The RAC module and the door switches for the locks trigger the lock relay on parallel circuits. If neither work there must be a fault in the power to or from the relay. There should be 12v on the orange wire to the relay. The white wire triggers the unlock side of the relay, the lite blue wire triggers the lock function. The tan is the output to unlock the doors and the grey is the lock. It should work with the door switches regardless of the RAC. Maybe there is a weak ground on the black wire from the relay that opens up when cold. You can check this with a test light.