/\ yes your diagram will work for what i want.
i choose the pressure sensor method because i know for a fact then that the fan will only come on once a boost signal is detected. leaving the ignition and starting side of the car free of electrical fan load.
time delay switch will work but only one flaw. if you leave the key in the ACC position and are fiddlign around with something (like maybe checking error codes) the fan will come on when the timer is triggered.
 
anyway ill see what i can come up with soon.

that reminds me it seems silly to have my Davies craig running all the time in winter - time to plug that sensor in, the E85 keeps things cool anyway lol

I have a DC fan running on stock wiring and it's been fine for a good 18months or so, so not sure what the issue is there. Heck I even soldered it myself (not a pro job). Why don't you just invest in a better battery if your worried about starting issues? As far as the rain shroud goes - I'd personally much rather have a **** load of hot air being taken out of the bay than try and keep a bit of water out. The only things the water has affected me with is the plugs on the ign leads don't seal very well...well 1 in particular and TWICE only has water gotten into the plug well and yes it does get a bit dirty.
 
I have 2 gauges running opening ceremony, DC fan on stock wiring (runs ALL the time), 2 11" SPAL fans running at full tilt, power steering and all the rest of it running by the time I have my ACC turned on - never had an issue.
 
My reasoning for keeping the sidemount fan running constantly is because I don't necessarily trust the amount of air that goes through the side vents is enough. Which was indicated to me a few times after a hose down and a 40km trip and I still had water drops on the vent louvre, quite alot - and everything else was dry.

fans in the engine bay will have negligible effect on the engine taking longer to come up to temp, unless we are talking the original beetles here??!!
 
If you are really worried about water on the motor, just fit one decent fan on the lhs above the gearbox.  make sure you shroud it.

Thanks guys iil look into this soon.
might bridge the fan ECU wiring and see if that solves the problem first, then try the pressure switch or time delay and see if that works.
 
cheers

you mean run a new relay.

battery starts the car fine, but i just didnt want to kill the damn thing early due to robbing power. the volt gauge give me a warning if i leave the stereo runnign (2 amps and HU) after the car engines been off. so the fan will only make it worse.
i dnt have a problem getting a new battery.