuse for that. It caused the dome light to dim a lot, and the others doors unlocked real slow. I need to get an actuator and replace it.
09-12-2010 06:58 AM
Usagi Last time i saw numbers like that, my alternator was breathing its last. Then again, the low voltage at idle was accompanied by the requisite "moan" alt's tend to make when they die...
09-12-2010 02:19 AM
sailor Posted via FF MobileShucks..... well keep an eye on it, should charge enough to be OK as it`s at least maintaining battery voltage at idle with a load - not dropping below to indicate a draw on the battery at idle. And it charges fine once off idle to recharge the batt. from starting loads... Not tragic, just won`t recharge appreciably at idle...
09-11-2010 03:30 AM
Adventure-Biker So I installed a new battery today. Luckily my old one was still under the 2 year warranty so the new one was an even exchange and didn't cost me a cent out of pocket.

Brought it home, put it on the trickle charger (who knows how long it sat on the shelf at the store), let it fully charge, and then installed it on the car. With the car turned off battery voltage read 12.85v. Start car (engine warm, no lights or accessories on) and charging voltage is still under 13v at idle. Turned on lights and everything electrical I could turn on and charging voltage falls below 12.6v at idle.

Voltage quickly climbs to 13.5-13.6v with everything electrical ON at about 900-1000rpm. Same RPM with everything turned off yields about 14.6v

I guess this H.O. alternator I bought really does have to spin at a higher RPM before it does anything :(
09-10-2010 03:28 PM
sailor Posted via FF MobileOkay, after a drive to warm up I`m getting 14.5 volts at about 700 rpm, so the higher idle was due to not fully warm & output is OK at low rpm - no help, but a better reference than my false idle #`s.
09-10-2010 02:00 PM
sailor Posted via FF MobileProb should have run mine longer for a fully warm reference, but it ran recently so not really "cold". 6-700 isn`t unusual as a low idle speed, just didn`t know your "normal" in the past! In my case I can`t remember right now as I didn`t pay close attention (working OK, so you don`t check too close) Duratec normal & Zetec normal may be different anyways..... `fraid I`ll have to recheck my "normal" in a bit for a better reference, 700 does sound right for an automatic when in gear, 6-700 is my memory for "normal" in that case when fully warmed up.... Good output at idle is the whole point to alternators, as opposed to old time generators, interesting that you get a dramatic increase in output between 700 & 900. I`ll get back when I recheck idle after fully warm when driven.... maybe get out the voltmeter for another reference set of #`s.
09-10-2010 01:12 PM
One more thing...

I'm wondering if there are any unseen issues with the battery itself? I installed this battery new less than 12 months ago and to this day I have never had any issues with the battery itself, but due to the recent alternator failure I had this caused the battery to go completely dead on about 3-5 occasions.

I know this can be detrimental to any lead acid battery. The hot climate I live in probably makes matters worse. The battery still starts the car fine and accepts a slow charge from my WalMart charger. After charging it reads a good 12.68-12.8v although this could possibly just be a 'surface charge' reading???

Any ideas whether I should replace the battery? It was just a low cost replacement to begin with but I'd rather not buy another battery right now if I can help it.

One thing I remember is that my alternator failed a few years ago at around 40k miles while the car was still under factory warranty. Rather than fiddle with it myself I took the car to the dealer (considering that the warranty was still in effect). Before taking it to them I verified little or no charging output myself. They replaced the alternator- and ALSO the battery. Prior to that I never had any issues directly related to the battery but they replaced it anyway- I was only expecting them to replace the alt. This has me wondering if my present battery has some unseen fault and should be replaced.
09-10-2010 12:57 PM
Originally Posted by sailor View Post
Posted via FF MobileSeems like the current problem is a lower than normal Idle RPM. Mine Idles at about 900 when warm, and readjusts to that when A/C is engaged (pops higher then settles down) so that seems like the normal speed for idle. If the IAC seems to be responding normally you may have a vacuum leak or other cause for low idle.... Others may know your normal idle, I can`t see your model info on Mobile, just guessing that all models have similar std. Idle RPM....
I have a wagon with the Zetec engine. I got this car brand new and the idle speed as always been around 700rpm from day one (after warm-up). Of course the idle from a cold start is a little higher (somewhere around 1000-1100). I'm assuming the idle air control is working correctly- with the air conditioner on the idle speed doesn't increase but pretty much stays constant around 700rpm (even if the electric fans are on out front).

Like I said, the car has always worked like this. I never had any low charging output issues at idle with the OEM alternator.

The missus has the same car as I do (SE wagon), only one year older, less factory options, and with quite higher mileage. Same Zetec engine however. Her's idles at around 700rpm after warm up also. I checked charging voltage on her car at idle yesterday (no lights or other electrical stuff on) and it produces a good 14.0-14.2v, at idle. Then I turned on everything I could possibly turn on- lights, heater blower, front and rear windshield wipers, rear defogger, interior vanity lights, radio, and the car still produced well over 13.2v at idle- still more than enough to charge the battery.

So I am left to conclude that the Bosch H.O. I put in my car won't really work unless I am driving at least 1000rpm, which is definitely on again, off again in city driving (NOT good for the battery). And with the amount of electrical load I put on my car, this is a problem :(
09-10-2010 12:15 PM
sailor Posted via FF MobileSeems like the current problem is a lower than normal Idle RPM. Mine Idles at about 900 when warm, and readjusts to that when A/C is engaged (pops higher then settles down) so that seems like the normal speed for idle. If the IAC seems to be responding normally you may have a vacuum leak or other cause for low idle.... Others may know your normal idle, I can`t see your model info on Mobile, just guessing that all models have similar std. Idle RPM....
09-09-2010 02:29 PM
Adventure-Biker The battery light in my car came on while driving. After I turned the car off I noticed that the battery light came on each time about 15 seconds after starting the engine. I checked the charging voltage and amperage with a digital mulitimeter- charging system was working but rather weak. The next day I fully charged the battery and took the car out for a drive...the battery light was on the entire time and the car completely died with a dead battery about 30-40 minutes after driving. All this while my multimeter was showing alternator output (however low and weak).

I decided to upgrade and ordered a new Bosch hi-output replacement (220 amp) for $249.00 shipped from an eBay seller since I live in a hot climate, run the air conditioner, and also tend to run a power inverter and other electrical accessories inside the car. I installed the alternator myself- took me about 3hrs.

Battery light no longer comes on. Charging voltage is a solid 14.2-14.4 volts off-idle. I didn't check the charging amperage because it would probably fry my multimeter.

But now I have a new "problem". This new Bosch hi-output alternator seems to have to spin at a higher RPM before it kicks in and actually charges. My car idles at about 700RPM and I am getting less than 12.5v at the battery. If I increase engine RPM to 900 then charging voltage immediately jumps to a solid 14.2-14.4v. The Bosch alt has the same diameter pulley as the OEM alt I removed, so alternator shaft speed is exactly the same.

I mostly drive my car in the lower RPM ranges and also do a lot of relatively shorter distances in city (ie. stop and go driving), so this poses a problem - my battery now is usually discharging considering the way I drive, unless I hit the open road or something (which I don't do too often).

I never had this low rpm charging issue with the stock alternator :(
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