Re: engine convertion

[golfmad]

hi guys as u all no im putting my b4 1.9 tdi p reg engine into my h reg b3 passat right both engines are out i no theres a few air pipes goin to the turbo etc and switches etc ive found today while takein air pipes of that on the pass side wing inside engine bay theres a switch with a air pipe that runs threw bulk head and gos to a little conecter on the heater matrix i dont have this on the b3 matrix can sum one explain what its for cheers