the garage I take the (and I use this loosely now) beast, are both bmw technicians, they both worked at a bmw dealers one was techy and other was techy manager. and me being jus a home mechanic , I value their opinions.
according to Richard the connector that attaches to the thermostat became brittle and broke causing a short
they stripped the loom back and re did the loom with a new connector ,
I "think" they replaced the thermos as they said it was that that caused it , but on what ive just said there , I'm not sure
why would a thermostat cause a connector to break unless they were brutal getting the connector off.
ive ordered a new thermostar , will fit it myself , and report back
this has been the first car ive let some one else repair , I normally fault find and repair my own cars, ( obviously with forums) but I generally don't take cars to garages

just thought id let you know, I think this issue has been resolved now , but im not going to tempt fate :)
my new thermostat arrived yesterday, and after the pusser fan install being a disaster I thought id have a go at thisd :)
before I fitted the thermostat I measured the new sensor resistance it was about 350 ohms, I then started stripping, the top hose was hot and the bottom hose was cold .
(car had done 10 miles and temp was normal)
replaced thermostat and measured the old thermostat sensor it read 0 ohms ish
drove 60 miles no overheating , and the bottom hose is slightly warm .

just a couple of Q's regarding this

does the thermostat open fully like a normal one when it reaches temperature , or does the ecu open it partially to distribute coolant? and it opens and closes it regardless of coolant temperature

the bottom hose sensor is attached to the aux fan , when the bottom hose reaches a high state it fires up the aux fan? like secondary cooling,
now I got a feeling my ac needs re gassing , as the ac isn't that cold, would this stop aux fan firing up?
and now the Bowden cable on the centre vent wont go to 3 blue . again problem?

Cheers

Steve

just been out read codes with inpa, had a short on thermostat, so I killed that. looks like no further errors. apart from aux heating one , dunno :)
any one know how to turn the aux fan on in inpa, as it just says its off, surprisingly when I put the AC , on , it says ac compressor is off too , which is odd,
oh this is never ending :)

just been thinking..........

if the ac compressor has no gas in it wont engage the clutch, true?
if the ac clutch wont engage, the AC the aux fan wont work
if the bottom hose don't get uber hot it wont fire up the aux fan

so in theory, when I get my ac re-gassed, (dunno when or if it has been done and how much is in it) it should fire up the aux fan

ac>cooling>aux fan
cooling>normal fan>high temp at bottom hose>+aux fan

what you think trader? you seems to know more about this than I do :)
any way im off to the pub, to ponder about it ,

In inpa you get a code.I don't really remember in which menu it is,but there's a code.I had it.

Google says Code 141,but I am not sure if it's correct.