Can you find anything wrong with this snippet of code? Function not executing correctly.

TmpChng (line 63.) is supposed to be responsible for the changing of the temperature either up or down based on the value "CoolantActive" being true or false.

So far it works right, when it lowers to 300 it stops which is as low as I want it to go, but when its going up is the problem.

It keeps getting stuck at 499.

Any idea why?

local Coolant = script.Parent.GUIS.Coolant.SurfaceGui:WaitForChild("TextBox")
local Status = script.Parent.GUIS.Status.SurfaceGui:WaitForChild("TextBox")
local Temp = script.Parent.GUIS.Temp.SurfaceGui:WaitForChild("TextBox")
local TempValue = script.Parent.VALUES:WaitForChild("Temp")
local Meltdown = script.Parent.VALUES:WaitForChild("MeltdownStatus")
local SelfDestruct = script.Parent.VALUES:WaitForChild("SelfDestruct")
local CoolantActive = script.Parent.VALUES:WaitForChild("CoolantActive")


function Melt()
    Coolant.Text = "MELTDOWN"
    Coolant.TextColor3 = Color3.fromRGB(255,0,0)
    Status.Text = "MELTDOWN"
    Status.TextColor3 = Color3.fromRGB(255,0,0)
    Temp.Text = "MELTDOWN"
    Temp.TextColor3 = Color3.fromRGB(255,0,0)
end

function MeltImminent()
    Coolant.Text = "MELTDOWN IMMINENT"
    Coolant.TextColor3 = Color3.fromRGB(255,0,0)
    Status.Text = "MELTDOWN IMMINENT"
    Status.TextColor3 = Color3.fromRGB(255,0,0)
    Temp.TextColor3 = Color3.fromRGB(255,0,0)
end

function OvHeat()
    Status.Text = "OVERHEAT"
    Status.TextColor3 = Color3.fromRGB(198,150,55)
    Temp.TextColor3 = Color3.fromRGB(198,150,55)
end

function PwrSts()
    Status.Text = "Generating Power"
    Status.TextColor3 = Color3.fromRGB(69,255,137)
end

function Destruct()
    Coolant.Text = "SELF DESTRUCT"
    Coolant.TextColor3 = Color3.fromRGB(255,0,0)
    Status.Text = "SELF DESTRUCT"
    Status.TextColor3 = Color3.fromRGB(255,0,0)
    Temp.Text = "SELF DESTRUCT"
    Temp.TextColor3 = Color3.fromRGB(255,0,0)
end

function CoolantSts()
    if CoolantActive.Value == true then
        Coolant.Text = "Coolant Active"
        Coolant.TextColor3 = Color3.fromRGB(69,255,137)
    elseif CoolantActive.Value == false then
        Coolant.Text = "Coolant Disabled"
        Coolant.TextColor3 = Color3.fromRGB(255,0,0)
    end
end

function UpdTemp()
    Temp.Text = TempValue.Value
    Temp.TextColor3 = Color3.fromRGB(69,255,137)
end


function TmpChng()
    if CoolantActive.Value == true and TempValue.Value >= 301 then
    wait(.2)
    TempValue.Value = TempValue.Value - 1
    elseif CoolantActive.Value == false and TempValue.Value >= 301 then
    wait(.2)
    TempValue.Value = TempValue.Value + 1
    end
end

while true do
    if Meltdown.Value == false and SelfDestruct.Value == false and TempValue.Value <= 499 then
        wait()
        TmpChng()
        UpdTemp()
        PwrSts()
        CoolantSts()
    elseif Meltdown.Value == false and SelfDestruct.Value == false and TempValue.Value >= 500 and TempValue.Value <= 799 then
        wait()
TmpChng()
        OvHeat()
        CoolantSts()
    elseif Meltdown.Value == false and SelfDestruct.Value == false and TempValue.Value >= 800 and TempValue.Value <= 999 then
        wait()
        MeltImminent()
    elseif Meltdown.Value == false and SelfDestruct.Value == false and TempValue.Value >= 1000 then
        wait()
        Melt()
    end
end