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350matt, Engineer
Category: Mazda
Satisfied Customers: 20396
Experience:  Mechanical Engineer BEng Hons22 years experience
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Mazda 6:

Customer Question

Submitted: 6 months ago.
Category: Mazda
Expert:  350matt replied 6 months ago.
Hello you don't say what model and make this is but 1st check that the alternator is actually charging the battery in the car by taking a battery voltage reading with the engine off then another with the engine running. The 2nd reading should be higher than the 1st and climbing steadily. And also check that the alternator is secure to the engine as this provides the ground for the charging circuit and make sure that the engine / gearbox earth strap is secure and the contacts are clean and bright. if the alternator appears not to be working - take it to a electrical specialist and ask them to test it as sometimes you can replace just the diode pack and this will repair the alternator without requiring replacement And one last thing is – how old is the battery? – As even good quality ones need replacing every 5 years and faulty battery just won’t hold a charge
Customer: replied 6 months ago.
Its a Mazda 6
Customer: replied 6 months ago.
The battery is about less than a year and I had the alternator changed less than a year ( I found out later than I didn't need to change the alternator, it was the battery in the first place)
Expert:  350matt replied 6 months ago.
Ok but is the battery charging up in the car?as its quite possible that both battery and alternator are fine but a broken sense wire that runs from ECU to alternator will prevent it form ever switching onto charge
Customer: replied 6 months ago.
When the check engine light went on, the first mechanic I went to run some diagnostic and here are some of the codes he got: p0600, p213, p2101. When I took it to another shop they told me that the battery was in 12.5 charge so he told me to leave my car to have it fully charge for one hr, he told me there's no code that came up, but then the light still goes on and off.
Expert:  350matt replied 6 months ago.
hello to get those codes means the ECU has lost communication with other car modules so I'd next check the condition of the ECU fuses and power relay for corroded connections or signs of overheating
Expert:  350matt replied 6 months ago.
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