new member

[spann2007]

hi everyone im a new member
i have a vw tiguan 2.o'tdi on a 2014 plate had from new the issue is when i press the demister button when the engine is running it lights up then after a second or two it goes off
ALL other instruments and controls work fine i've checked all wiring in the boot the heating element on back window no issues
i've had a mot done and the drivers side repeater and mirror replaced as it had a crack in it and the problem started soon after that but check and no lose wires can anyone help also checked all fuses not blown was thinking if it could be a relay problem
just to add i've had it vw dealers and they said it could be the relay and they wanted around 120 pounds to replace that may not sort it
but if anyone has diagrams or were i can get them from to find the relays it would be much appreciated
i've recently purchased the relay myself but just need to now where and how to install