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Function
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Typical terminal designation
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Operation
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Normally Open 4 pin relay
12v 20A 4 pin relay
12v 30A relay with detachable bracket 12v 30A relay with inc blade
fuse
12v 40A relay NO 4 pin
12v 70A heavy duty 4 pin relay
24v 20A
4 pin NO relay
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30 Supply Input
87 Supply Output
85 Coil ground or -ve
86 Coil trigger
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A control circuit between pins 85 & 86 eg, with light duty control switch and wiring , may be used to switch a second
circuit with heavier current load via wiring between pins 30 and 87
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30 Supply Input
87 Supply Output
85 Coil ground or -ve
86 Coil trigger
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Normally open relay often
used on construction plant for starter
circuit control
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Double Make & Break
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30 Supply Input
87 Supply Output(1)
87b Supply Output(2)
85 Coil ground or -ve
86 Coil trigger
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Similar operation to the standard 4 pin Normally Open relay but has a second terminal in parallel to the output terminal.
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Changeover Relay 5 pin
12v 20A/30A relay
12v 30A/40A relay
24v 10A/20A automotive relay
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30 Supply Input
87 Supply Output when relay off.
87a Supply Output when relay on.
85 Coil ground or negative.
86 Coil trigger or positive
from switch.
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A control circuit
wired to pins 85 & 86 eg, with light duty control switch and wiring , may be used to
relay switching of a second
circuit with heavier current wired to pins 30 and 87
when control circuit is OFF , changing to pins 30 and 87a
when
control circuit is ON
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Flasher Relay
SAFU003 direction
indicator relay SAFU005 flasher relay
4 pin with C terminal for trailer lights
warning lamp
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31 Ground or Negative
49 Supply Input battery +ve
49a Supply output to column switch then to indicator lamps.
49b Second output to direction indicator lamps
49c Third output to direction
indicator lamps
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The flasher relay or direction indicator
relay pulses power to indicator lamps causing to flash on and off at between 60 and 120 flashes per minute in normal operation.
Always check pin position configuration of
relay is correct before fitting
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Fuel Pump Relay
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1 Ignition Coil (negative pulse)
15 Ignition supply from ignition switch
31 Ground or negative
50 Starter motor cranking signal
85 ground for coil may be switched via engine computer.
30 Battery +ve Supply
87 +ve Supply output to fuel pump.
Wiring terminal designation may be vehicle specific, consult manufacturers specification.
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The fuel pump relay may supply power to the fuel pump for a couple of seconds to prime fuel system then shuts off until control circuit via engine
control computer grounds coil of relay to switch on again if engine rotation signal is present
from crankshaft position sensor or
distributor pickup.
Fuel pump relays are vehicle specific in application.
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Glow plug controller relay
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(L) dashboard preheat warning lamp
(85) or (31) coil negative
(86) or (15) from ignition switch , coil trigger +ve.
(30) Battery B+ +ve supply
(87) +ve output to energise pre heat plugs (glow plugs)
Wiring terminal designation may be vehicle specific, consult manufacturers specification.
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The
glow plug controller is typically a timer relay which allows diesel glow plugs to heat up for approx 10 seconds to provide pre heating of
air in the engine pre combustion chambers to allow easier cold starting. May also have post heat functions.
Operation may also be controlled by engine control unit on later vehicles.
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Time delay relay
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Wiring terminal designation may be vehicle specific, consult manufacturers specification.
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Time
delay relays may be used for such
applications as wash wipe interval, heated
rear window, time delayed motor
operation, bus door operation.
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