I have a funny issue with my instrument cluster. Speedo is eratic, jumps around. Also Water temp needle will drop when accelerating. Seems like power being drained from cluster under load. Battery is fine, car starts first click, no other issues at all. Only happens intermittently. I suspect it could be a bad earth connection. Any ideas on possible causes? Also how is the cluster earthed? Cheers!
I believe that the speedo is earthed through one of the big plugs on the back of the speedo which would end up on the chassis somewhere. The plugs go into a 'bendy' circuit board which is made out of mylar. Could be damaged or distorted. Pull the cluster out and have a look, give all the connections a good clean and put it all back together and see if that helps.
Classic faulty speedo... I wont go into detail because there are a lot of posts on it. I recommend you do a search for faulty speedo to find the info. But basically you resolder all the points at the back of the speedo as they can develop hairline cracks over time...causing it to be erratic or to not work at all. The problem with the Water Temp could be the needle holder. I've seen some problems where the pin that holds the needle on becomes loose or isn't sitting in the right location and may need to either be replaced or 'motivated'. Hope that helps... Rob.
