Piper Arrow IV, Maintenance Manual

Page: 660 / 752

EXHAUST GAS TEMPERATURE GAUGE. (Alcor)
This instrument, which is commonly referred to as EGT, is used to aid the pilot in selecting the economical
fuel-air mixture for cruising flight at a power setting of 75% or less. It is a sensing device to monitor the fuel
air mixture leaving the engine cylinders. This gauge is adjustable. If it is found defective after checking with
troubleshooting chart it should be replaced. If the leads to the gauge are defective in any way they should be
replaced. When replacing leads, it is very important to use the same type and length of wire as the resistance of
the leads is critical for the proper operation of this gauge.
REMOVAL OF EGT PROBE AND GAUGE.
1. Disconnect wires from the EGT gauge at the instrument panel.
2. Remove four bolts which secure the gauge to the instrument panel and remove the gauge.
3. Remove wires from the wire harness going to the engine.
4. Loosen the clamp which secures the EGT probe to the number two cylinder exhaust manifold and
remove the probe.
CLEANING AND INSPECTION OF EGT.
Unless mechanical damage is evident, broken glass, bent or broken pointer, or broken case, the following
checks should be performed before removing the instrument:
1. Remove the probe from the exhaust stack and check for a broken weld (at tip end) or a burnt off end.
The measured resistance of probe should be .8 ohms. Clean the connections with steel wool before reassembly.
2. Disconnect the lead wires at the instrument and measure. Resistance with the lead wires connected to
probe should be 3.3 ohms. Clean connections with steel wool before reassembly.
3. With the leads connected to instrument, heat probe with propane torch to dull red. The meter should
read up to the fourth graduation or approximately 1500° F. Before making this check, make sure that the
adjustment screw, located at the rear of the instrument case, is in the center of its travel. If this screw has been
turned to either end of full travel, it will shut the instrument off and no indication will be shown on the pointer.
If meter still does not read, replace it.
—CAUTION—
Do not connect ohmmeter across meter. It will burn out the
movement of the meter.
INSTALLATION OF EGT PROBE AND GAUGE.
1. Install the probe into the hole in the number two cylinder exhaust manifold and secure with clamp.
2. Route the thermocouple wires along with the existing wire harness to the instrument panel.
3. Install the EGT gauge into the instrument panel and secure with four bolts.
4. Connect the thermocouple wires to the rear of the EGT gauge.
77-20-05
Page 77-04
December 1, 1978
3F21
PIPER AIRCRAFT
PA-28RT-201 / 201T
MAINTENANCE MANUAL