Aetna SM Versions - Manual (Page 3)

Testing;
Reconnect the battery and turn the ignition on.
The display should illuminate and show "0000"
indicating power is reaching the unit. Start the
engine and verify that the display indicates
engine RPM, When the engine is cold and idling
without load the right hand digits may seem to
"jump." This is due to fluctuation in the engine
speed and is pronounced because the readout
displays variations as small as one RPM. The
RPM's should steady when the engine is warmed
and operated above idle under a constant load.
Should the display continue to jump excessively
check engine tuning, look for a fouled injector or
a fuel suction line air leak. Contact the factory
for more suggestions.
K
If the tachometer shows all zeros with the engine
running, check the signal wiring from the engine.
If the tachometers digits fail to show at all, the
problem is in the power wiring to the tachometer
and not in the signal wiring. If the indicated
RPM is in error, check that the ratio select
switches are set properly.
The tachometer includes special circuitry to
minimize loran interference from the digital
processor. Nevertheless, if a loran set is
aboard, it should be checked for interference by
observing the loran SNR when the ignition is on
without the engine running. Be sure any
interference isn't from an alarm buzzer or bell. If
interference is detected, check the loran antenna
& ground or install a filter, such as the "MAR-P5"
from Marine Technology (562) 595-6521, in the
+12 voit power and ground leads to the
tachometer.
The tachometer is now ready to use. No
adjustment is ever necessary. The circuitry
employs a piezoelectric crystal to permanently
maintain calibration.
On the Mode! 8402 the built-in dimmer senses
the ambient light and adjusts the display
intensity for comfortable viewing. When
operated in bright light the case will feel vrarm to
the touch. This is normal and will not damage
the unit provided the case temperature does not
exceed 175 degrees.
The Model 8905 has internal backlighting
provided by solid state lamps that do not require
routine replacement, The 8905 consumes less
than one-half watt and does not create
significant heat.
A special anti-fogging compound is applied to
the inside of the glass during manufacture.
Internal fogging of the glass may be reduced by
removing the ratio switch cap. In cases of
persistent fogging, contact the factory for
additional help. No routine maintenance of the
tachometer is required. Clean the glass with a
soft cloth. The sensor end of the sender should
be cleaned periodically of any accumulation of
magnetic particles which can shunt the magnetic
sensitivity.
The sender may be tested with an ohmmeter.
Measurement of the resistance on the leads
should be between 100 and 1000 ohms. During
installation, wiring can be verified by temporarily
running a separate wire pair directly from the
sender to the tachometer.
Limited Warranty
Aetna Engineering warrants its tachometers to
be free of defects in material and workmanship
for a period of two years from the date of
purchase as shown on the original consumers
purchase receipt.
Warranty service will be provided free of charge
if the unit is delivered to Aetna Engineering
during the warranty period accompanied by
original consumer proof of purchase. Any
transportation, removal, or reinstallation charges
will be paid by the purchaser whenever incurred
in connection with this warranty. In absence of
proof of purchase receipt, the warranty period
shall be two years from the date of manufacture.
This warranty does not apply to units subjected
to misuse, neglect, accident, incorrect
installation wiring, improper installation, water
damage, or units used in violation of the
installation instructions furnished by us. This
warranty excludes any incidental or
consequential damages connected with failure or
defect in the product. Aetna Engineering
products are not designed, intended or approved
for use on or involving aircraft or in hazardous
locations.
This warranty gives you specific legal rights and
you may have other rights which vary from state
to state.