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Jim, ASE Certified Technician
Category: Car
Satisfied Customers: 1317
Experience:  California smog licensed, ASE ceritied in L1, A6, A8 for over 30 years professionally
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I have a 2003 Mitsubishi montero sport that I have put two

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I have a 2003 Mitsubishi montero sport that I have put two brand new alternators and a new battery but it ran the battery down. Ive replaced the alternator fuse or relay but didn't help
JA: How many miles are on the car? Has the car been starting normally?
Customer: It has 126,556 and it starts just fine
JA: Are you fixing your Montero Sport yourself? What have you tried so far?
Customer: Im doing it myself and ive changed out 2 alternators, 1 new battery, all power related fuses and relays.
JA: Anything else you want the mechanic to know before I connect you?
Customer: That's pretty much it

We have a possiblity two things happening, the first is the alternator is not charging the battery or there is a drain on the battery.

Have you checked to see if the alternator is charging?

Customer: replied 7 months ago.
I went to O'Reilly and the computer couldn't check if it was or wasn't

Do you have a volt meter

Customer: replied 7 months ago.
I dont

The first thing we need to do is find out if the alternator is charging the battery if not the following test need to be done.

Check the voltage at all 3 of the wires at the alternator with it running.

The S and L terminals should have over 10 volts and the output post should have the same voltage as the battery.

The L terminal of the alternator is grounded by the alternator until it starts charging and then should go to B+. Unplug the connector and check for near battery voltage on the wire with key on. Verify that the charge indicator light comes on when the wire is grounded. This circuit "excites" the alternator to start it charging.

If the alternator is charging we will need to look for a drain on the battery.

Hope this information is helpful, please accept my answer and leave a positive rating before leaving the site.

Do you need further information?

Customer: replied 7 months ago.
Im testing the alternator right now and it is a good one. It passed the testing

How was it tested? What was the battery voltage during testing?

Customer: replied 7 months ago.
I took it off and tested just the alternator

It needs to be tested on the vehicle to make sure there is not a wiring problem to the alternator.

Customer: replied 7 months ago.
My battery voltage is 9.59
My alternator voltage is 7.81
Customer: replied 7 months ago.
The engine shut off right after I I test the voltage on battery and alternator. I had to jump start it and took cables off before I did the testing

The battery needs to be fully charged and then preform the test, I sent you.

Customer: replied 7 months ago.
I think im just going to replace the wiring from alternator to battery

Try charging the battery and do the test I sent you.

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