Hi all. First post, so please be kind 🤪. 
Fiesta mk5 1.4d 2007. 
Battery light came on. Checked voltage, voltage low. Thought something was left on so jump started the car. Ran fine for a few days. 
Battery light came back on low voltage. Took it to local garage, said battery was fine. Cold weather hit, battery flat. Took it to have battery replaced, all fine. Battery light back on, checked voltage. Found low charge coming from alternator, replaced alternator. Now no voltage from alternator. Three wire plug on alternator. 
Things done-

*replaced battery

*replaced alternator and belt

*checked fuses in fuse box (3A in glove box, 60A in engine bay)

*Good continuity from negative terminal to alternator/engine and bodywork. 
*checked continuity from alternator plug (org wire) to positive terminal. 
 

not sure if I’m missing something obvious, but I’m now at a loss.

Any help is grateful. Thanks for any replies. 

With the smart charge plug disconnected from the alternator, what voltage do you get at the battery terminals when the engine is running at a fast idle ?

I’ve got the battery charging at the moment. It was at 12.5v no load, but when I crank it drops to 8v. 
 

Previously with the plug disconnected, still no voltage from the alternator. Battery just dropped from full charge 13.8v to 11v with car running for about 30mins. 

40 minutes ago, WayneRob1 said:

It was at 12.5v no load, but when I crank it drops to 8v.

Quite normal, so nothing unusual there.

40 minutes ago, WayneRob1 said:

Battery just dropped from full charge 13.8v to 11v with car running for about 30mins. 

obviously something not right, battery not receiving a charge.

Back to my original question:

1 hour ago, unofix said:

With the smart charge plug disconnected from the alternator, what voltage do you get at the battery terminals when the engine is running at a fast idle ?

You need to disconnect the smart charge plug and measure the battery terminal voltage with the engine running.

Hi. Started car at 12v. Engine at 2k, voltage drops down to 11.5 and continues to drop. Appears to be no charge from alternator. 

2 hours ago, WayneRob1 said:

Started car at 12v. Engine at 2k, voltage drops down to 11.5 and continues to drop. Appears to be no charge from alternator. 

If that was with the smart charge plug disconnected from the alternator then the fault is you have a dead alternator !!

.....and I know you're going to say it's been replaced but that doesn't guarantee the replacement is fully working.

A fully working alternator with the smart charge plug disconnected will always default to the standard emergency charge voltage of 13.6 to 13.8V

Thanks unofix. It was where I knew I needed to go but sometimes you just need someone to confirm your findings. Alternator removed now awaiting replacement on Tuesday (good old bank holidays). I will report back once new alternator is fitted. Cheers for your help and input. 

Fixed.
As suggested, new alternator replaced with newer alternator. Jump started car, battery light remained on. Luckily only for a few seconds and went out. Car now charges fine. Thanks for the sanity check. Heart sank when light was still on  when first started though. 👍🏻👍🏻👍🏻

I purchased a 2002 mk 5 diesel (very cheaply!) from a friend who had already replaced both the battery and the alternator but still had no charge. I bought a new alternator and paid for it to be installed. Still no charge. Car runs  (without using lights, windscreen wipers or any other electrics) for perhaps 15 miles before I need to stop, take out battery and re-charge from a mains point for the home charger. 

 

I took it up with the seller of the apparently dead alternator who strenuously insists that the alternator is new and was tested before sale to be in perfect working order. I'm not easily convinced, but what he is saying seems to have a ring of truth. He says there is an electrical issue on the mk5s that requires a specialist repair. But I cannot find the details of this online. This forum is the only search result. 

 

Any thoughts?

Gareth