Strange problem

[Jesske]

Last week:

When I touched the brake, used the sidemarks, put the car in reverse, ...
the light of the rear foglights came on on the dashboard.

Today:

When I touched the brake, used the sidemarks, put the car in reverse, ...
my radiolight and aircopanel was fading

What's happening?

 

[16v_jon]

Bad Earth mate

 

[Jesske]

That's what edde also told, but where do I find the bad earth?

 

[Jesske]

It started after I installed my GPS MS 3200.
I took the ground for the GPS under the dashboard.
I tried to search the wire to connect the reverse function. I was not able to find this wire? unplugged a rearlight and took a tool to find out the reverse wire. I know for sure I had little short circuit there. Can this be the problem?

 

[Adamhodg]

If you've removed the rear light(s) you will need to clean the contacts. spray wd40 on them.