Author Topic: Lets Talk Headlight Relays  (Read 1386 times)

Offline Kiwi_Roy

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Lets Talk Headlight Relays
« on: August 16, 2020, 05:12:37 PM »
All modern Guzzi's have headlight relays aka Light Logic Relay
These relays may be fed from a fuse or sometimes they are fed directly by the alternator.

One weak link in the wiring is the tiny wires to and from the dimmer switch on the left handlebar.
One way you can improve an incandescent headlight is to bypass the dimmer switch adding a relay inside the headlight bucket to do the switching thus saving significant Voltage drop.
Voltage drop is not so significant for an LED headlight since they deliberately drop Voltage at the bulb, if you read the specs on a typical JED it calls for 9 - 32 Volts which means they only need 9 Volts for full output where as with an incandescent lamp
the brightness is a function of Voltage to the power of 5 so even half a Volt is really significant once its turned into light.
Auxhillary lamps.
If you look at my typical sketch you will see the feed as far as the dimmer switch wiring is very robust, a typical relay contact would br capable of carrying 30 Amps 24 / 7
A typical headlight bulb rated 60 Watts would draw 5 Amps, easy peasy for any automotive relay
I have shown just one new form C relay One normally open, one normally closed contact.
« Last Edit: August 16, 2020, 11:21:34 PM by Kiwi_Roy »
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Offline Kiwi_Roy

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Re: Lets Talk Headlight Relays
« Reply #1 on: August 16, 2020, 05:41:12 PM »
The existing Guzzi Light Logic relay is fed by a significant fuse, the relay output can easily supply additional lights however its a good idea to fuse them separately in case the wiring shorts out.
The fuse for the additional load should be several sizes smaller so that it can protect the load without blowing the main light fuse.
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Offline John Warner

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Lets Talk Headlight Relays
« Reply #2 on: August 16, 2020, 05:41:45 PM »
Nice write-up, as usual Roy.
I added Relays for mine early on, never a good idea to put that sort of current through a Handlebar Switch.

P.S. You said 'Relay' at one point, instead of 'Bulb' . . .  :tongue:
Quote
A typical headlight relay rated 60 Watts . . .
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Offline mechanicsavant

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Re: Lets Talk Headlight Relays
« Reply #3 on: August 16, 2020, 06:24:47 PM »
I installed a relay on my V7II along w/a slightly higher output bulb .It made a significant difference in light output , still the (imho) poor pattern from the reflector , but brighter . I used a standard 5 pin Bosch relay & a dedicated ground & fused Batt. Power supply . Iíve done this a number of bikes Iíve owned with good results & so far no down side . For those of us who are wiring challenged I think a kit is still available for most headlight types from ďeastern beaverĒ . I have no connections w/them & like me if your significant other sees ďEastern BeaverĒ in your search history please show her itís electrical ! Not a porn site , may i come off the couch now? Dear!

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Re: Lets Talk Headlight Relays
« Reply #3 on: August 16, 2020, 06:24:47 PM »

Offline Testarossa

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Re: Lets Talk Headlight Relays
« Reply #4 on: August 16, 2020, 06:59:52 PM »
Decades ago I installed Bosch relays to take the amps load off the original frail switchgear on the T. Still using that system despite upgrading the switches and using an led headlamp. I put the eastern beaver system on the Mille just because it's more compact -- fits in the shell. Both circuits work well and the quality relays last forever.
« Last Edit: August 16, 2020, 08:02:51 PM by Testarossa »
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Offline Kiwi_Roy

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Re: Lets Talk Headlight Relays
« Reply #5 on: August 16, 2020, 07:45:36 PM »
I installed a relay on my V7II along w/a slightly higher output bulb .It made a significant difference in light output , still the (imho) poor pattern from the reflector , but brighter . I used a standard 5 pin Bosch relay & a dedicated ground & fused Batt. Power supply . Iíve done this a number of bikes Iíve owned with good results & so far no down side . For those of us who are wiring challenged I think a kit is still available for most headlight types from ďeastern beaverĒ . I have no connections w/them & like me if your significant other sees ďEastern BeaverĒ in your search history please show her itís electrical ! Not a porn site , may i come off the couch now? Dear!
While not trying to talk you out of a separate feed I just want to point out the existing relay has a pretty solid feed
http://www.thisoldtractor.com/guzzi007/schematics/2013_V7_Series.gif  15 Amp fuse B in this case.
« Last Edit: August 16, 2020, 07:48:43 PM by Kiwi_Roy »
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Moto Guzzi - making electricians out of riders since March 15 1921

Bert Remington

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Re: Lets Talk Headlight Relays
« Reply #6 on: August 16, 2020, 09:20:38 PM »
Another masterful analysis and explanation KR.  Excellent highlighting of a critical LED feature: operating voltage.

So we are back to the summary advice I gave Caffeino:  LED auxiliary lights with LED H4 headlight on a modern MG don't need a relay but should be fused.  Otherwise use a relay with fuse.

From there we move to the higher level functions offered by Skene Lights which twowheeladdict uses: https://www.skenelights.com/

The Skene Lights website is confusing in the presentation of options.  There are basically three functions on offer:

* Photon Blaster for the front with special conspicuity flicker LED modules (will also flicker LED turn signals)

* P3 for the rear with special conspicuity flicker LED modules  (will also flicker LED turn signals)

* Light dimmers/controller for your headlight and auxiliary lights

I'm quite impressed with their offerings.  Not Guzzi prices but certainly you seem to get what you pay for.  I might be changing my mind on using the Timer Shop programmable relays.  And Rigid fog lights for "conspicuity."

WRT wire connections, KoF recommended soldering which I agree with.  And the use of adhesive (self-sealing) heat shrink tubing.  Magical!

Offline dxhall

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Re: Lets Talk Headlight Relays
« Reply #7 on: August 17, 2020, 08:15:31 AM »
Youíve got me thinking that I should put a few relays in my Eldovert, which I am presently wiring from scratch.  Where do I get the thing (donít know proper term) that the relays plug into?  It would be analogous to a fuse block.

Bert Remington

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Re: Lets Talk Headlight Relays
« Reply #8 on: August 17, 2020, 10:18:05 AM »
If you only need three relays and three fuses with superior weather protection, I recommend this https://www.amazon.com/Concours-Specialties-Waterproof-Marine-Relays/dp/B01FWILO0Y/ref=sr_1_2?dchild=1&keywords=HWB18&qid=1595887078&sr=8-2  You will need a terminal crimping tool that costs about $20.   

They have a larger one but you have to provide relays and fuses: https://www.amazon.com/Waterproof-Fuse-Relay-Block-Panel/dp/B01FWILNCS/ref=sr_1_4?dchild=1&keywords=HWB60&qid=1597676581&sr=8-4

They use the ISO 280 form factor standard so you can buy relays and fuses at Autozone, et al.

If you only need one IGNITION-ON relay, I'm partial to the Fuzeblocks FZ-1.

If you need programmable relay functions, I'm partial to https://www.amazon.com/Small-Timer-Delay-Relay-Cycling/dp/B07C4ZP23D/ref=sr_1_1?dchild=1&keywords=timer.shop&qid=1597677186&sr=8-1.  There are 5amp and 10amp versions from XDP, et al.

Solder, adhesive heat shrink, a DVOM and most important a pre-planned wiring diagram (KR sets the bar) are your friends.  Wiring is usually fun unless it's really old with cracked insulation and corroded terminals.  Best wishes. :smiley:


Offline dxhall

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Re: Lets Talk Headlight Relays
« Reply #9 on: August 17, 2020, 11:36:43 AM »
Thatís a big help.  I know this is a dumb question, but - how do you decide whether a particular circuit needs a relay?  Is it based on the wire gage and amp draw?

Bert Remington

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Re: Lets Talk Headlight Relays
« Reply #10 on: August 17, 2020, 12:06:01 PM »
You sure know how to ask the hard questions. :laugh: As we bureaucrats always say, it depends.

If you are trying to move heavy loads (eg, incandescent headlight) from old switches (I assume an Eldovert is old) then a relay with fused battery feed is good.

If you are adding heavy loads (eg, heated grips or vest) then a relay with fused battery feed is necessary.

If you are changing to trick handlebar switches for looks or function, then a relay with a fused battery feed is best.

If you are adding light loads (eg, GPS navigator, action camera) then a fused battery feed is adequate.

For the ISO 280 relays, the small 20amp size should be adequate.  For wires, #14 AWG is more than adequate for the battery feed to multiple relays.  After that #18 AWG should be adequate.

So what's your next hard question?

Offline Caffeineo

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Re: Lets Talk Headlight Relays
« Reply #11 on: August 17, 2020, 12:13:24 PM »
Kiwi Roy Thank you so much for posting this.  :bow: Electrical stuff is challenging for me because it looks the same if it is working or not. Your diagram is so much easier to understand than the actual wiring diagram I have a much better idea of how the headlight wiring works. Had no idea the ECU would power up the headlight. I just thought it was for the ignition and FI stuff.
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Offline Kiwi_Roy

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Re: Lets Talk Headlight Relays
« Reply #12 on: August 17, 2020, 08:52:25 PM »
Sometimes the relay coil is wired to the dash but its still the ECU that decides to turn the dash output on via the Canbus connection
My V7 turns the headlight on if you push it forward even if the engine is not running the speed sensor and the relay are both wired into the dash but i'm fairly confident in saying the ECU makes the decision.
Unfortunately  Piaggio don't share the logic with us or we could be a lot more helpful.
« Last Edit: August 28, 2020, 06:28:06 AM by Kiwi_Roy »
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Offline Cdn850T5NT

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Re: Lets Talk Headlight Relays
« Reply #13 on: August 17, 2020, 08:56:38 PM »
Nice write-up, as usual Roy.
I added Relays for mine early on, never a good idea to put that sort of current through a Handlebar Switch.

P.S. You said 'Relay' at one point, instead of 'Bulb' . . .  :tongue:

++1
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Offline Kiwi_Roy

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Re: Lets Talk Headlight Relays
« Reply #14 on: August 17, 2020, 09:27:45 PM »
Thatís a big help.  I know this is a dumb question, but - how do you decide whether a particular circuit needs a relay?  Is it based on the wire gage and amp draw?
I usually decide based on the device used to trigger the circuit on, I use a lot of low current devices as switches for example reed switches that are usually rated at a fraction of an amp
A reed switch would weld itself shut if you tried to switch a headlight for example but a relay can take a circuit that's only 0.1 Amp and switch 10 Amps.

A starter solenoid draws up to 40 Amps, if you tried to put that much current through a bar switch it would soon burn out so its run through a relay that can safely switch 60 Amps
I always use a relay on my Horn circuit, thats another circuit that benefits from a high current circuit, they are much louder with a relay.
You will notice that the ECU uses a relay to switch power to the fuel pump, coils and injectors.
A relay will protect fragile circuits like the ECU it isolates the electronic wiring from the high current wiring. Relays are used to separate a low Voltage circuit from High Voltage or high current circuit.
« Last Edit: August 28, 2020, 06:59:58 AM by Kiwi_Roy »
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Offline dxhall

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Re: Lets Talk Headlight Relays
« Reply #15 on: August 17, 2020, 10:02:37 PM »
That makes sense, Roy.  Right now Iím running the run/stop rocker switch on the handlebar directly to the coil circuit.  Would you put a relay in this circuit?  The wires from the handlebar switch are pretty small.

Offline Kiwi_Roy

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Re: Lets Talk Headlight Relays
« Reply #16 on: August 18, 2020, 12:12:37 AM »
That makes sense, Roy.  Right now Iím running the run/stop rocker switch on the handlebar directly to the coil circuit.  Would you put a relay in this circuit?  The wires from the handlebar switch are pretty small.
You are probably ok to power the ignition coil direct, if in doubt scan through Carl Allisons drawings, you will find something similar to the bike you have.
Keep the contacts clean and apply some fresh Vaseline to the contacts every few years.
http://www.thisoldtractor.com/guzzi007/sportissimo.html
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Offline John Warner

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Lets Talk Headlight Relays
« Reply #17 on: August 24, 2020, 11:59:38 PM »
CANBUS?
Didn't think any Guzzis had that, other than maybe the V85?

Quick question.
A couple of the Relays on the Stelvio have a Diode in them, to protect the ECU.
What's the criteria for using that type when adding Relays for other Circuits, if there is one?
Doc out . . .
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Offline Kiwi_Roy

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Re: Lets Talk Headlight Relays
« Reply #18 on: August 25, 2020, 05:17:21 AM »
CANBUS?
Didn't think any Guzzis had that, other than maybe the V85?

Quick question.
A couple of the Relays on the Stelvio have a Diode in them, to protect the ECU.
What's the criteria for using that type when adding Relays for other Circuits, if there is one?
I think it is silly to use a special relay with the diode built in when you could keep all the relays identical for interchangeability with a discrete diode.
I like the way they were wired back in the 2000 era with the diode separate. I have known the safety diode to pay off a few times when the owner accidentally connected the battery backwards
The bike will crank normally if it has a Bosch starter but never start because the ECU is powered down (pump won't prime either)
The early P8 ECU had the diode buried in the ECU, that wasn't a good idea either, it was possible to burn it out, don't ask me how I know.
The CARC bikes and all the V7s have CANBUS its used to communicate between the ECU and dash
« Last Edit: August 28, 2020, 12:35:26 AM by Kiwi_Roy »
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Offline Kiwi_Roy

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Re: Lets Talk Headlight Relays
« Reply #19 on: August 25, 2020, 05:38:27 AM »
Youíve got me thinking that I should put a few relays in my Eldovert, which I am presently wiring from scratch.  Where do I get the thing (donít know proper term) that the relays plug into?  It would be analogous to a fuse block.
Thats a problem I have had also, finding the right relay base especially when you have half a dozen relays like an EV with a mix of relays and fuses mixed together. I would try Digikey Electronics
I would also use a relay that one of the other Guzzi models use so they are easy to obtain spares.
For my old 72 Eldorado I used the old cube Bosch relays that mount on a tab with no base just spade lugs to connect where needed.
Again when putting relays inside the headlight bucket, there's no room for a base I just used the same Omron relays that the EV uses with a small aluminium strap to hold the relay and individual lugs for the wires, the  tails on the lamp socket are long enough to reach the relay socket.
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Offline Zoom Zoom

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Re: Lets Talk Headlight Relays
« Reply #20 on: August 25, 2020, 06:32:06 AM »
I certainly see the merit of adding a relay to the headlight circuit. For my GPS lead, I tied into the pilot light. Those feed wires are pretty small, and it just seems like a decent idea to take some of that current out of the switch gear. (V7III) Along this same line, when we were discussing charging issues in the other thread, and if I understood correctly, the alternator generates excessive heat if it is working too hard OR not working hard enough. Am I correct in that understanding??? Anyway, as a result, I have not pursued an LED headlight bulb as of yet. Of course that would reduce the current passing through the switch gear simply by doing that, but then we're back to the heat issue that you and Vagrant had to deal with.

Along these same lines, I do plan on adding a relay to the starter sooner than later. Again to reduce the current through the switch as a preventive measure. Weather it is imperative or not can be debated, but it certainly cannot hurt.

Back to the headlight. Would I understand that to do it right, a person would put a relay on both the low and high beam, as in two relays? (I'm no stranger to installing relays BTW.) I'm really interested in best practice here, not the how to.

John Henry
« Last Edit: August 25, 2020, 06:33:25 AM by Zoom Zoom »

Offline Kiwi_Roy

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Re: Lets Talk Headlight Relays
« Reply #21 on: August 25, 2020, 07:06:05 AM »
John Henry,
                 The problem with my alternator, a couple of the coils had a short in them, just a few turns I think this causes a massive local circulating current, The alternator could not hold its own, by the end of the day the battery was below 12.
I'm pleased to say with the new stator its holding 14.5 now while running and has 12.6 on a first start in the morning. The charger has been retired.
The LEDs as well as reducing the current also aren't so Voltage critical they are happy if they get 9 Volts, a relay would be wasted there IMHO

One or Two relays depends on which Guzzi you are doing I think, I have done it both ways.
Since all the modern Guzzis already have a Light Logic relay I suggested just one form C to select which beam but as you say it could be a pair, I don't believe either way is right or wrong.

On older Guzzis there was no headlight relay for example a California II had a massive unfused feed to the ignition switch, there I used a 40 Amp fuse to add some short circuit protection and picked up a feed from the hot (red) wire at the ignition switch with a pair of relays (the signal through the dimmer switch was switched by the ignition) Relays made a huge improvement to that light.
I also added a relay to take the place of the ignition switch contacts between the battery and the feed for the fuse block to take the load off the 40 year old wiring.
http://www.thisoldtractor.com/guzzi007/schematics/1981_California_II.gif
 
« Last Edit: August 26, 2020, 11:47:01 AM by Kiwi_Roy »
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Moto Guzzi - making electricians out of riders since March 15 1921

Offline John Warner

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Lets Talk Headlight Relays
« Reply #22 on: August 27, 2020, 08:43:25 AM »
I think it is silly to use a special relay with the diode built in when you could keep all the relays identical for interchangeability with a discrete diode.
I was more just wondering where/when you'd need to use a Relay with a Diode, I suspect it's only when the Relay is directly controlled from the ECU?


Quote
The CARC bikes and all the V7s have CANBUS its used to communicate between the ECU and dash.
Ah, OK, so not full CANBUS then.
That explains why there's so many damn Wires all over the Bike!   :grin:
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Offline Kiwi_Roy

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Re: Lets Talk Headlight Relays
« Reply #23 on: August 28, 2020, 12:47:54 AM »
I was more just wondering where/when you'd need to use a Relay with a Diode, I suspect it's only when the Relay is directly controlled from the ECU?
 
Not really, here's an example.
http://www.thisoldtractor.com/guzzi007/schematics/2000_Jackal.gif
This is not an internal diode but it could have been
The Safety Diode 51 is not really wired to the ECU its wired in series with the ECU relay that closes to power up The ECU
The Safety Diode is there to check the polarity of the 12 Volts, if its wrong the diode will prevent the relay from closing and putting the wrong polarity on the sensitive ECU components.
I had a guy contact me because his bike was cranking over normally but no spark. He had one of those yellow batteries with 4 terminals and had put it in backwards, the Safety Diode saved the day.
As I said earlier if I wanted a relay with a diode I would use a standard relay and add a separate diode.
BTW he had a Bosch starter with wound fields, they don't care what the polarity is, they always go the same way, a Valeo with permanent magnet fields would try to run in reverse.
« Last Edit: August 28, 2020, 12:53:31 AM by Kiwi_Roy »
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Moto Guzzi - making electricians out of riders since March 15 1921

Offline John Warner

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Re: Lets Talk Headlight Relays
« Reply #24 on: August 28, 2020, 05:39:58 AM »
That makes sense, thanks again Roy.
I have one of those Motobatt 'Quadflex' Batteries, very useful for adding extra Circuits.
The Terminals are marked/colour-coded clearly enough, maybe he fitted it in the dark! 😁
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