User guide

Engine Sensor Installation

Lycoming CHT Probe Location EGT Probe Location

EGT/CHT Installation

1. Locate the EGT probes, P/N 40200, not less than 1 1/2” or more than 3” below the exhaust stack attachment

flange. 2” to 3” is optimum, and try to mount all probes equal distance from the exhaust flanges. On curved

stacks, assume probe tip is on stack centerline for determining distance to exhaust flange. Carefully center

punch the probe hole locations such that the portions of the probes external to the exhaust pipes will not

interfere with any parts of the engine or cowling. Drill holes with a #30 drill.

2. Carefully insert probe and clamp snugly with screwdriver.

3. Install CHT probes, P/N 40100, in threaded wells on cylinders. Torque probe bodies to 25-30 inch pounds.

4. Install terminals on #20 type J & K thermocouple wire

5. WIRES MUST HAVE A 1/4" DRIP LOOP TO PREVENT OIL OR SOLVENT FROM RUNNING INTO THE

PROBE.

This wire is very hard and will loosen inside a crimped brass or copper terminal, as there is no “cold welding” action like

there is with crimped copper wire.

To prevent loosening of the crimp in service proceed as follows:

1. Strip wire exposing 3/8” of core conductor. Take care not to nick or cut the conductor.

2. Double end of wire back in hairpin bend so crimp is on doubled wire.

3. Crimp on a non-insulated barrel terminal using a crimping tool designed for non-insulated terminals. Be sure

that the barrel seam is facing the rounded side of the crimping tool and not the crimping post as this will result in

a poor crimp.

4. Place a drop of Alpha Metals 51022 liquid soldering flux (Ace Hardware) in open end of crimp and then heat

and sweat in rosin core solder to fill the joint.

2. Fasten the extensions to the engine by means of clamps held by valve cover screws or by tying the extensions to

intake tubes. If the extension goes up to a valve cover, provide some slack for a “drip loop” so that oil and engine

cleaning solvents will drip off probe lead and not run into the end of the probe. It is important that the probe lead or

extension wire be first clamped or tied to the engine before being tied to the engine mount or airframe, to keep

“working” of the probe lead as it comes out of the body to a minimum. AVOID CONTACT OF LEADS WITH

CYLINDER HEADS OR EXHAUST PIPES. USE SLEEVING OVER LEADS IF TYING TO IGNITION HARNESS. If

leads cannot pass through firewall with other wiring, drill a 3/8” hole in firewall and use a neoprene grommet for each

4 to 6 leads, seal with a sealing compound.