Installation manual

GEM INSTALLATION MANUAL DOCUMENT No. 070906 REV. 1.4
INSIGHT
INSTRUMENT CORP. 22 BOX 122, FORT ERIE, ONTARIO, L2A 5M6
Symptom: Display is affected by radio transmissions.
Cause: Proximity of probe and/or display unit to the radio power wiring and away from radios and
antenna coax. Check radio rack connector for missing 50 ohm matching device. The 50 ohm
matching device is a thick washer-like component part that is installed underneath the connector
end cap. The end cap will have to be unsoldered to check for the matching device. This seemingly
unimportant component is supplied with all connectors and is required for proper operation of the
connector. Utilize shielded-twisted pair for power leads.
Symptom: EGT indication is not uniform.
Cause: The EGT indication for a fuel-injected engine will typically vary a bar or two from perfectly uniform when
leaned for cruise. Clean the fuel injection nozzles. Non-uniformity is normal in carbureted engines. All cylinders
are measured by the same circuitry. It is almost impossible to not have identical response on all channels of
the GEM series.
Symptom: A sudden or gradual reduction in the EGT indication can be symptomatic of several engine
faults.
Cause: Exhaust leaks above the probe and poor compression due to bad rings, valves or valve guides. If a
probe substitution does not reveal a faulty probe, check for mechanical faults in the engine. Consult the GEM
series Pilot’s Guide for more detailed engine diagnostic information.
Symptom: All EGT readings too high.
Cause: Readjust the EGT “BAR HEIGHT” on the Display. Use DVM a (digital voltmeter) to measure the
difference between the instrument ground and engine block ground with the engine running and the battery
charging. If the difference is greater than or 2 V DC with the alternator charging, remove the GEM ground and
provide an extension directly to the engine block. If this solution fixes the problem, a ground fault exists
between the engine and air-frame which should be remedied.
Symptom: Display indicates full scale or blanks out.
Cause: This can be symptomatic of an intermittent ground fault between engine and air-frame. See “All EGT
readings too high”.