How can I make a vehicle the stops when a part is no longer connected to the rest of the vehicle?

I want the vehicle to stop working when the "required" part is disconnected from the rest of the vehicle. I tried doing so by using :FindFirstChild("Weld"), but even if I delete the welds the script continues to move the vehicle. Shouldn't the FindFirstChild return nil when I delete the welds?

--Movement variables.
local move = script.Parent
local partMoving = false
local rotation = 0
local mode = "Forwards"
local movementY
local working = true

--Part required to run.
local required = script.Parent.Parent.Require

--Variables for the buttons.
local downBtn = script.Parent.Parent.Console.Down
local upBtn = script.Parent.Parent.Console.Up
local leftBtn = script.Parent.Parent.Console.Left
local rightBtn = script.Parent.Parent.Console.Right
local modeBtn = script.Parent.Parent.Console.Mode
local ignitionBtn = script.Parent.Parent.Console.Movement

--Sets the movement mode.
modeBtn.ClickDetector.MouseClick:Connect(function()
	if not partMoving then
		if mode == "Forwards" then
			mode = "Reverse"
			modeBtn.BrickColor = BrickColor.new("Eggplant")
		else
			mode = "Forwards"
			modeBtn.BrickColor = BrickColor.new("Cyan")
		end
	end
end)

--Starts or stops movement.
ignitionBtn.ClickDetector.MouseClick:Connect(function()
	if not partMoving then
		partMoving = true
		ignitionBtn.BrickColor = BrickColor.new("Lime green")
	else
		partMoving = false
		ignitionBtn.BrickColor = BrickColor.new("Really red")
	end
end)

--Sets the movement rotation
rightBtn.ClickDetector.MouseClick:Connect(function()
	rotation = -1
	wait(.3)
	rotation = 0
end)

leftBtn.ClickDetector.MouseClick:Connect(function()
	rotation = 1
	wait(.3)
	rotation = 0
end)

--Sets vertical movement
upBtn.ClickDetector.MouseClick:Connect(function()
	movementY = .5
	wait(.4)
	movementY = 0
end)

downBtn.ClickDetector.MouseClick:Connect(function()
	movementY = -.5
	wait(.4)
	movementY = 0
end)

--Moves "Move" based on the previously set instructions
---[[
required:WaitForChild("RequiredWeld")
while true do
	if script.Parent.Parent.Require:FindFirstChild("RequiredWeld") ~= nil then
		if partMoving then
			print ("Should be moving!")
			if mode == "Forwards" then
				move.CFrame = move.CFrame*CFrame.new(0,movementY,-.1) *CFrame.Angles(0,math.rad(rotation),0)
				wait (0.001)
			else
				move.CFrame = move.CFrame*CFrame.new(0,movementY,.1) *CFrame.Angles(0,math.rad(rotation),0)
				wait (0.001)
			end

		else
			wait (0.5)
		end
	else
		ignitionBtn.Material = "Glass"
		ignitionBtn.ClickDetector:Destroy()
		ignitionBtn.BrickColor = BrickColor.new("Maroon")
		--[[for i = 0, 10 do
			move.CFrame = CFrame.new(0,-.1,0) *CFrame.Angles(math.rad(-1),0,0)
			wait (0.001)
		end
		working = false
		while working == false do
			wait(.1)
			move.CFrame = CFrame.new(0,-.1,0)
		end
		--]]
	end
end
--]]