article was written to try to assist someone who had an intermittent
problem with their cooling fan. The fan would operate sometimes
and not others depending (apparently) on the bike hitting a bump.
you don't have a wiring diagram, download a copy from Mark's
site. Wiring Diagram.
If you print the diagram (maybe blow up the section you need),
you will be able to use a marker to trace over the wires as
you check to avoid being confused.
to be annoyed, frustrated and confused but not necessarily in
that order. Electrical is the weakest area in most technicians
practice but shouldn't be because it is simply a matter of deduction
(or maybe that should be induction! VBG) Time, experience and
practice will see your skills improve. There is nothing magic
relay circuit has two main parts, the part that controls the
relay and the part that is controlled by the relay. A relay
is simply a switch that is operated electrically. Allowing power
to flow to the electro-magnet winding will create a magnetic
field that attracts the contact arm. This is the "click"
you hear when a relay operates- the relay contacts snapping
together. When operating a switch, you perform the action that
is done by the control circuit in a relay.
typical Bosch type relay has 5 connections as follows:
& 2- Winding (control circuit) has two connections, one
for each "end" of the winding.
Contact arm (common in the switched or controlled circuit.)
Normally open contact.
Normally closed contact.
relays share two connections to one connector as in a ground
for the control winding connected along with the normally closed
relay's controlled or switched circuit has the movable contact
arm that is held away from the normally open contact by spring
pressure. This "normally open" contact is simply that,
normally open, not connected. When the relay has power applied
to the magnet, "click" the contact arm's contact snaps
against the normally open contact and power can flow through
the circuit just like would happen if you touched two wires
together or flipped a switch.
relays have a normally closed contact also as I said earlier
and the contact arm is in contact with the normally closed contact
unless power is applied to the relay's winding. This normally
closed circuit is useful to have something turned on when power
isn't flowing in a circuit such as operating low beams then
using a switch to close the relay to operate high beam. If the
switch fails the circuit will fail with the low beams on so
some lights will be always available.
the wiring diagram will allow you to determine the wires that
form the control and controlled (switched) circuits to the relay.
Once you know which wire is which, you can use a test light
or voltmeter to see whether power is available to the switched
circuit (relay connector with one lead of your test light and
ground with the other). You can easily make a test light for
doing this with a small light bulb and socket. A pair of spade
lug connectors on the ends of the bulb socket wires will allow
you to plug into the relay plug connections for hands free.
should have power to one of the control circuit connections
(per the wiring diagram) and the other connection should be
connected to the bike's frame (ground circuit) when the radiator
is hot enough to close the temperature switch. The ground circuit
connects back to the battery negative to complete the path for
power to the battery.
bet is that you have either, a broken wire making and breaking
connection inside the insulation or a loose ground connection.
test for power to the control circuit connection on the relay
connector, remember that this circuit is hot all the time so
you shouldn't have to have the key on. In order to check the
ground connection on the relay plug, you will have to remove
the plug from the temperature switch in the bottom of the radiator
and connect the wire to a good ground ( a bare metal part such
as a bolt).
you plug a test light into the two control circuit connections
in the relay plug, the light should come on whenever the temperature
switch wire is touched to ground and go off when the switch
wire is removed from ground.
test the controlled (switched) half of the circuit, the first
test might be to connect a wire between the two connections
for this circuit on the relay plug (per the wiring diagram).
The fan should operate whenever these two connectors are bridged
with a wire.
the fan operates with the controlled (switched) connectors bridged,
wiggle, prod and push all the wires you can reach to see if
the fan operates or stops (depending). If it does you will have
to fiddle with the wiring to try to localize the intermittent
connection. If it doesn't operate, try wiggling the wires to
see if it operates as you will be trying to make the bad connection
open and close the circuit in order to figure out where the
problem lies in the harness.
this does not show up the fault, try the same thing by connecting
your test light across the control circuit connections in the
relay plug, then push prod and wiggle.
option, if you can't locate the broken wire or bad connection
is to determine whether the power wire or fan wire (load wire)
is the one that is at fault. This will be useful if the wires
are run together where the fault lies since wiggling the wires
will not allow you to blame one wire in particular.
order to see which wire is at fault, first connect your test
light from the powered connector (the one which comes from the
battery positive through the fuse), to a good ground and do
the wiggle bit. If the light will come on or off then this wire
is at fault (or you haven't succeeded in operating the bad connection).
this doesn't show the fault, connect your test light from the
battery positive to the switched contact of the relay connector
plug (the one to the fan). The fan will not run because the
test light has too much resistance to allow enough current flow
to run the fan. On the other hand, the fan will allow ample
current flow for the test light to operate so it should light.
Now wiggle the wires to see if the test light flickers, goes
off or comes on to locate the fault.
if the fault could not be localized to one wire in particular
on the control side of the circuit, you can test the wires individually
by connecting your test light from the battery positive to the
relay plug connection which goes to the temperature switch,
ground the switch connector and proceed to wiggle, prod and
push. The other wire can be tested by connecting your test light
between the control circuit's powered wire and ground, wiggle.
you can't locate the fault by this method then you may wish
to simply rewire the fan circuit.