My 2000 SuperDuty has an odd issue. The battery/charge warning light flickers around 1800 RPM and then stays on at 2000 RPM and above. The reverse is also true i.e. it flickers when I go below 2000 RPM and goes out at 1800 RPM.

Anyone have any clues? (I know this is not a diesel-specific issue, but nobody on the other forums seem interested in hepling with ANY issues if the truck is a diesel)

 

Mine did the same thing and replaced the alternator and fixed the problem. Tested ok at the parts store? First make sure all your battery connections are good and pulleys/ belt check out. Also, I would recommend getting a gator belt.

 

Yea, replaced my alternator and it fixed the problem as well. I even went as far as replacing the wiring plug on the alternator itself. My alt checked out good ON the truck but not when I took it off. Light hasnt flickered or come on since the new one though.

 

Exactly!! even up to the point of the Gator belt.

 

They have you covered, Voltage regulator is going out. replace alt. , and check batts. If this issue has been happenign for a while (months or a few thousand miles) then you may need to replace the batts too.