Careless00045

Hello everyone,
2006 Mustang Base 4.0L
Today my car just shut off while driving, first all the lights went off then after while the car shut off!
I asked someone to Jump my car! and that started the engine for few mints only then shut down again ( after removing the jump cable )!
So right a way i went and i bought a new battery
and installed it and all is good.

So i drove it home and was completely fine,
So i did this test, with the car running i removed the Negative cable and the car shut off!!!
That means the alternator is not charging ? or is it something else?
coz i think the new battery will lose charge as well as the old battery!
Help !
Thank to all.

GrayPony

You can check older cars that way because they have a mechanical voltage regulator. Doing that that on a newer car with an electronic voltage regulator
can cause it to fail. The correct way is to have someone with the proper test equipment check the charging system.

Nohippychicks

Pulling that cable while the alternator is running can also burn out diodes in the rectifier. And a rectifier that doesn't rectify is...junk.

Grab your multimeter. Check voltage at idle at the battery posts on nice, clean metal.

While running, you should have at least 14-ish volts. If you do not have at least this reading, do the same check from the charge stud on the back of the alternator couple of grounds, one being the case of the alternator and the other being NOT the case of the alternator, but both being clean metal.

These tests will help narrow down a few things; checking at the battery posts (not the clamps) will tell you if there is any voltage getting to the battery...if it's not, moving up to the alternator stud will help figure out where the failure is. Checking voltage from the charge stud to a ground then to the case will help determine if it may be a grounding problem, since the alternator grounds through it's mounting points.

It wouldn't hurt to post up the results of your testing as well.

Careless00045

I did the battery test, and it shows 12-ish with and without the engine running .
About the alternator test! what reading i should be expecting in both cases as if the alternator is or not the problem.
Thanks man.

Art161

With the engine running and all accessories off, a good alternator should read 13.5-14.5 volts across the battery posts.

Eismann

I feel that you are going to need an alternator based off of what you have told. I sell batteries for a living, if the car is running and the battery is still reading 12-12.8 volts (whether you have accessories running or not due to the electrical demands of the newer vehicles) then you will need a new alternator. Art is right, it should be reading 13.5-14.5 volts when the alternator is operating correctly.

Nohippychicks

Checking directly at the alternator charge stud to the alternator case or other good ground should give you a little over 14 V at idle. If you have the same reading there as at the battery terminals, it's unlikely that you have any issues with the cables or any fusible link that you may have and points to the problem being with the alternator itself.



Good luck with it!

Careless00045

I did all the mention checks above and it was obvious that the alternator was long gone, Last night i bought one from Auto parts! brand name ( tough one) 135 AMPS. i hope this will last, anyways it comes with lifetime warranty .
I installed it and all readings seems to be great ! So far so good.
Thanks to all

Nuke

There are a lot of posts regarding the OE alternator being a weak link in the S197's electrucal system. Let us know how the new alternator turns out.