Electrical system squirrely Speedo wrong ??

[markmartin]

I did have some problems a coupld of weeks ago with my 94 6.5, I put a new PMD and cooler on it and the truck ran fine for a few weeks, now there seems to be some king or wierd electrical gremlin surfacing. I am hoping that it is a grounding problem, my speedo picks up about 10 - 15 mph and occassionaly the lights will flicker a little, I can run the power windows and the speedo will act up. I can shut it off for a bit and restart it and it may run fine for a while. What do you guys think? Grounding problems? What are the most likely places where the grounds get bad. I did a search on problem grounding areas, no luck, any ideas? Thanks

[john8662]

The main grounding to the cab is on the Passengers side of the engine right above the starter, you'll have to get underneath to get to it (at least on mine I did). I disconnected the connections that conneted to the frame and took some sanding paper to them just to make sure they were making good contact. Turns out I renewed the grounds troubleshooting a low oil pressure situation, that turned out to the the oil pump (I narrowed everything out that was electrical first), but this in unrelated.

I'd check the connections at the Alternator itself, it sounds like you've got a loose connector on it, or it's failing. Because you mention that when you put a load on it, that is when you're seeing the irratic speedo.

Also make sure you've got great connections at both batteries.

[charliepeterson]

Another source for grounds is the right side head in the back on top. You might find three more here.