faulty alternator and now ECU!!

[buggy]

original issues came to light with the cold weather and flattened battery. Had battery checked and is fine ( only 1 yr old and still under warranty). Noticed a faint whirring noise followed by the lovely burning insulation smell. The alternator had decided to fry itself and obviously not charge the system, also had a few of the spurious faults thrown up as part of the process, as these pugs do.
Replacement alternator fitted and circuit checked, charging ok, turned off and restarted after a while, not charging and flat battery, (this is still whilst at garage) they now think the ECU is at fault as the charging circuit goes straight into it as part of the circuit (info via Autodata). Sometimes when it is started it will misfire and then the charging may kick in, switch off, restart and it charges, switch off and restart and it doesn't charge.
Please any suggestions before the ECU goes off for checking?

[GrandadMonkey]

Just check that there is no fluid leaking onto the alternator. On some models the hydraulic fluid reservoir has been known to split and leak fluid onto the alternator - with disastrous results!

[buggy]

thx GM but that already ruled out

additional info : when not charging there was a distinct pulse going through the meter at regular intervals and an associated low pitched "squeak" from the ECU itself, car was running a little lumpy until it decided to kick in and charge, then smoothed out and ticked over smoothly.
All I can think of is the ECU got spiked when the alternator gradually failed, and now that has been replaced it can't cope.

[buggy]

I finally have a solution to my issues. The alternator had cooked itself nicely, and was replaced. The next issue outlined was the charge still not happening. The ECU was sent away to BBA Reman to be checked (unfortunately the Friday before Christmas so I didn't see it again until the 2nd week in January!!), it was checked 3 times by them and declared intact and okay. So it was refitted to the car, still faulty charging.
Wiring traced back to Fuse box, tested fine for continuity, but the signal was apparently not getting through to fusebox assembly. A little creative wiring from another switched live in the fuse box (with inline fuse) cured it! Charging perfectly ever since.
When the weather eventually improves and gets a little warmer I will recheck the alternator wire, I have a suspicion that it may have overheated and caused a short, but would still show as intact. I will post the result eventually, but don't hold your breath

[GrandadMonkey]

Thank you for the update on progress. Electrical issues can be difficult to get to the bottom of.