RPM reads low

[rmcmurdo@telus.net]

I know this issue has been tackled for various setups but I'm hoping I can get some direction for my issue.
I've got an Lycoming IO-360 with slick mags. RPM was reading normally and then out of the blue one morning with no changes at all it won't read above 2150 rpm. Tested with a Tru Tach it's reading 500 rpm low at full power, about 300rpm low at 1500rpm and about 200 low at idle. It's the D180 with a lead off each mag. Any ideas where to start would be appreciated. Thanks

 

[Raymo]

How is the tach signal being picked up from the mags?

Not sure about the 180 but the Skyview will use the first tach signal it gets. If that goes away, it will use the other. It is possible you've always been getting the same mag signal (e.g. left) and now getting it from the other.

 

[rmcmurdo@telus.net]

Thanks. Could be. I'm going to disconnect one and trouble shoot them back and forth. See what I get.