Hello,

The battery light on my 2007 fiesta 1.4tdci came on. I checked the voltage at the battery with engine running and was getting 11.8v. I checked between the terminal on the alternator and the alternator body and got the same result. Yesterday I fitted a new alternator but the battery light stayed on. I checked the voltage and was getting the same as before but when I rev the engine and then let it idle it goes up to 13.6 v with the battery light on (it does not change when I put load on like fan, AC rear screen) - I noticed the front heated screen is not working now! I plugged in my code reader (Autel 319) but there are no codes but I did a reset anyway and the battery light went off for around 30 seconds but then came back on. Now the exclamation symbol on the code reader is lit but I'm not sure what that means. I checked that there is voltage on the control wire that plugs into the alternator.

Could anybody shed any light on this problem - faulty new alternator of wiring problem?

Thanks

Does your alternator have the 'free wheeling' type pulley ?

Is the small 'charge' controller connector fitted to the alternator and is the connection good ? These small connectors often have corroded contacts inside.

If the voltage measured at the battery terminals with the engine running is constant at 13.6V and doesn't seem to change with engine speed then the problem is most probably with the small connector.

12 hours ago, unofix said:

Does your alternator have the 'free wheeling' type pulley ?

Is the small 'charge' controller connector fitted to the alternator and is the connection good ? These small connectors often have corroded contacts inside.

If the voltage measured at the battery terminals with the engine running is constant at 13.6V and doesn't seem to change with engine speed then the problem is most probably with the small connector.

Thanks for the info. I found a broken canbus wire just near the 3 pin plug. Joined this together and tested. I had to reset the codes (although none were showing on an little.handheld autel) and all is good now. Voltage slowly rises to 14.4 v on startup.

Yes that would cause the problem. No charge control of the alternator would cause it to go in to the default 13.6V charge mode.