EGT Probe Installation and Information
This covers installation of the EGT probe manufactured by J.P. Instruments. While EGT probes manufactured by others also follow identical procedures, please read their manufacturer instructions for specifics.
If your aircraft previously had an EGT installed, the new EGT by J.P. Instruments will fit into the existing holes in the exhaust stack. This applies to any engine having probe holes of 1/8" to 1/4" diameter. If fitting an EGT probe where none existed previously, you will need to drill a 1/8" diameter hole and ream to fit. Before you begin drilling, mark the spots where you will need to drill. Each probe should have a uniform distance separating them from each other and from the exhaust stack flange. A nominal distance of 2 to 4 inches from the exhaust flange is recommended.
Sometimes the mandatory 2 to 4 inch clearance might not be available because of slip joints or bends in the exhaust system or other obstructions. If this is the case then you will have to make do with whatever space is available but just position the probes a uniform distance from the flange.
Before you begin drilling, be certain that nothing will interfere with the EGT probe, or the clamp, the clamp screw or the wires connecting the EGT probe.
After drilling the hole for the probe, insert the Fuel Gauges into the hole so that the tip of the probe is in the centre of the exhaust stream. Tighten the stainless steel clamp to a torque of 45 in/Lbs. Cut off the excess strap close to the screw. Do not mount the probe in a slip-joint of any kind – this will not only void the warranty, the probe will not work as intended.
After the EGT probe has been mounted, Crimp ring terminals with AMP part 45518 crimp tool or its equivalent. Fold back the wire double before crimping terminals. The most common cause of probe problems is poor terminal crimps.
1. Provide sufficient service loops at the EGT Monitors.
2. Thermocouple wire length of the EGT probe is not critical. Trim to required length, allowing for service loops at the engine so that probes can be swapped with probes on adjacent cylinders for troubleshooting purposes.
3. Dress all wires away from high temperature components such as exhaust stacks.
4. Never splice thermocouple wire using copper wire. Use only K-type thermocouple wire. Solder using zinc chloride flux such as Nokorode brand – rosin flux alone won’t work.
5. Observe correct polarity on all probe wires. Connect like colours together (red to red, yellow to yellow).
The EGT kit provided by J.P. Instruments also has a large EGT clamp. This is meant for aircraft with radial engines.
If your aircraft has a radial engine, use the large EGT clamp to fit the 2.5 inch exhaust pipe. The EGT probe should be placed between the accumulator and the exhaust pipe flange and placed at a distance of 2 to 3 inches from the Slimline Instruments flange. Do not route the EGT harness with the ignition harness. Do not extend the yellow thermocouple leads with copper wire.