# Battery and break light on after replacing alternator



## Edgart (Oct 10, 2017)

I have an 06 nissan Altima about two weeks ago i had turned on the car and the battery and brake light came on I drove it a few blocks and the car lost all power but the car stayed on it drained the battery i waited till the lights turned off and then drove it back home .so i waited till the morning and it turned on but the lights were still on the car stayed on with no power what so ever i left it on for about ten min and the lights turned off and ran normal until the next morning it would do the same thing so i replaced the alternator and the battery and it worked till the next morning and started doing the same thing again and the ive had this problem for about two weeks now and each morning i have to wait till the light turn off so i can drive it normally. has anyone had this problem? I'm thinking it's an electrical problem or something


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## smj999smj (Jan 1, 2006)

If the battery and brake warning lights are illuminated on the dash, there is a charging system problem. Unless you replaced your alternator with a genuine Nissan remanufactured alternator, don't assume it's good; I've seen a lot of "brand new" aftermarket alternators and starters over the years that were no good out of the box. The charging system voltage needs to be checked with a voltmeter (I'm assuming since the battery was recently replaced, the cable connections to it are clean and tight). Static battery voltage of a charged battery should be around 12.2-12.6 volts. With the engine running, charging system voltage should be 13.2-15.5 volts (most Nissans typically charge right around 14.7 volts) with "loads" (headlights, radio, window defogger) "on" as well as with "loads off," at idle and also at 3,000 RPM. If the voltage is too high, than it is a bad regulator inside the alternator and the alternator needs to be replaced. If the voltage is too low, it could be a bad alternator, a bad warning light bulb or circuit (which we already know is good in this case), an alternator belt that is too loose, a blown fusible line to the alternator (it'll be the highest amperage fusible link in the vehicle, typically rated somewhere between 75A and 120A) and/or a bad power supply circuit to the "BAT" terminal on the back of the alternator. The circuit to the "BAT" terminal comes from the already mentioned fusible line and the wire is usually 10-gauge and white. Sometimes this wire will develop internal resistance and "burn up," making it real brittle and not allowing power to get to the alternator. You can use a 12v test light to check for power at the "BAT" terminal to check the circuit and confirm the fusible link is not blown.


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