I have been reading your comments on problems whereby the boat temperature gauge over-reads when navigation lights are put on. I have tried to find the faulty earth without success.
Can I simply bring a new earth wire from the battery to a new busbar on the dash and remake all the earth connections to the instruments (including the temp gauge) from that busbar? Is there anything I need to be careful of in doing this and should this cure the problem?
Your help would be much appreciated.
Your proposed solution will work great. The only concern would be the additional ground wire connected directly to the battery. I’m not a big fan of small and large wires connected directly to the battery. The connection is either too tight for the small terminals or too loose for the large terminals. If you are connecting directly to the battery, I would either put a zip tie or tape around all of the wires that connect each post of the battery to ensure that all positives stay segregated from the negatives. An accidental ground wire touching the positive will cause an immediate fire.
Hope this helps,