Alternator Or Battery Or Both?

Dondre Richards · Oct 8, 2014

I have a 2002 Base Mustang and the Alternator was giving me a bit of a problem. I took the new alternator out of a focus and put that one in the housing for the mustang. the Alternator works but only after i rev the engine up to 3000 rpm other than that the battery only gives me 11 voltage and slowly dies down but after revving the engine to goes up to 13v and works perfectly.

Noobz347 · Oct 9, 2014

What is your question? Should you install an alternator manufactured for your specific car? Yes.

Dondre Richards · Oct 9, 2014

Noobz347 said:
What is your question? Should you install an alternator manufactured for your specific car? Yes.

No. My question is what could be the problem because i have to rev the engine high enough for the alternator to start working

Noobz347 · Oct 9, 2014

Generally, it means that the it's not spinning fast enough to activate the regulator. If the alternator that you installed is internally regulated (most modern are) then the exciter is set for the RPM of the car that it was designed for.

There's a few things that come into play including idle RPM and pulley size for both, the alternator and the crank.

Pretty kewl that you had the idea to gut an alt and put it into another case that fit but I think you'd be better off with a junk yard alt from car similar to yours.

You might check the field wire going to the alt but it sounds as if it's working perfectly fine to me. It's just not coming on at the desired point. It's coming on a the desired point for the Focus you pulled it out of.

Dondre Richards · Oct 9, 2014

Noobz347 said:
Generally, it means that the it's not spinning fast enough to activate the regulator. If the alternator that you installed is internally regulated (most modern are) then the exciter is set for the RPM of the car that it was designed for.

There's a few things that come into play including idle RPM and pulley size for both, the alternator and the crank.

Pretty kewl that you had the idea to gut an alt and put it into another case that fit but I think you'd be better off with a junk yard alt from car similar to yours.

You might check the field wire going to the alt but it sounds as if it's working perfectly fine to me. It's just not coming on at the desired point. It's coming on a the desired point for the Focus you pulled it out of.

The pulley from the one i put in was smaller than the one for the 'Stang. Do you think that it may work if i changed them?

Noobz347 · Oct 9, 2014

Dondre Richards said:
The pulley from the one i put in was smaller than the one for the 'Stang. Do you think that it may work if i changed them?

It's free to try. If it were me and I'm trying to keep the costs down, I would try it.

Alternator pulleys can be a BITCH though. If you've never replaced one, pull up a youtube video on it before mauling the parts.

Dondre Richards · Oct 9, 2014

Noobz347 said:
It's free to try. If it were me and I'm trying to keep the costs down, I would try it.

Alternator pulleys can be a **** though. If you've never replaced one, pull up a youtube video on it before mauling the parts.

we had to take off the pulley to gut the alt wasnt much of a big deal lol but i'll try that and see how it does

7991LXnSHO · Oct 26, 2014

You can also have pep auto champion napa bench test it for free with the Mudtang pulley, then swap them for one that has a warranty if it it FUBAR.

Swapping pulleys is easy with an impact tool and the right socket.

Alternator Or Battery Or Both?

Dondre Richards

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Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

Dondre Richards

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Noobz347

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Dondre Richards

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Noobz347

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Dondre Richards

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7991LXnSHO

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