speedo only works with lights on

[big pants]

i have a ford galaxy my speedo only works when i put my lights also my petrol gauge goes up and down like a yoyo ford fitted a speed senser but that dint cure it can you help?

[qapmoc]

This could be due a bad/poor earth connection on the dashboard assembly, probably all the electronics is mounted on one circuit board at the back of the dashboard and if it loses a good earth connection it will affect all the instruments at the same time.

[sense4all]

Have you checked that when the speedo works it is infact acurate.... when I had a Galaxy after running the gamut of the local parish councils pseudo speed trap (they borrowed it from the county council ) I was doing almost 37 when the speedo showed 30. I got mr sense to follow me in his car and the ratio got bigger as the numbers got higher.... this was an AUTO, and used some magnetic "thingy " to form the basis of its calcs this was defective and they replaced it under warantee.But previous Galaxy had a water leak that started in the windscreen area but ended up in the footwell... another mother at school had a similar problem with water ingress, do you think that could contribute/ be a possible cause of your problem? Mine was R REG hers was S REG. both manual.On a lighter note my fuel gauge went up and down like a yo yo too, but suspect that is a culmination of my driving , living in a hilly area and crap mileage lol