Alternator, Battery, or other?

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bmw036

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Ok, my battery seems to drain over time. I tested the alternator with a multimeter and it's at ~13.9V. The car runs great with a jumpstart, but it seems to drain after a few days if resonably charged. I don't think any lights or accessories are staying on...

Also I just let the car run for ~25mins and I checked it again and it was ~13.4V vs 13.9V earlier (seems a little low, dunno if that means anything)... it did get enough charge to restart the engine after turning it off (barely though).

I have had alternator problems before, I went throught about 3 OReilly's refurb alts till I finally got a good one (should have read posts from this forum 1st :mad:). I also had a Oreilly's battery go out on me after ~1.5yrs, and the same brand replacement is currently in the car...

Not sure what I should do. I was thinking starting by replacing the battery, but what do yall think? battery or alternator or something else?
 
If the car is losing voltage while running, you either have an alternator problem, or your battery connections or grounds are bad.

Either way, I would suggest one of the Ford factory Cobra alternators for sale on this forum, and cleaning up your contacts, especially since your luck with those reman alternators has been less than spectacular.
 
take out the alt and get it tested at pepboys for free. its "2" bolts to get the alt off, and push the tensioner for the belt. I had a hell of a time getting my alt to set on the tester at my pepboys but i got it done, if they tell you they cant test it, tell them bs, you can, dont slack off.
 
13.9 - 13.4 at what rpm?

bmw036 said:
Ok, my battery seems to drain over time. I tested the alternator with a multimeter and it's at ~13.9V. The car runs great with a jumpstart, but it seems to drain after a few days if resonably charged. I don't think any lights or accessories are staying on...

Also I just let the car run for ~25mins and I checked it again and it was ~13.4V vs 13.9V earlier (seems a little low, dunno if that means anything)... it did get enough charge to restart the engine after turning it off (barely though).

I have had alternator problems before, I went throught about 3 OReilly's refurb alts till I finally got a good one (should have read posts from this forum 1st :mad:). I also had a Oreilly's battery go out on me after ~1.5yrs, and the same brand replacement is currently in the car...

Not sure what I should do. I was thinking starting by replacing the battery, but what do yall think? battery or alternator or something else?
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It is not unusual for the output from the alternator to go down a little after the car has run for a bit. At what rpm were you testing. In order to get a true readingfrom the alternator, it has to be above 1500 RPM's. Sounds like a bad battery to me. And you do not have to take your alternator out of the car to have it tested. As long as the car is able to run, they can test it. It is a pretty good indication that the battery is bad if the car will stay running after you jump start it. That means that the alternator is outputting enough current to keep things going. If the alternator is bad, and the battery is good, you will have a massive loss of power and the car will eventually shutoff as the battery gets low.
 
bufordtpisser - good point, the car was just idleing.

I'm trying a new battery, got a motorcraft BXT65-650 coming in tomorrow and I'm gonna clean the connections. Hopefully the new battery fixes my problems...
 
bmw036 said:
I'm ignorant here, how would I go about doing this?
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The parts stores sell them as "circuit testers," basically run a light bulb between the battery terminal and the battery cable. If it lights up you have a drain (clock, radio presets, etc shouldn't draw enough power to light the bulb,) then you can start pulling fuses and replacing them one by one until it goes out, that will at least let you know what circuit has the drain on it.
 
update - new battery fixed all my problems up. Freaking autozone brand batterys go out almost as much as their alternators... got a motorcraft so hopefully this doesnt happen again
 
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