There is too much noise or it is malfunctioning.

If using contact-free, with the hour meter and the spark plug cables at a distance of 5 to 15 cm, slowly raise the RPM from idle to max RPM and check that the colon (:) on the LCD display flashes in all ranges. If using by wrapping the antenna lead, reduce the number of wraps. The normal number of wraps is between 3 & 5, but it may vary with the strength of the ignition pulse. Slowly raise the RPM from idle to max RPM and check that the colon (:) on the LCD display flashes in all ranges.