456 earthing locations

Hi I have a 456 GTA 1996
I have restored the car but still have a couple of issues I have yet to sort out.
hopfully some one can help me out.
I think all of my problems are related to the same issue.
problems
air conditioning isn't working, no power to the pump
dash lights flicker
suspension adjusting switch doesn't change anything (stuck on soft)
no warning light but it doesn't change under speed etc.
when I go from high beam to low beam the highs just dim and the blue high beam light on the dash stays on but dull.
the car originally had earthing issues stopping it from starting.
im convinced that I still have a bad earth some where but cant find it.
cleaned the ones in the boot (trunk) behind the passenger airbag and under the bonnet but all where ok.
am I on the right track and can anyone tell me where some other earthing points may be.
or does anyone else have an answer for me
thanks Adrian