My 75 had a leak at the exhaust fan. Water would run down and get behind the flange that mounts the motor and duct to the trailer. The putty tape that was supposed to seal it had failed after 30 years
. I removed the duct and motor and sealed behind it with a fair amount of Vulkem and reinstalled. I had to disconnect the cable that operates the door where it attached to the lever on the control panel. This allowed me to move the door out of the way to work on the duct and motor. Attaching the cable was a real PITA
. Two years later and still no leak.