"Limp Node" when air con turned on

[eza091]

I have a weird problem with my 2 door 1995 318is.. in the june long weekend floods we live on a hill- rain got under bonnet and into computer (it grew mushrooms overnight) and so dad dried it out (he knows a fair bit about this stuff) and ever since when you turn on the air con (not demist-it works) the car goes into a "Limp Node" and it comes up on dash with the symbol... How do we fix it? New computer or could the prob be elsewhere? any help would be very very much appreciated

[VMZ]

Just curious, what makes you say it's actually going into limp mode? How does it behave other than the dash symbol? Is it just the "Check engine" light or is it an actual symbol?

[eza091]

it does the *Clunk* noise, revs decrease, very hard to get up hills from a starting position, extreme loss of power... not the most ideal way to drive safely...