I have just purchased a trip computer for my W126 sec
I have tried bench testing it but unable to get the lcd display on the trip computer to come on
Is it possible to bench test or do I need to connect the car loom plug as well

It is a 1984 loom I have

Brown earth

Wire which goes to x35 terminal is this terminal a 12V supply

Any help would please be appreciated as not many have done a retro fit and i am struggling to power t up on the bench