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I have a 1989 Civic DX Hatchback with the 1.5. Brought the alternator to Pepboys and it tested good. Bought a new battery. Put the alternator and new battery in. Drove to Pepboys again and had them test the alternator in the car. Tested good. Somehow the juice from the alternator isn't getting to the car. According to the voltage meter the voltage keeps dropping as I drive. I drive for half an hour and the voltage went from 11.5v to 10.7v. Then I pulled the positive terminal off the battery and the car shut off which it shouldn't do. AND the battery warning light is on. When I rev the car up the light goes off then comes back on when the rpm's drop.*Also all the fuses in the car are good. What's my next troubleshooting avenue? Thanks in advance.

 
Rep Power: 244

Are you taking your voltage reading from the terminal of the alternator? Your belt could be slipping.

 
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The voltmeter is connected to the battery terminals. How do I test the belt to see if it's slipping? How do I know how much tension to put on it?

 
Rep Power: 244

You have to inspect the belt for cracks. I believe it shouldn't have more then a half of inch play up, or a half an inch down but I am not certain. Usually it will squeal if it's slipping. Since the voltage is dropping it sounds like your alternator is bad, even though they tested it for you. If you are getting the proper voltage from the alternator terminals then I would say its not reaching the battery.

 
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The belt is good and is spinning the alternator. The voltage at the alternator terminal is 11.4 volts.

 
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Took the whole engine wiring harness out of the vehicle. Checked every inch of the charging wire, all good. Ima put it back in and start the car with the charging wire disconnected and check the voltage at the alternator terminal. I checked it before but with the wire connected. It had the exact same voltage as the battery which makes sense. It was probably reading the battery voltage.

 
Rep Power: 244

Your alternator is bad if its only putting out 11.5. It shouldn't match the alternator cause the alternator should put out more voltage to charge the battery. Usually around 14.5v. The alternator runs the car after it is started. Since you disconnected the battery and the car shut off your alternator is not working properly.

 
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Exactly what I was thinking. I'm ordering a 170amp from Alterstart so I can put my stereo in. Then ima put my foot up someone's a$$ at Pepboys. TWICE they checked it and said its good.

 
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The new alternator and Optima yellow top I bought will have me set for years. And of course ima do the big 3.

 
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Definitely the alternator. I disconnected the charging wire from the battery and put a voltmeter to the alternator terminal and it was only putting out 1.3 volts. Im sueing Pepboys.

Thanks for your input everyone.