My 95 Tbird (bought new) had an aftermarket
kill switch/keyless entry installed by dealer when purchased. The key fob still works to unlock door and activate/de-activate kill switch. It no longer locks doors. I have tried another matching key fob with same results. Where do I need to look first to correct problem? Interior power door lock switches still work as well.
Sometimes on Fords a installation tech needs to make up a relay group (using 2 to 4 of the standard 5 contact Bosch relays) very often a tech will put a fuse in the power supply circuit of this relay pack. Find your keyless entry reciever (under the dash somewhere and from the lock/unlock outputs trace the wiring looking for open fuses,of course the problem could be in the keyless reciever itself or one of the relays.
You can check for a signal on the lock wire of the reciever with a test light