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Repair Guide for the 2004-2008 Mazda RX-8. A Japanese sports car built from 2003 until 2008.

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My battery light came on in the dash and would blink on and off I have

My 2004 RX8 standard shift rotary engine the battery light came on on the dashboard and I don't know why

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Hi @wendyanne27695

The battery light is indicating that the alternator is not supplying the correct amount of voltage for the vehicle's electrics e.g. keep the battery charged and supply power to the rest of the vehicle's electrics (as required) when the engine is running.

Check for the following possible causes with the vehicle parked, the handbrake firmly applied and the transmission in Neutral (MT):

  • loose alternator/waterpump belt (aka drive belt).

Check that the alternator belt is OK and not loose i.e. correct tension etc.

Block Image

Block Image

(click on image)

  • faulty alternator (or voltage regulator - inside the alternator)

Start the engine and then connect a voltmeter across the vehicle's battery terminals. You should measure between 13.8V-14.5V DC with the meter. If not and the alternator belt is OK there may be a problem with the alternator or the voltage regulator (which is inside the alternator) Be safety aware if you do this as the engine is running

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Wendy anne crwdns2934231:0crwdne2934231:0
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