aftermarket fuel guage

[PurpleSNow]

I am trying to wire a aftermarket fual guage as the original is broken.

 

but it shows a reading and when i switch off the alarm and the clluster comes on then it goes half tank and stayes there.

 

can anyone asist on this. I spiced the correct wire its a brown wite wire from the cluster.

 

any help would be app as im looking for the light to warn me that im low on fuel.