Ford Transit, 2002, 2.4tdi duratorq starting problems!

Hi All,

I own a 2.4tdi Duratorq, 2002 ford transit. Last winter year i had problems starting the van, with the starter motor clicking when trying to start and the alternator light coming on and off when she started. i replaced the starter, rewelded the earth cable connection from the starter to the chasis and replaced the earth cable and after that i replaced the battery and alternator, new belt tensioner and drive belt. This eventually solved the problem. This winter during the cold morning i have come to the van and the battery is flat, with the starter motor ticking again. When i charge the battery >12.5v, she starts up but the lights dim and go bright for 30 seconds with the alternator light flashing on and off again. After 30s everything is normal again.

I went to halfords and got the battery and alternator tested and they say it fine, no problems. But obviously there is a problem somewhere, but i have run out of ideas to solve it. It only happens when its s cold night, that seems to be draining the battery.

Any ideas what to do to solve it the problem?

Thanks,
KJ