2000 D2, 165k mi, owned about 4 years. So, a couple of months ago I get a dead battery, UG says voltage running about 14.5 at start. Replace battery, still have high voltage. Always ran about 12.4-13.2 since I owned it, and that's with battery and alternator changes. Very consistent voltage, no issues. Even after new battery and new alternator recently, voltage running high and overnight battery drain. I put a ground cut out switch thingy in it. Now I'm seeing the UG blank out and reset, for no apparent reason. Where to start with diagnosis? ECU?

 

14.5v is not high -- that's where it should be when the engine is running and the alternator is charging properly.

 

 

Every once and a while I'll see my UG blank out and reset, it's done that since new...

 

 

All good points so far, thanks guys. It's the battery discharge overnight that really makes the situation difficult.

 

 

 

Now that's interesting. I've had a parasitic drain I can't find either. Eliminated SLS, charges 13.6-14.2 when driving, swapped in known good battery, and every now and then have to jump it. I carry a jump box in the back so never stranded. My ultragauge goes black when I cycle the key off... but it still draws?

 

If you can't find an obvious problem after visually looking everything over, you need to do this ^. Remove your ground wire off the battery, put a 12v test light between the neg battery post and the body. Light should light up somewhat bright in your situation. Start removing fuses one by one to see which circuit puts the light out. That will be the circuit you'll need to really dig into to find your draw.