Cummins-Tachometer

[mdereyes]

Hello, I have a 98 Monaco Signature with a 500 Cummins N-14 Celect +. The tachometer after a few minutes gets to bouncing and goes all over the place. If anyone knows Cummins, does the tach signal come from the alternator, or does it come from the EEC? The N-14 was the first Electronic Engine Computer model, and has a history of computer problems.

Thanks for any help!

[Ivylog]

Not for sure but on that old probably from the alternator.

[windsorbill]

I have the smaller ISL, but I had exact same issue. Turned out a bad ground on the firewall, just behind the generator.

[johnhuff]

I have a 97 Cummins ISB 24 valve on a Freightliner XC chassis and it turned out to be the crankshaft position sensor $50 part and about an hour labor DIY. My tachometer was not active in the ECC but it was OK on the dash. I had low boost...