Erratic RPM indication

[Stu McCurdy]

I had a similar problem early on with my AFS 5500 with wandering tach indications. Finally traced it to the ends of the blue electronic ignition leads where the center carbon wire folds over on top of the blue insulation before clamping on the snap connector to the plug. Too tight a bend will break the carbon leaving a minute gap, not enough to cause misfiring, but enough so the impulse is raised so high to jump the gap it puts out a huge EMP. That gets picked up by the AFS 5500 RPM sensor and caused small erratic jumps. I found the problem by checking the wire continuity. I solved the problem by using an awl to role the carbon wire around to the top of the blue insulation before clamping the connector. Continuity checked good and no more erratic RPM indications.

[dhmoose]

Originally Posted by Jesse

I saw almost he exact same problem. AFS had a system to "filter" the signal and the problem hasn't returned.

Jesse - I haven't heard of this. I'll ask Rob at AFS about it. Thanks!

Originally Posted by Stu McCurdy

I had a similar problem early on with my AFS 5500 with wandering tach indications. Finally traced it to the ends of the blue electronic ignition leads where the center carbon wire folds over on top of the blue insulation before clamping on the snap connector to the plug. Too tight a bend will break the carbon leaving a minute gap, not enough to cause misfiring, but enough so the impulse is raised so high to jump the gap it puts out a huge EMP. That gets picked up by the AFS 5500 RPM sensor and caused small erratic jumps. I found the problem by checking the wire continuity. I solved the problem by using an awl to role the carbon wire around to the top of the blue insulation before clamping the connector. Continuity checked good and no more erratic RPM indications.

I'm running dual mags but I wouldn't be surprised if it's not the sensor but rather, some electrical gremlin causing the issue.