C5 Sat Nav

[shsd]

:blink: For any one interested I have fixed my Sat Nav (C5 2001) The problem showed itself by the Sat Nav positioning the car approximately 30 miles out of position. (see satnav lost at sea). After investigating the CD and software I concluded that the problem was the incoming GPS signal. To test this I checked the geographical infomation display (thanks randombloke) this is supposed to read a signal strength of 3. Mine was reading 1. So the antenna was suspected. To test this I needed a good antenna. As the problem could be either the GPS unit or the roof mounted antenna or the connections in between the two.

Step one check continuity of cables. Remove the two screws securing the CD unit lift up the compartment door to ease out the unit. Remove the aerial plug (SMB connector) from the back of the unit. Drop the headlining above the rear seat to expose the connector plug. The GPS conn is the grey one.

Step two connect a known good antenna (more later) to the CD unit go for a short drive to establish signal (Check signal strength etc.)

 

This will determine if the problem is the roof base unit or the GPS module.

 

In my case it was the roof base unit.

 

Replace roof base unit with a new one.

 

Note: The GPS antenna is not connected to the radio aerial but is a separate module inside the base unit. The base unit containes three separate modules 1 radio 2 Traffic master 3 GPS. The radio and traffic master are powered by a 12v supply (red wire going in) The GPS module is probably powered by a 3.3v supply fed from the GPS module via the antenna wire.

 

To get a known good antenna I purchased a cheap plug-in module from Maplins electronics £9.99

plus the correct SMB connector for the rear of the CD unit. These units are used in cars when after-market SatNavs have reception problems.

 

On connecting and testing this system my unit relocated the car correctly and signal strength returned to 3. Problem solved!!

 

On buying SMB connectors; unless you have a crimp tool of the correct type buy a clamp type connector.