How It Works; Testing - Toro Diesel Z Master Service Manual

ELECTRICAL

How It Works

A relay is an electrically actuated switch.
1. Coil: Terminals 85 and 86 are connected to a coil.
Applying 12 volts to these terminals energizes the
coil turning it into an electromagnet.
2. Switch: Terminals 30, 87 and 87a are actually part
of a single pole, double throw (SPDT) switch. Term-
inal 30 is the common lead. The switch is spring
loaded so that 30 and 87a are connected when the
coil is not energized. When the coil is energized, the
switch is "thrown" and 30 and 87 are connected (Fig.
648).
6
6-2
Fig 648 CLR DSC-2517

Testing

85
87 87a
86
Fig 649
1. Disconnect the relay from the harness.
2. Verify the coil resistance between terminals 85 and
86 with a multimeter (ohms setting). Resistance
should be from 70 to 90 ohms. There should be
continuity between terminals 87a and 30.
3. Connect multimeter (ohms setting) leads to relay
terminals 30 and 87. Ground terminal 86 and apply
+12 VDC to 85. The relay should make and break
continuity between terminals 30 and 87 when 12
VDC is applied and removed from terminal 85.
4. Connect multimeter (ohms setting) leads to relay
terminals 30 and 87a. Apply +12 VDC to terminal
85. With terminal 86 still grounded, the relay should
break and make continuity between terminals 30
and 87a as 12 VDC is applied and removed from
terminal.
Z580/Z593/Z595 Diesel Service Manual
30
relay pin diagram