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Discussion Starter · #1 ·
Hi
I have a 2012 C-Max and I have had a new battery fitted in Sept 2021 after the red battery light came on. In January 2022 just 4 months later the red battery light came on again so I had a new Ford alternator fitted. 3 months later the red battery light came on again and now its been in the Ford dealership garage for nearly 3 months as they say its an ecu problem and can't get an uncoded ecu.
I do have some understanding of circuits, voltage current and resistance and having read all the other posts on this problem, please could I ask what other members think to this?
My car is probably only worth around £3000 and to have to pay for the estimated cost of a new ecu from Ford £2000 I I am not sure this is the right way forward.
I would like to ask the Ford garage questions about the engine but I dont know where to start.
Ideally I would need to make a list of questions to problem solve, such as
1. What is the battery reading when the engine is off?
2. What is the battery reading when the engine is on?
etc
I would be very grateful for any help here, thanks very much:)
 

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Hi Tracy,
A healthy battery should show 12.6v on the voltmeter - everything turned off . With the engine idling, that should go up to 13.5v - 14.8v - telling you that the alternator is doing it's job. With the engine idling and as many electrical accessories turned on as you can - you should still be getting in between 13.5 and 14.8v - telling you that the alternator is really doing it's job.
You've told us that your car is at a main dealer, but you haven't told us whether there has been a problem with it starting and holding an electrical charge, or if it's simply about the red light that won't go out. If it's the latter of the two, then maybe you're just going to have to put up with the light - bearing in mind the cost of the ECU , and the value of your vehicle . It shouldn't be an MOT issue - but check. Let us know the outcome
 

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Discussion Starter · #3 ·
Hi Tracy,
A healthy battery should show 12.6v on the voltmeter - everything turned off . With the engine idling, that should go up to 13.5v - 14.8v - telling you that the alternator is doing it's job. With the engine idling and as many electrical accessories turned on as you can - you should still be getting in between 13.5 and 14.8v - telling you that the alternator is really doing it's job.
You've told us that your car is at a main dealer, but you haven't told us whether there has been a problem with it starting and holding an electrical charge, or if it's simply about the red light that won't go out. If it's the latter of the two, then maybe you're just going to have to put up with the light - bearing in mind the cost of the ECU , and the value of your vehicle . It shouldn't be an MOT issue - but check. Let us know the outcome
Thank you very much for this, it is really helpful!
I have made notes on what you have said and I am going to go back to the garage for further clarification on the issues with the battery and alternator,
You have given me a way forward and I am so grateful.
I will let you know what the garage say next week...
 
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