Alternator Reading 13.4
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Alternator Reading 13.4
I got stranded last week and bought a new battery. It has started every morning for a week, but just to be sure I took it to AutoZone to get the alternator tested. The guy hooked up his computer and it read 13.4 and told me that it needed be replaced ASAP. I was reading a couple places online and they all said if it reads under 13 that its going bad/is bad. Mainly I just want to know if I can get around safely for a week of two. Any input would be appreciated. Thanks guys.
Post Fiend
Joined: Jul 2005
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Specifics please.
Gas or diesel?
One or two battery? Did you just replace one of two?
OEM Ford alternator?
Do you run additional (non stock) electrical loads like seat warmers, ghetto blasters, plows, emergency lights, winches, etc?
Cables? Stock?
Gas or diesel?
One or two battery? Did you just replace one of two?
OEM Ford alternator?
Do you run additional (non stock) electrical loads like seat warmers, ghetto blasters, plows, emergency lights, winches, etc?
Cables? Stock?
Post Fiend
Joined: Jul 2005
Posts: 6,127
Likes: 6
Double check Ford specs for the alternator voltage.
But to me, that is pretty normal voltage.
If you have AC on, etc. it would pull it down even more.
The definitive test --- hook up a voltmeter to, eg the cigarette lighter.
Fully charge battery overnight.
Verify battery cables / alternator cables have no problem etc.
Take it for a long drive (over 5 or 10 miles, so it has time to charge battery up the power used in starting).
Then, measure the voltage with engine rpm constant (above 2,000) with no headlights, etc. on.
If you are over 13.5 volt range, you are probably OK for quite a while.
If you are over high 13s or around 14.
There is nothing wrong.
A Voltage test by itself tell you not much --- you need simultaneous measure of voltage and current (to get power output).
As you can see, I think the fella that sold you the line is trying to sell you something you probably don't need.
Oh.. now for my advert.
Replace it only with a Ford reman / new with exactly the same part number.
You will find the part will outlast the average Autozone alternator by far.
Even if it comes with a lifetime warranty, you still have the hassle of putting it in --- and having a failure on the side of the road.
But to me, that is pretty normal voltage.
If you have AC on, etc. it would pull it down even more.
The definitive test --- hook up a voltmeter to, eg the cigarette lighter.
Fully charge battery overnight.
Verify battery cables / alternator cables have no problem etc.
Take it for a long drive (over 5 or 10 miles, so it has time to charge battery up the power used in starting).
Then, measure the voltage with engine rpm constant (above 2,000) with no headlights, etc. on.
If you are over 13.5 volt range, you are probably OK for quite a while.
If you are over high 13s or around 14.
There is nothing wrong.
A Voltage test by itself tell you not much --- you need simultaneous measure of voltage and current (to get power output).
As you can see, I think the fella that sold you the line is trying to sell you something you probably don't need.
Oh.. now for my advert.
Replace it only with a Ford reman / new with exactly the same part number.
You will find the part will outlast the average Autozone alternator by far.
Even if it comes with a lifetime warranty, you still have the hassle of putting it in --- and having a failure on the side of the road.
Post Fiend
Joined: Jul 2005
Posts: 6,127
Likes: 6
Charge the battery full tonite.
The reserve capacity (you should know or can look it up) for your new battery is published.
Bet you that can power you for 30 min or so with the alternator completely dead, if you turned everything non-essential off (headlights, radio, etc.)
I would hook up a volt meter and monitor voltage carefully for a week, but I would not hesitate to think there is nothing wrong and delay replacing the alternator indefinitely unless I see other symptoms of failure.
The reserve capacity (you should know or can look it up) for your new battery is published.
Bet you that can power you for 30 min or so with the alternator completely dead, if you turned everything non-essential off (headlights, radio, etc.)
I would hook up a volt meter and monitor voltage carefully for a week, but I would not hesitate to think there is nothing wrong and delay replacing the alternator indefinitely unless I see other symptoms of failure.
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Freshman User
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I just checked and the reserve capacity is 150 mins. I am going to charge it overnight. I drove it a half hour home when I replaced it, started it several times in the drive way, and drove it around 5 miles to autozone and back. The lights aren't dimming or anything, I think it's fine.
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Logistics Pro
Joined: Jan 2010
Posts: 4,110
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Did you actually pull the alternator and have them bench-test it, or did you simply have them do the 'whole system' test in the parking lot? The 'whole system' test doesn't take into account the draw of charging after starting, any lights that might be on (such as your interior lights from the door being open, etc) or the fact that your fuel pump might also be running. A bench test actually tells you what the alternator is putting out (both volts and amps), and tests what it does under a full draw. I always recommend a bench test before deciding if you need to replace an alternator.
BTW, most Autozone employees are going to try to get you to replace something whether it needs to be or not. I also had one try to tell me O2 sensors don't tell you how your catalytic converter is operating. THAT was a classic conversation.
BTW, most Autozone employees are going to try to get you to replace something whether it needs to be or not. I also had one try to tell me O2 sensors don't tell you how your catalytic converter is operating. THAT was a classic conversation.
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