While I've got the interior out of my car(89 5.3), should I add some additional earth wires and if so any suggestions where ? Thanks in advance once more

 

The only really important thing, with the exception of the instrument cluster, is to grind EVERY earth connection on the body to bright metal; BOTH the connector rings on the loom and the body itself. Then attach the earth, then squirt some white grease over the lot. You will see many earths on the tunnel, and on the upright bracers each side of the aircon unit. Also, brighten up ALL the rubber loom connector plugs and use electrical connector cleaner in an aerosol with a toothbrush on both sides before reconnecting. I did this 10 years ago and everything works as it should. Do this throughout the car, particularly on the earth connections to the body down by the ECU in the boot.

For the cluster, the really important thing, I have found, is to clean to bright the steel earth strap along the top of the rear of the cluster just level with the warning lights. Adding another earth here cannot hurt, but the real problem (I have found at least) is the connections to the earth strap from the flexi circuit board. It is also very easy to reconnect them to this strap so that no electrical connection is made by getting the flexible bit in the wrong place relative to the copper! (Don't ask!).

 

Thanks greg

 

Greg's correct you do not need additional earths, they can cause more problems than they solve. Clean up the metal at the earth point and make sure the connection is good. I used a tool I have kind of like a milling cutter with a pin that removes paint from the hole. After I cleaned up earths and re-fitted I applied seam sealer over the earths to keep moisture out.

 

Ok warren cheers. Nice to hear from you again.

 

FWIW I'll say that adding redundant grounds has never caused me any problems; I'm not quite clear on how they could cause a problem.

Cheers
DD

 

Because you can get a potential difference between the grounds that can induce noise and cause issues with ECU's and other electronics.

Grounding can be difficult for an experienced Technician to sort out, so I tend to err on the conservative side and keep grounds to a minimum, I also try to keep all the grounding points close together (star grounding).