Control Unit problems

[cesevs]

Hi,

Have ,sat nav probs, on S320CDI 2004 model, had new aerial fitted, lattitude and longitude still out, so has me in Norwich, when nowhere near. Merc dealer thinks may be Control Unit, MA2118708926/80 part number. Did swap one in, which meant Sat Nav worked, when they originally thought it was aerial.

Anyone else had this and any thoughts/solutions?

Thanks,

Ceri