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Matt, Engineer
Category: Classic Car
Satisfied Customers: 20381
Experience:  BEng Hons mechanical engineering 20 years repairing my own cars and others, 8 yrs in formula 1 engin
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Red gen will not go out after engine is stared

Customer Question

red gen will not go out after engine is stared
Submitted: 1 month ago.
Category: Classic Car
Expert:  Matt replied 1 month ago.


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

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