[rattlsnak]

Keyless Dongle? Porsche didnt have keyless entry in 1990 in 964s.

that being said,

there is three wires going to the door switches. One is permanent ground, the other two should be open circuits until you move the key to lock or unlock which then completes one of those circuits to ground. You can check this at one place at the module. Unplug the module and test pins 7 (br/bl) and 9 (br/gn) seperately. They should not be grounded until you move the key to unlock or lock. (pin 7 is lock, 9 is unlock) Confirm what is going on there and report back... and then we can continue on a path...