Overheat Sensor - TOHATSU 40 Service Manual

OVERHEAT SENSOR

Overheat sensor (1) is a heat sensitive switch installed in the
1
cylinder head to monitor engine temperature The sensor is
connected in series with the warning horn. If the sensor detects
temperature in excess of a predetermined limit, contacts close and
cause the warning horn to emit a continuous tone when the key
switch is ON and the remote control lever is in the FORWARD or
REVERSE position. Depending on model, the engine RPM
limitation function will also activate.
The overheat sensor is not standard equipment on
model 40 prior to 1994 but is available as an option.
Function Test
1. Disconnect the overheat sensor bullet connector at the electrical
box and the ground wire.
2. Remove the overheat sensor from the cylinder head.
3. Using a continuity light or calibrated ohmmeter, connect one
tester lead to each sensor lead.
4. Place sensor and thermometer in a heat-resistant container
2
filled with automotive crankcase oil. Slowly heat the oil using
an external heat source.
Avoid fire or explosion:
• Use a heat-resistant container such as Pyrex
glassware.
• Use oil with a flashpoint above 300˚F [150˚C].
• DO NOT use open flame as a heat source.
5. Verify the sensor switch reacts to the changing temperature as
follows:
Switch Closed
Model (Continuity Present)
40 / 50
60 / 70
80 / 90
115 / 120 / 140
Apply light coat of dielectric lubricant to sensor before
3
installation.
3-/ 4-Cylinder
NOTE
WARNING
Switch Open
(No Continuity)
˚F [˚C]
212 [100]
257 [125]
176 [80]
212 [100]
NOTE
®
˚F [˚C]
185 [85]
230 [110]
156 [69]
185 [85]
POWERHEAD
T1164
T1165
T1248
4-11