PIPER AIRCRAFT, INC.
PA-28-161, WARRIOR III
MAINTENANCE MANUAL
PAGE 1
Nov 30/06
4J21
71-60-00
AIR INTAKES
1. Carburetor Ice Detector (See Figure 1.)
A. Description
The optional carburetor ice detection system is an advisory system only and is designed to alert the
pilot to impending engine power loss or stoppage due to ice/frost accumulation inside the
carburetor. The pilot should apply carburetor heat in response to this warning. Unlike temperature
sensing devices, the carburetor ice detection system utilizes an electronic light source and feedback
sensor (i.e. - optical probe). A red warning light inside the cockpit is activated when the probe’s
radiated light beam and photo-detector sensor, located in the carburetor throat, is blocked due to
ice/frost formation. In the absence of carburetor ice/frost the red warning light automatically
deactivates.
A rotary sensitivity adjustment control knob is provided to adjust the system sensitivity level for
ice/frost detection. This setting should be just above the threshold where the red warning light
deactivates and should be set after engine start.
B. Functional Check
(1) Aircraft master switch ON.
(2) Ice detector switch ON.
(3) Adjust sensitivity knob until RED light (ice light) goes OUT. This is a critical setting.
(4) Turn ice detection system OFF, then ON. Red light must flash ON, then OFF, indicating all
components are operating normally.
C. Normal Maintenance
(1) With increasing time of operation on the engine a slight film of fuel residue may form on the
probe, which may result in a slight reduction of sensitivity as compared to the original setting
when the ice detector is first installed. This will be observed when it is required to turn the
sensitivity adjustment knob to an ever increasing clockwise or higher setting as time goes on.
However, the basic ice detection sensitivity is not reduced when adjusted as prescribed herein.
(2) In the event the sensitivity adjustment control must be turned to the full clockwise position and
the red warning light does not deactivate, then the probe must be removed and cleaned with a
soft cloth (preferably a cotton swab) and white gasoline. Exercise caution not to bend or move
the probe's photo-detecting sensing component. Once cleaned, reinstall the probe assembly
and check out the system using the instructions prescribed in this manual.
D. Ice Detector Probe
(1) Removal
(a) Remove engine cowling.
(b) Probe is mounted in carburetor upstream of the throttle valve control arm. Remove safety
wire and carefully unscrew probe from carburetor. Measure and note how far probe
extends into carburetor. Note number of shims used.
(c) Where wires for probe come off engine mount, remove wire insulation sleeves; note the
respective wire interconnects and disconnect wires.
(d) If engine is to be operated, install a suitable plug.
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