Alternator normal voltage?

[JonJon]

I just replaced my battery in my 99 GT with an Optima Red Top on Monday. Tuesday I drove to work and home, no problems. On Wednesday, I started it briefly to move it off the street because of the snow. On Thursday morning, the car wouldn't start. I got a jump tonight and my friend did some battery/alternator testing.

Battery puts out 12.4v when off.
While running, alternator puts out 13.94v with no accessories on at 1500RPM.
While running, alternator puts out 13.7v with headlights, fog lights, and heater on full at 2000RPM.

I did a search here and some people said 14.4v is good, some have said "around 14v" is good... Is there any definitive yes or no whether my alternator could be on the outs? Is there any other test I could do? After I got the jump I drove around for an hour. Once I parked it, we let it sit for about 30 minutes and then we did the tests.

EDIT: I have Steeda Underdrive Pulleys if that makes an impact as well...

 

[hotmustang331]

My car sees 14V @ night.

13.5 or so in the day.

long time no see mang....we know how it works, come around when you need something... LOL J/K

 

[JonJon]

LOL
It's a double edged sword, it's good that I keep away, means the Stang works and it also means that I'm probably being productive instead of post whoring in talk

Does the time of day have an impact? Or by 'night' do you mean when you're using your headlights? So it sounds like my numbers are higher than yours and maybe ok then... I basically just don't want to be driving around to work and etc and having the car not start. So if the alternator isn't charging enough, I want to replace it sooner than after being stranded :\

 

[hotmustang331]

No at night im meaning headlights on LOL.

What worries me is that your seeing LESS charge with everything on then with everything off. Mine always shows more when the lights are on.

Infact im going to go check right now with lights out and lights on @ 1500RPM and 2K

 

[hotmustang331]

LOL well unless my alt just kicked the bucket mines doing what your is. I KNOW iv seen it do just the opposite all this time...WEIRD stuff. But my car is missing right now....actually over the past 2 weeks LOL.

SO mine pulls 13.7V after letting it warm up and recharge the battery with brights on and heater on full blast.

Everything off it goes to around 13.9.

For the first 5-10 minutes it was showing 14-14.2Vs reguardless if the lights were on or off. And in the tests, RPM made no noticable difference.

Hope that helps, and for now all I can say is that its probbably fine, since mine is doing the same thing and has zero signs of a dead battery.

 

[JonJon]

Thanks for doing those checks :grouphug:

but when I tried to start the car this morning, no go. Last night I drove it for over an hour to let it charge and started it for 5 minutes (to do the volt testing).

Does that sound like the battery must be draining somehow overnight?

 

[hotmustang331]

Yes, check to see if there is any voltage drain. Im pretty sure you can buy a little meter that when hooked to the battery cable will show any drain.

I remember one guy on here found some sort of a short in his dome light or something that was draining his battery...he was having the same issues as you, except his would take a few days to kill the battery. Do you have a car alarm or any aftermarket devices hooked up to your power?

 

[blkhorse]

charging voltage is normally in the 13.8 to 14.2V range.unhook yor battery overnight see if that helps.you can also check for draw with your multimeter. set on dc amps ,shut off all acc.(including shutting doors)unhook battery and put multimeter inline betwen cable and battery.it may intially start high but should settle to < 80 milliamps(radio clock,keepalive etc)

 

[2000fordstanggt]

dont forget to check the mach 460 amprack for a draw on the battery.

 

[JonJon]

Thanks for the tips guys. I was waiting for a friend to come over with test light and multimeter on sunday but he ended up being busy. I also disconnected my aftermarket amp from the battery on Saturday night, Sunday the battery was dead again. Went to Sears today, Sears guy tested and says its definitely the alt. I haven't had time (busy time at work) to try anything else.

So, anything special I should look out for on alts? Or just goto Advance Auto and pick up any ole thing? Looks liek ~$220 (after giving them the old one). Oddly, the Cobra one is $160. Would 10 more amps hurt?
Ford wants $350.

 

[Smokeurhonda]

does not sound like an alternator bro....sounds like a parasitic draw....double check your key off power draw before you go and buy a new alternator.

 

[urban96]

a bad alt can still put out voltage when running but cause a draw when not running. if something in there is shorted out it would cause a draw. if you get the test light and do the draw tests pull the fuse for the alt and check that way

 

[JonJon]

Sears did all those tests, batt, alt, draw, cables, etc (It's a "battery and electrical system test" for $13)
I got a ride to work today because it's billing period, too busy to deal with car. After work I'll see if it starts up and order a new alt if it does.
<3 urban for your help yesterday

 

[JonJon]

Ok. This is an OLD thread but I wanted to just let you guys know the terrible mess that I went through.

So after Sears did a charging system test they determined it was the alt. I got a new alt and dropped it in. Car still wouldn't start reliably. I had to wait 2 weeks after that to try to do a draw test due to busy time at work and the holidays. My friend and I tried to do a draw test with test light as best we could in the freezing cold... and then we found out that without letting GEM sleep, the results are kind of erroneous. So that was a waste of an hour or so in the cold.

I got fed up and got to the point where I really couldn't depend (or want to bother) others to give me a ride around... so I called Ford and reluctantly dropped it off there. They did a charging system test, everything passed good. I asked them what was the next step, they said an amp draw test. They let the car sit over the weekend and did an amp draw on Monday. No failures. I asked them to let it sit a few more days and try again. On Friday, they still believed the car was perfectly fine and thought I was a sucker for paying them $120 for those 2 tests (at least they would do repeat tests for free until they found a problem). Well I picked the car up Friday kind of frustrated because if they found no problem, what the hell was I going to do now? Well I took the car back to work around 3PM, then I went snowboarding. When we got back around 9:30PM... the car wouldn't start. LUCKY ME!

So I call up Ford again and ask them what I can do. He suggested dropping it off again and they would just periodically test it until they could figure out the problem. I was busy at work again so I didn't have a chance to do that until this past Tuesday night. I did think the car struggled to start that night, the voltage meter dropped from ~70% to 35% while cranking. I expected the car wouldn't start in the morning. On Wednesday morning, service advisor calls back and tells me the battery is bad, he thinks a cell was malfunctioning. 57 CCA. I went by and picked up the Optima Red Top and returned it and just picked up a cheapo one. Car has been running perfect for the past 2 days.

Obviously I won't believe that was the problem until I run the car for a month or so without incident. Previously I had a stretch where I was able to drive with the suspected defective battery for a week or two and then it would drain too low again to start. So I HOPE it was just that...

So, a summary of costs:
$156 Optima Red Top (returned)
$13 Sears charging system test
$200 alternator
$120 Ford charging and amp draw tests
$80 not an Optima Red Top battery
2 months of not having a reliable car (Stang is my only car)

Everyone kept telling me to just get a new car, F that. Love this car.