Mercury MerCruiser MCM 454 Mag MPI Service Manual page 408

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SERVICE MANUAL NUMBER 23

1. Connect one lead of an ohmmeter to one terminal of transmission switch. Connect the

2. Switch should read no continuity. If continuity exists, replace the switch.

The following test involves the use of intense heat. Failure to follow appropriate

procedures or warnings can cause burns which can result in severe personal injury.

While performing the following test, observe these general precautions:

Use only clean, dry sand such as used for general sandblasting purposes. Use of

sand containing contaminants could result in hazards such as fire, short circuiting,

hot-spots, or other hazards.

3. With an ohmmeter connected as outlined and using suitable container, thermometer

90-861326--1 MARCH 1999

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other lead of ohmmeter to other terminal.

Ohmmeter Leads

Transmission Fluid Temperature Switch

Wear personal protective clothing such as rubber gloves, a non-flammable

apron, and eye protection - preferably full face shield or safety glasses.

The appropriate heat source should only be electric. Heat source should be

operated by a qualified person. Be sure to follow all instructions of the

manufacturer of the heat source. The heat source should be checked each time

it is used to be sure it is functioning properly.

The thermometer used in the test should be a high-temperature thermometer

with a maximum reading of at least 300 F (150 C). Under no circumstances

should the operator allow temperatures to exceed test specifications.

Perform test only in a well ventilated area.

Use a suitable container, such as metal, to hold the sand. Avoid use of glass

containers unless the operator first confirms for himself/herself that the glass

container is an appropriate high-temperature vessel.

Because the components will reach high temperatures DO NOT handle

materials or components until COMPLETELY cooled.

and heat source, suspend sender with tip in sand.

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