Hi - Line

[Whisky Willie]

My retro fit seems to have hit the buffers and I am losing my hair fast.
I bought a Hi-Line unit that appears to have been upgraded from a mark II to a mark III as it still had the trimble bolted on top of the casing. It is definitely a mark III receiver I have double checked.
The television works fine, the radio is okay too, but the GPS is a problem.
In the service mode it states that I am receiving no satellite signals at all.
There is no readings of longitude and latitude and the GPS status shows ''RECERR''.
I have bought a new GPS aerial and the situation is still the same.
I also have no wheel sensor readings and the direction of travel only shows Forward. The Gyro though seems ok
I put an up to date CD in and it shows no satellite reception just the planet symbol ---- It gives the impression when you plumb a destination in that it is ok but when you call up the map it defaults to another map put in some time ago..
Can anyone take me through STEP BY STEP on how to proceed now?
I would grateful for any help whatsoever.
Rob