fan motor switch honda vt750

I'm consolidating my ignition switch and starter button into one unit (automotive type where you just crank the key).

On the old setup, the ignition switch has three wires. switching the key activates all three:
FAN - power to fan motor (has it's own fuse)
IG - accesories
BAT1 - battery (fused)

The new switch doesn't have a terminal for FAN..which gets power directly from battery. Could I just the tap the BAT1 line?? Would it overload something?
Do I need a relay, and how would I set that up?

I'm new at this. It's a honda shadow aero 2007 vt750. Any ideas?

You should be able to use a relay to supply fan power - ie, the switch supplies #86 (with #85 to GND) & #30 to +12V (via fuse); #86 to fan.

However find out what is controlling your fan.
It may be a relay from a thermister etc in which case may simply need to reconnect that relay's coil feed.
If it's a direct switching (high current) thermal switch, I'd suggest rewiring to have the thermal-switch switch the coil, but that's to take the strain off the thermal switch. (Like brake & reverse etc switches, they'll usually last longer switching a relay rather than 2 or more 21W etc bulbs direct. Only where contact whetting is required might high currents (maybe 0.5 - 1A) be required; but coil spikes usually suffice for that.)

Thanks for the reply.


This diagram is for the ACE. The fan motor circuit is the same.
As you can see, the only wire I need to mess with connects to the old ignition switch.

So I couldn't splice it to the battery or accesory wire?
(the other two wires coming from the ignition switch).

I guess I could do a relay.

No diagram posted.

What I mean is that if your new switch cannot handle the fan power (or anything else for that matter) just use its IGN to supply the +12V to the +ve (86) of a relay coil, then 85 goes to whatever GROUNDING switch (eg, thermostat) is to activate the coil and hence relay contacts 30 & 87. 30 can be fused from battery +12V & 87 to whatever load (eg, fan).
When IGN is off, the relay turn off.

Ok. That makes sense. Still scratching my head on how to make that happen with what I have. I isolated all the wires I thought were relevant in the pictures.

Not sure if the thermostatic switch just turns on the light, or controls the fan switch. Seems like it just lights the bulb correct?

In the fist image IG just sends power to horn, turn and stop (fused. On the new switch this will be ACC. START engages the solenoid when key is turned, getting rid of the starter button.

The Green wire seems to be a main ground for the electronics on the bike (ECM, headlight, meter unit).

....

The new switch does have two terminals for a Magneto as well. Possibility??

The Magneto position is probably closed contacts with the key off.
Add a relay: Terminal 86 to RED / blue at ignition switch, terminal 85 to green or chassis ground. Terminal 30 to red at ignition switch, terminal 87 to blue/orange at ignition switch.
Or you could rewire to have the relay control the fan through the thermo switch. This would keep high current from flowing through the thermo switch.

Ok right. So I could still run the indicator light off the same wire? As in picture:

The 86 terminal of the relay only needs to be connected to the ignition position of the new switch. The fan motor is controlled by the thermo switch. The engine coolant temp sensor, temp indicator control unit, and temp indicator are an independent system.

So as is the 'fan motor switch' trips the fan motor. So I could get rid of the fan motor switch, and ground the motor itself. Then thermo switch to 86; trips fan motor when temp is reached.

Is this what you meant by 'rewiring to have the relay control the fan through the thermostatic switch'?

86 needs to be wired to the switching mechanism, to trip the load (87). right?
That ACE diagram is slightly different than my bike, the ignition position on mine just sends fused power to turn signals, horn and brake lights.
Would look like this??

IMO yes to your verbal, but no the diagram.
Keep the "fan motor switch" to GND 85 of the FAN relay - ie, 86 to IGN, and 30 & 87 in series with the fan - ie, between its + and +12V (battery; fused) for a grounded FAN.

It looks like your fan is "single wire" - ie, its GND is thru case to bike chassis/engine GND - but if the Fan motor "-ve" has a wire INDEPENDENT of (case) GND, it could go thru FAN Relay contacts 30 & 87 to GND.
The latter is how usually done on vehicles since "GND switching" requires less wire (no wire to +12V, instead a wire to a nearby chassis GND) and that parallel relays or switches for alternate fan-on commands/sensors are simply paralleled whereas the +12V switch's equivalent requires diodes to prevent power backfeed to other +12V sources IF they are different (eg, battery, IGN, ACC, ECU +12V, etc). Also no lengthy +12V cable to short to chassis.

The FAN MOTOR SWITCH (sensor with switching to handle fan current) has a lower setting than the "TEMP LIGHT" switch which (probably) is a mere warning of impeding engine damage or that their may be a FAN or coolant problem etc.
If the "TEMP LIGHT" merely indicated "I'm hot and the fan is on", it would switched by the FAN circuit.
A relay (86) from the TEMP LIGHT with 30 & 87 connected in parallel to FAN RELAY's 30 & 87 will switch on the FAN in case of FAN MOTOR SWITCH or FAN RELAY failure. (If it's a relay fault you interchange the 86 & 85 between the relays (ie, FAN MOTOR SWITCH relay and TEMP LIGHT relay) to resume normal operation.
Using the temp warning to turn on the fan is a great backup, but it's not good long term for the engine, but it's still way better than the engine blowing if you the light wasn't working, or if you ignore etc... [KIDDIES - please learn to check initial IGN-on warning light tests, and do NOT ignore them if they light later...   {I recall the driver that ignored the little red "O" light. The next 2 minutes cost them >$1000... the engine seized. d'Oh!}]

Adding an extra temp sensor - maybe a $5 Klixon temperature switch - means sensor redundancy.