Alternator Change

I have to change the alternator. Never did it before.
In the box, on instruction: “Charge battery to at least 12.6V or Alternator Death will occur.”
I checked the battery; I have 7.5V or 7.8 with the engine on. I checked the battery on my other car, year 2004, still have just 7.5V.
Can I change the alternator with 7.5V battery or I have to buy a new one.
On the Repair Manual for my car is nothing about voltage when you change alternator.
Please help a rookie in cars.
Thanks a lot.

I have to change the alternator. Never did it before.
In the box, on instruction: “Charge battery to at least 12.6V or Alternator Death will occur.”
I checked the battery; I have 7.5V or 7.8 with the engine on. I checked the battery on my other car, year 2004, still have just 7.5V.
Can I change the alternator with 7.5V battery or I have to buy a new one.
On the Repair Manual for my car is nothing about voltage when you change alternator.
Please help a rookie in cars.
Thanks a lot.

Sounds awfully low voltage check all your connections, see if there is enough fluid in the battery and be sure its charged up. check that the alternator belt isnt slipping and its connections are good then if all that is ok the check the following

To check for battery drain:
a. Key "off", disconnect the (-) battery terminal. Connect a test light between the (-) battery terminal and the disconnected battery cable. It the light comes on, there is a short (drain) somewhere in the electrical system.
b. Disconnect the alternator wiring harness. If the light goes out, there's a problem in the alternator, and it should be replaced.
c. If the light stays on, pull each fuse until the light goes out. (This will tell you which component is shorted.)

I went to a electrical shop and they told me I have a problem w/ alternator.
But the question is, can I change it w/ this battery or I need one w/ 12V?
Thanks

I went to a electrical shop and they told me I have a problem w/ alternator.
But the question is, can I change it w/ this battery or I need one w/ 12V?
Thanks

Alvin could answer it better but consider how old the battery is if you dont remember then its proberly time to replace. Sometimes there is a stamp or hole punched that tell you about how old it is. However if it isnt old you may be able to check the water (you proberly drove a little without the alt. working to its fullest and possibly drained the battery). charge the battery.

I try anything before I spend money. But you'll proberly should shop around just in case

I have to change the alternator. Never did it before.
In the box, on instruction: “Charge battery to at least 12.6V or Alternator Death will occur.”
I checked the battery; I have 7.5V or 7.8 with the engine on. I checked the battery on my other car, year 2004, still have just 7.5V.
Can I change the alternator with 7.5V battery or I have to buy a new one.
On the Repair Manual for my car is nothing about voltage when you change alternator.
Please help a rookie in cars.
Thanks a lot.

If your meter shows voltage that low and either of the cars you checked will start......the meter is un-reliable, reading incorrectly.

The battery not fully charged (either discharged or has a bad cell) will cause the alternator to overcharge and could burn it out. That is the reason for the caution. Get a reliable meter and recheck the voltages.
Fully charged battery.....engine OFF should be approx. 12.6V.
Fully charged battery.....engine ON and running approx. 2,000 RPM should read 14 - 15V. (with good alternator). Get back to us if you need any help.

Thank you so much guys.
1) I used a different voltmeter. I got 12.3V.
2) I checked for a battery drain. Got a 1.9 amps. When I removed the horn fuse 0.00 amps. Fix it.
3) I was told to recheck for a short in this way: with the battery connected, pull out a fuse (horn), suppose to have no voltage. I got 12.25V. IS THIS A CORRECT way to check for a short ???????
Thanks again,
John

Thank you so much guys.
1) I used a different voltmeter. I got 12.3V.
2) I checked for a battery drain. Got a 1.9 amps. When I removed the horn fuse 0.00 amps. Fix it.
3) I was told to recheck for a short in this way: with the battery connected, pull out a fuse (horn), suppose to have no voltage. I got 12.25V. IS THIS A CORRECT way to check for a short ???????
Thanks again,
John

im not good with it but does sound like something is gounding out. alvin will know more

Thank you so much guys.
1) I used a different voltmeter. I got 12.3V.
3) I was told to recheck for a short in this way: with the battery connected, pull out a fuse (horn), suppose to have no voltage. I got 12.25V. IS THIS A CORRECT way to check for a short ???????
Thanks again,
John

O.K. the 12.3 sounds better, slightly discharged but nothing to worry about.

To check for battery drain (short):
Turn off all accessories in the car. Ignition switch 'OFF'
If you have a under the hood light and it's working properly...remove the bulb.
Disconnect the (-) battery cable. Put a trouble light in series with the (-)
battery terminal and the battery cable. The light may glow dimly or flash.
The flashing is the onboard computer memory, radio memory and is expected. If the light is brighter and steady would indicate the possibility of a short or something like a glove box light, trunk light etc. not shutting off.
If you have doubts, replace the trouble light with your ampmeter. There should not be more than 0.5A draw. If is 0.5A or less, current drain level is acceptable, re-connect (-) cable to battery. Car is ready to start.
If there is more than 0.5A draw , disconnect the alternator check the amperage if it remained the same the problem is elsewhere. Reconnect the alternator. Now you pull the fuses one at a time until the amperage drops. When it does, you have found the circuit with a short.
If you have any questions or need help, let us know.