Mercury 25 EFI Service Manual page 374

Power Trim
Power Trim Relay Test Procedure
The trim motor relay system used on permanent magnet trim systems connect each of the two wires from the trim motor to
either ground or positive in order to allow the motor to run in both directions.
If the motor will not run in the up direction, it may be either the up relay is not making contact to 12 volts, or the down relay is
not making contact to ground. The opposite is true if the system will not run down. When the system is not energized, both
relays should connect the heavy motor leads to ground.
To test which relay is faulty if the trim system does not operate in one direction:
1. Disconnect the heavy gauge pump wires from the trim control relay.
2. Check for continuity between each relay terminal and ground.
DMT 2004 Digital Multimeter
Red
Green relay terminal
Blue relay terminal
3. Replace the relay that does not have continuity.
4. Connect a voltmeter to the blue relay terminal and to ground. There should be 12 volts on the blue lead when the up switch
is pushed.
5. Connect a voltmeter to the green relay terminal and to ground. There should be 12 volts on the green lead when the down
switch is pushed.
Red
Green relay terminal
Blue relay terminal
6. Replace the relay that does not switch the lead to positive.
7. Reconnect the heavy gauge pump wires to the trim control relay.
Page 5B-12
a
Meter Test Leads
Black
Ground
Ground
Meter Test Leads
Black
Ground
Ground
© 2016 Mercury Marine
b
a -
b -
20926
91‑892647A01
Meter Scale
Full continuity (R x 1)
Full continuity (R x 1)
Meter Scale
Voltage ‑ DC
Voltage ‑ DC
Green heavy gauge pump wire/green
relay terminal (down)
Blue heavy gauge pump wire/blue relay
terminal (up)
Reading (Ω)
< 20 Ω
< 20 Ω
Reading (Ω)
Battery voltage (12V)
Battery voltage (12V)
90-8M0105568 eng MARCH 2016