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Scott, Driveability expert
Category: Dodge
Satisfied Customers: 1190
Experience:  Dodge,Chrysler,Jeep Master Tech since 92.ASE Master since 1990.Currently Dealer employed.
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Put a brand new alternator on the car and it wont hold the charge

Resolved Question:

just put a brand new alternator on the car and it won''t hold the charge
Submitted: 9 years ago.
Category: Dodge
Expert:  Scott replied 9 years ago.
Hello, Do You have a test light? or meter to aid in testing? Thanks, Scott.
Customer: replied 9 years ago.
no and perhaps I worded my original question wrong, I should have said the alternator won't put a charge into the battery.
Expert:  Scott replied 9 years ago.

I did understand. This problem can be caused by poor electrical connections at the positive battery , or the starter power connections. Look at the way the battery cables/ wires are fastened to the metal clamp that attaches to the battery's positive post. Lift the plastic cover from the positive side ( if still present ) and inspect for bright clean copper wires that are crimped onto the battery clamp. There is a red cable that then runs over to the fuse box. Its crimps should be good and bright. If the wire is whitish, like it got hot , then there is a poor connection there. I will start the car and touch the wire crimps to see if they start getting hot.Then there is a bad connection there . I will start the car then turn on the a/c - blower on hi and headlights on . You also need to look at the wires that connect to the starter . There will be 2 large wires at the main power post and a smaller wire connected to the solenoid. The alternator output is connected to the large cable at the starter. The power then runs from that connection to the battery for charging. The same problem can happen at this terminal. A loose or poor connection can cause the wire connections to get hot and stop the charging current from reaching the battery.

Take a look and please reply if the wiring checks ok, Also if the car still runs , please turn headlights on and check to see if the dim when the engine is shut down.

Thanks , Scott.

Customer: replied 9 years ago.
it is not possible to check your suggestion at the moment, it is now getting dark and we're at about -25, we will check tomorrow though. thanks for your time, will you be on tomorrow?
Expert:  Scott replied 9 years ago.
Yes I will be here . I hope you understood what to look for. We need to ensure good connections . The head lights on a normal charging system will dim when the motor is shut off, And will brighten up after a second or two starting . Its warm and sunny here in the desert southwest. Have a good evening., Latter Scott.
Customer: replied 9 years ago.
Thanks, XXXXX XXXXX back to you tomorrow. Where in the desert southwest are you? We're in Newfoundland
Expert:  Scott replied 9 years ago.
Phoenix Arizona. Latter
Customer: replied 9 years ago.
Sorry it took so long to get back to you. My husband couldn't check the wiring himself so he took it to our local garage and has literally spent the day there. They checked every possible wire and found nothing. The mechanic took off the new alternator and is returning it. Nobody seems to be able to figure out why the alternator is not charging the battery. Any ideas? We're at our wits end here in Newfyland.
Expert:  Scott replied 9 years ago.

hello. The charging system is fairly straight forward. There are two electrical parts of the charging system. Lets call them power and control. The power side consists of the alternator output terminal, the wiring to the the starter "B+" and the wiring to the positive battery terminal. The ground for the alternator is provided by the connection to the engine.

The control side has two wires, One runs straight to the engine computer and the other is supplied 12v when the engine is running. The computer provides the ground circuit for the control side. The common problems are ( not in order of failures) , broken wiring at control side of alternator, thats the two wires that plug in. The engine computer failure. Battery connections at the starter post or the battery cable to clamp connection.

One way to test the system is to use a test light. There has to be 12 volts-Bright light - at the large output power connection at the rear of the alternator.

The alternator case should provide ground when a test light thats connected to positive battery and touched to the alternator case.

The next place to test is the control circuit. The computer energizes 12v to the green with orange stripe wire when the engine is running. The test light should be bright when connected to this wire -with the engine running. The other wire - green -is grounded by the computer to provide the charging control. The test light will glow when its connected to the positive battery and the green wire at the small alternator connector.

You can also connect the test light to the GR/OR wire and the GR wire. This will glow when the engine is started.

A few notes: The computer needs to "sense " the alternator control circuit- before it will turn the control circuit on. Simply said, If the wires are broken or terminal loose- the computer may not energize the control circuit. When the test light is used to test the circuits, It has to be connected to the wiring before the car is started.. The computer will think the test light is the alternator and act normal.

The terminals of the alternator connector can be damaged if probed with the end of the test light. We use some stranded wire to engage and make the connection with the small terminals of the connector.

We normally find a broken wire right at the alternator connector. An easy way to check is to hold the connector and pull on each wire and check to see if it stretches. If it does then that wire is broken. The connector can be bought and replaced, and the terminal /wire connection can be repaired if your careful.

I hope this helps. If you need more help. please reply.





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