Alternator question?

10thAnnvCobra

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I was driving yesterday in the rain from tropical strom Hannah and the battery light came on and then the ABS light. The wipers slowed and the car wasn't running right, I had to drive "gently". When I got home it wouldn't turn over, no juice. :shrug: I have just hit 70,000 miles and the battery and alternator are original. I assume that the alternator has failed. I will use a meter to test the volts at the battery while it is running with accessories on. I may need an alternator and a battery.

My question... can I test the battery with a voltmeter? I know I can use it to test the alternator. I plan to test it at the battery while running with accessories turned on to create a load. I did a search and it seems that anything under 12.7 volts is bad. If I replace the alternator, which is the best choice? I am leaning towards a new Motorcraft (not remanufactured). Are there better choices? If I have to replace the battery what do you folks suggest? Optima yellow top, red top or just a standard replacement Deka battery from NAPA?

Since my car is a daily driver this is an urgent problem. I need to fix it ASAP. Any comments or suggestions are greatly appreciated.

Thanks
:beer:
 

10thAnnvCobra

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No replies? Well, I've figured out that I can only test the alternator with my voltmeter. I'll have to get the battery tested. I'm planning on using a new Motorcraft alternator unless someone can suggest something better. Are the Optima batteries worth the extra money?
 

Juruense

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AutoZone will test the whole charging system for free right in the parking lot. Def sounds like batt or alt could also be corroded connection somewhere.
 

04sleeper

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You should be able to test the alternator output with the volt meter. A better way would be to drive it and datalog it with an XCal or something similar and see what it's actually doing while driving, or take it our and have it bench tested at a local auto parts store.

For the battery, I have never had any luck with the Optimas. I see that your car is an 03 and you say that you still have the original battery. Most batteries last around 4-5 years and then it is time for a new one. So yours is doing well.

I would get another factory battery that you know will last you another 5+ years and check the alternator.

If you want to replace the alternator then I would get one from here. http://www.modularfords.com/forums/showthread.php?t=115494
 

Juruense

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You do not have to take the alt out for autozone to test it they do it in the parking lot in the car.
 

04sleeper

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You do not have to take the alt out for autozone to test it they do it in the parking lot in the car.
I have never seen them do that. I have always brought it in.

I hate to say it but I wouldn't trust anyone at any Autozone around here to test anything on the car.
 

Juruense

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Well I have had them do it with my Civic, they roll a cart out to the car hook it up and with the engine running they test out the whole charging system. It looks like a monkey could do it so they probably are up to the task... :lol1:
 

10thAnnvCobra

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I hate to say it but I wouldn't trust anyone at any Autozone around here to test anything on the car.

I would tend to agree, but testing the battery should be a simple task. The alternator I will test myself with a voltmeter. I have an Xcal II but I am concerned about driving it with the low battery and "bad" alternator. I think the voltmeter will work.

Thanks for the replies.
 

blksvtCOBRA714

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i had the same problem with my cobra about 3 months ago. ended up being the alternator went bad. I just bought a remanufactured oem alternator through ford and it works fine. It is covered for a year including labor, so if it goes up again, I can get it replaced for free. My battery was fine after the alternator blew, I wouldn't think you would need to replace your battery
 

10thAnnvCobra

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It was one of the links on the Modular Ford link you posted. I think I'm just going to go with a new Ford Motorcraft alternator which I should be able to pick up from a local dealer. Then I will have it quickly and won't be waiting for delivery. I'll check the output of mine and get the new one if I have to.

Thanks for the replies.
:beer:
 

10thAnnvCobra

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Ok, I used my voltmeter this morning. At the battery terminals while idling with no accessories turned on / 12.4 to 12.5 volts. At the battery terminals while idling with all accessories turned on / 11.9 to 12.0 volts.

That seems way low to me and I think the alternator is not putting out. What do you think?

Thanks. :beer:
 

Nutty 5.0

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Yes, get an alternator and a battery. I have a good stock one if you want to use it (I'm in B-boro). I got one from the fords that modular link above from Start and Charge and highly recommend that.
 

04sleeper

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Ok, I used my voltmeter this morning. At the battery terminals while idling with no accessories turned on / 12.4 to 12.5 volts. At the battery terminals while idling with all accessories turned on / 11.9 to 12.0 volts.

That seems way low to me and I think the alternator is not putting out. What do you think?

Thanks. :beer:
Yes, That is too low.

I would replace the alternator and battery. (Since your is more than 4 years old)

One thing to mention is the importance of keeping proper voltage on supercharged Cobras. Voltage feeds the fuel pumps and ignition on these cars. With too low of voltage, you are at risk of running out of fuel or ignition. Both could cause you to loose an engine.

With a N/A car it is not as aparent becuase there is a lot less cylinder pressure and most of the time does little to no damage to the engine.

Just a little info I thought might be worth mentioning.
 

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