Frequently Asked Question

This is caused by no tachometer signal from the engine, or by an open circuit to the tachometer signal from the engine, or an EMP that is set to 0 on a Standard (2-stroke) EIS model instrument. Check you wiring to be sure you have a good connection to the EIS tachometer input.

When using the lighting coil as a tachometer source, a failed regulator/rectifiger can short out the lighting coil and causes a loss of the tachometer signal. A simple way to see if this is the case is to run the engine and observe the battery voltage using the EIS Volt display. If the voltage is 12.8V or less, the battery is not charging. Fix the charging problem and the tachometer problem will also be fixed. The charging problem can be caused by a bad regulator/rectifier, or wiring problem between it, the engine's lighting coil, or the battery.

A simple test is to disconnect the tach wire from the engine. Using the tach lead to goes to the instrument, tap this on and off onto a source of 12V power. This should cause the EIS to show some tach reading other than zero. If it does, the EIS is most likely working correctly. (This test will not work if any tach resistors are installed in the tach lead that are greater than 27k ohm.) If you are unable to get a non-zero tach reading while performing this test, perform a continuity test (using a test light or ohmmeter) to verify the wiring from the EIS connector to the end of the tach lead is good.

Rotax 914 (does not apply to Rotax 912) The tachometer output passes through the turbo control box. The tach output from this box is polarized (although Rotax fails to note this) so that it will only work when connected in one of the two possible ways. If you do not get a tachometer reading on a Rotax 914, reverse the tachometer connections.

For Rotax 2-cycle engines, a zero RPM reading can be experienced when using the gray tach lead during the Mag check. The gray tach lead is a tap off the coil used to power one of the mags. When this mag is shut down, the tach signal is reduced, and may be unreadable by the instrument. In some cases performing the mag check at 3500 RPM or higher may allow a tach reading to be made.

Note: For instruments which include an "EMP" setting (these are model 3, 2-stroke or Standard instruments), an EMP setting of zero will cause a tach to read zero at all times. Set the EMP according to the maual (typically 20 for Rotax CDI, 60 for all else.)