J.P. Instruments Classic Scanner - Manual (Page 4)

INSTALLING THE EGT SCANNER
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8) EGT and CHT Probe Wiring
The EGT SCANNER is supplied with special Teflon insulated Chromel Alumel type K wire.
Each wire is cut to length as required. Unlike most other EGT & CHT installations the probe wire
length is not critical and should be trimmed to any length as required for a clean installation.
The Temperature probes must be wired with the correct polarity. The EGT and CHT probes
connect to the temperature indicator with yellow jacket Teflon Chromel Alumel wire supplied.
Strip the wires according to drawing 5057 and terminate with the crimp-on ring terminals
provided. Verify the quality of each crimp with a sharp pull on the wire. The terminal should be
almost impossible to pull off when crimped correctly.
NOTE: The ring terminals may be crimped with a "service type" tool, however AMP part number
48518 tool is recommended. Be sure to test each crimp by pulling on the wire to insure it won't
come out. The most common installation problems are poor quality terminations.
9) Routing the Wiring Harness
Route the thermocouple wires from the instrument through the firewall using existing rubber
grommets and flame retardant silicone. Be sure to leave a small service loop at the instrument.
Following the existing wiring harness and connect to the indicator marking each lead with the
cylinder number. All wires must be routed away from high temperature areas (exhaust stacks,
turbochargers etc.). Secure Probe leads to a convenient location on the engine approximately 8
to 12 inches from the probe, being sure there is sufficient slack to absorb engine torque. It is
essential in routing the probe wire that this wire not be allowed to touch metal parts of the air-
frame or engine since abrasion will destroy this high temperature wire. Secure thermocouple
wire along the route to the indicator using original clamps, tape or tie cord if possible.
CAUTION: be sure the controls under the panel are not obstructed by the wiring.
The probe wires must not be tied in with ignition, alternator or twin engine cabin heater ignition
wires because of potential interference with temperature readings.
The probe wiring harness is made of Chromel-Alumel alloy wire that must not be substituted or
extended with normal copper wire. The power and ground wire are normal copper.
10) Indicator Installation
Locate a 2.25 diameter hole in the instrument panel or cut one per fig-1, where you would like to
mount the indicator. The SPACER, supplied, is for flush mounting of the instrument. Mount the
indicator in the panel, with or without a spacer, using the four 6-32 X 1" screws supplied. Route
the ground wire (black) to the airframe. The positive wire (red) with the in-line fuse should
terminate on the instrument panel positive buss line. An optional switch may be mounted in line
with the positive lead. The indicator is FAA TSO approved, as a temperature indicator under
TSO-C43a Record the installation of the EGT SCANNER per STC# SA 2586NM. Make entry in
the aircraft log book. FAA form 337 may be required.