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CarDoc, ASE Certified Technician
Category: Hyundai
Satisfied Customers: 818
Experience:  IMI L3 Motor Vehicle Mechanic
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I cannot get my Hu, Hyundai i10 2010, i cannot get the

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I cannot get my Hu
JA: What is the model/year of your Hyundai?
Customer: Hyundai i10 2010
JA: Are you fixing your vehicle yourself? What have you tried so far?
Customer: i cannot get the alternator to charge the battery properly. So far I have had a new battery from Halfords which slowly discharged over several weeks. Removed battery post and checked for leakage, alarm takes about 100ma only. Alternator replaced by local garage, battery discharges again over several weeks. Took it back to garage who then fitted official Hyundai alternator. Very little charge & battery goes flat. After charging battery over night battery voltage 15.5volts slowly dropping to steady 12.95 voly
JA: Does the battery look like it's leaking? And does it have a strong smell -- like sulfur?
Customer: 12.95 volts when starting engine voltage drops to 12.5 volts even when revving engine. Tried patch lead from alternator terminal straight to battery post but no difference. Should the alternator coil be flashed to start the charge as I have read this on other alternators? The battery is new no smell, I took the first one back to Halfords, they tested it and said it was prefect but I insisted on another one which they also tested !
JA: Anything else you want the Mechanic to know before I connect you?
Customer: Think that's it

Thank you for using JA. I'm Baz, one of the automotive experts, I try to be available in the afternoon on weekdays and in the evenings on the weekend. I apologise if I do not respond to your question promptly, I can assure you that I will respond as soon as I can. Thank you

What is the voltage at the battery post when the engine is at idle?

Customer: replied 1 year ago.
12.3 volts

That voltage is way too low, the alternator isn't charging the battery. The voltage at idle should be no less than 14.2v.

Customer: replied 1 year ago.
The alternator is a new Hyundai unit. Does the coil require ‘flashing ‘ with a positive lead to energies the field coil like some alternators?

I don't think you need to do anything like that. I would suggest testing alternator output at the alternator post and use the chassis for the ground point. If the alternator output is 14.2v or more, directly at the alternator then you have a wiring/connection issue.

What voltage reading are you getting at the alternator post?

Just a follow up, did you manage to get this sorted?

Customer: replied 1 year ago.
thank you, ***** ***** for the voltage at the alternator terminal (which I had been avoiding checking because it was difficult to get to) alternator to battery terminal 12.3 volts, terminal to alternator case 14.4 volts! Verdict; poor earth link between engine and chassis. Cleaned up connections and now have 14.4volts at battery. With modern cars, electronics and engine management units I forgot the basics; when cars were simple 90% of electrical problems were due to poor earth connections!

Good job! That is what I was trying to get to, by testing directly at the alternator. Glad you got it sorted though.

All the best and thank you for using JA!

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