Our Cherokee 180C has a similar red arc due to the type of prop we have on
it (can't remember type) for vibration issues. We could put a different prop
on and have the red arc removed. $$$$$$$$$$ Ugh. BRBR

The red arc on the Cherokee is from the Sensenich prop on any hollow crankshaft
Lycoming, namely the O360-A3A engines.

The solution, which was around 1967 and up was a switch on the Cherokee 180's
to an O360-A4A, which has a solid crank and is green arc all the way.

It sounds very suspiciously like the tach from a Cherokee was installed in the
Archer.
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Dr. Nuketopia
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