I have the JPI EDM 900.  I used the hall sensor already installed on my magneto to feed into my JPI.  I have perfect RPM readings most of the time, but once in a while, usually after a long flight of 3 or more hours, I get wildly fluctuating RPM indications.  The fluctuations are always above the actual RPM.  They shot up above 2700 and trigger an engine warning, flashing light.  Drives me crazy.  All my connections have been checked.

 

Since it only happens after a period of time, makes me wonder it heat is an issue.

 

Any ideas?

 

Mike