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I'm designing a small relay panel for my CB750 and want to keep it as simple as possible. I've always done separate relays for high and low beam but i'm wondering if there is a way to accomplish this with a single relay somehow that i'm not thinking of.
I want a relay for the ignition, one for accessories and was hoping to just add in 1 relay for both high and low beam
Thanks for taking the time, but I must admit I am not following you.
When you say N/O and N/C contacts, are you talking about pins 87 and 87a on the relay? .... because if so, I'm not seeing how you can avoid the low beam (via N/C (87a)) staying on all the time.
I guess I'm not really sure what you mean by driving the power to the relay coil through the high beam switch but then also saying to power the coil through the NC NO contacts for high beam and low beam
Could you draw up a diagram on a piece of paper and upload the pic?
If you want to run with headlight always on with the key its pretty simple.
Just run a SPDT relay and put the lows on the NC circuit and the highs on the NO circuit.
So highs to 87 and lows to 87a.
When the relay is not energized you have a low beam, when you flip the high beam switch (energize the relay) you have high beams.
If you want to run with headlight always on with the key its pretty simple.
Just run a SPDT relay and put the lows on the NC circuit and the highs on the NO circuit.
So highs to 87 and lows to 87a.
When the relay is not energized you have a low beam, when you flip the high beam switch (energize the relay) you have high beams.
This is the best way, and not using the relay coil except for when needing high beam, which should be very seldom overall. Simple and effective, just make sure the relay contacts can handle the load (even better with LEDs).
But the 87a pin is connected to pin 30 when relay coil is not energized ....which means my low beam would be ON even when everything on the bike is shut down!
I'm not sure how you guys get 87a to NOT stay on all the time. I have never seen that done before.
I will take a look as soon as I'm out by the bike today ... it is a 83 honda cb750sc - nighthawk.
The relay I was hoping to use is just the standard Bosch style with pins 85, 86, 87 and 30 (+ 87a)
As mentioned the 87a pin has, in my experience, always stayed on, so not sure how some are getting that to work as it's by default connected to pin 30 when relay is not energized
On second thought ... I plan on having an aux relay as well so I guess I could use that relay (switched on with key) to power the lights relay and not have the lights relay directly connected to the battery, which would solve the 87a on-all-the-time issue.
The relays are all 30-40amp these days so with the right size wires should be no problem wiring the lights on top of aux (heated grips and phone charger)
A single relay will work if you connect pin 30 to a switched power source.
For instance, the black wires in your harness will have power only when the ignition switch is turned on and so pin 30 can connect here. Then 87a (which is on all the time) is for your low beam and 87 is for your high beam.
Honda shuts the headlight off when the start button is pressed so headlights not sucking an extra 1.21 Jiggawatts while picking solenoid, powering starter motor and ignition coils.
Its just easier on the whole system.
A single relay will work if you connect pin 30 to a switched power source.
For instance, the black wires in your harness will have power only when the ignition switch is turned on and so pin 30 can connect here. Then 87a (which is on all the time) is for your low beam and 87 is for your high beam.
Depending on the make/model/year, many of the black wires (especially those coming directly from the ignition switch) will be 14 gauge. Just fine, I figure.
It's kinda normal to run headlight through relay if you fit higher wattage bulbs or even to make sure you get full battery voltage to headlight. (particularly if your doing a lot of nighttime riding, did my 550 in 1978)
chickenStripCharlie said:
But the 87a pin is connected to pin 30 when relay coil is not energized ....which means my low beam would be ON even when everything on the bike is shut down!
I'm not sure how you guys get 87a to NOT stay on all the time. I have never seen that done before.
You need a second relay to control the first one. I didn't bother and just cut the ground wire to headlight then ran it through a normal on/off switch. You can get better charging by running battery direct to field coil through a relay. Output to headlight at same point.
trek97 said:
Sheesh. ;D
Honda shuts the headlight off when the start button is pressed so headlights not sucking an extra 1.21 Jiggawatts while picking solenoid, powering starter motor and ignition coils.
Its just easier on the whole system.
When did they start doing that? I've never seen it on any 1970's bikes and Kawasaki were the only people doing it in the early 80's? (through to at least 2005 when everyone else caught up)
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