Changed foucs speedometre but car not start

Yes it is always best to disconnect the battery when doing such thiongs

posible speed sensor monter on the transmision by the fire wall

If the speedometer works but the odometer does not, the problem is inside the speedometer. Probably a stripped gear.

IF INSTALL NEW SPEEDOMETER THE ECM DONT RECOGNIZE NEW SPEEDOMETER SO CAR WILL GO IN THEFT MODE.THE NEW SPEEDOMETER HAS TO BE REPROGRAM TO THE ECM BEFORE CAR WILL START.LET THE VOLKSWAGON DEALERSHIP FIX.

is there a speedometre cable on that model if there is check at gearbox make sure connected right

Speedometer cabke from Trans break or in back Odometer (instrument dash).

if the fuse is ok. then it may be the sensor on top of transmission. if it fails the speedometer, will not work plus a few other guages. the sensor has a bunch of wires going in to it.

well i really do not no your isuses is what dose the car really do it dose not start or dose it run or what if the car sit around a lot you could use fuel stabilzer sea foam work grate and good cleaner for Eng you can get it at most car place now is the battery dead every time you come back to car is this the isuse need more info to help ase tech

the tell tail is on the hub and drum. a sensor at each location. you will see the one that is bad. it will be burnt. the speedometer does not have anything to do with it. it is a separate problem. most cause of speedometer problem is at transmission.

Yeah, i had this problem once... replace the speedometer and the whole system there.