French railway signalling help. Please?

I am trying to replicate TVM-430 (Transmission-voie-Machine) cab signalling used on High Speed 1 (CTRL) UK line and on french high speed lines. Instead of signals it has signs after each passage, sensors it either changes the screen decal depending on the speed limit or signal ahead. Well i think i scripted it well but it doesnt switch the screen in NXTransit Class 153. No matter any way i edit it, it is enabled also. The model is in my profile. Here's the script:

print("WAZZAP")
local debounce = false
function onTouched(part)
    if debounce == false then
    if part.Name == "TVMMagnet" then --Change this to the name of the correct part that trips the sensor
        debounce = true
        script.Parent.Parent.Train.Train1.TVMonitor.Decal = "http://www.roblox.com/asset/?id=422347420"
        wait(1)
        debounce = false
        end
    end
end

script.Parent.Touched:connect(onTouched)

The magnet is welded to the train and it doesnt fall and moves good. The URL isnt below the script.parent.parent.train.train1.tvmonitor.decal =, Just size. NXTransit is a experimental train, i originally made it for use on StuffLoveThings's train that is a Class 153 by VTPendo. Please help anybody, nothing works?