Jump to content
Sign in to follow this  
Grum

Headlight Relay wired wrong!

Recommended Posts

Hi All.

Have noticed Honda seem to have got their wires crossed! The Headlight Relay isn't doing what its supposed to. All the heavy current (whatever that is) is going through the Dimmer Switch or the Flash Switch (not shown) when Hi beam selected, see below, the main circuit diagram also matches the simplified drawing. Think it should be wired like the modified bottom drawing. Could this mean the Dimmer or Flash Switch may burn out prematurely? UPDATE - Have confirmed on the bike that the Headlight Relay is wired per drawings, ie all current including relay coil current is flowing through the switch - crazy use of a relay!!

Just for info.

Cheers.

Grum.

VFR_Headlights001.jpg

VFR_Headlights003.jpg

Share this post


Link to post
Share on other sites

Are you sure this is how it is wired on the bike, and not just a documentation error?

What's the point in having a relay if the coil and switch are wired to the same point?

Share this post


Link to post
Share on other sites

That is clearly not a true electrical schematic.  It's more of a basic representation of the parts and circuit.  (although it's odd that they didn't include the 'flash to pass' switch)

Obviously nobody would ever plan and assemble a relay that way. (not to mention the lo side of the dimmer switch goes nowhere!)

 

Don't worry about it Grum, I'm sure it's wired correctly and will last for years. :smile:

  • Like 1

Share this post


Link to post
Share on other sites
On 15 April 2017 at 7:08 AM, DriverDave said:

That is clearly not a true electrical schematic.  It's more of a basic representation of the parts and circuit.  (although it's odd that they didn't include the 'flash to pass' switch)

Obviously nobody would ever plan and assemble a relay that way. (not to mention the lo side of the dimmer switch goes nowhere!)

 

Don't worry about it Grum, I'm sure it's wired correctly and will last for years. :smile:

Hi DriverDave, and All.

Sorry DriverDave, I would like to agree with you, BUT, believe or not the bike IS wired this way, both the simplified and main circuit diagrams reflect this. I physically checked the bikes wiring today. 

Looking at the small wire gauge to the relay, it would appear that relatively small current is drawn, which might not cause an issue with the switches, BUT, I have never seen a relay wired like this, Honda may have well not included it, and simply wired it direct from the switch to the LED Driver keeping things simple?? :comp13:

Cheers.

Grum.

P.S. It would be normal for the dimmer switch to have a side going nowhere, as the default is LO Beam, the system only needs to know when HI Beam is selected.

Share this post


Link to post
Share on other sites
c3611d939bb44c0b64c6595d0a216fc2.jpg


Sent from my iPhone using Tapatalk

Ahh yes, it all makes sense now... :P


Sent from my iPhone using Tapatalk
  • Like 1

Share this post


Link to post
Share on other sites
12 hours ago, Quibble said:


Ahh yes, it all makes sense now... :P
 

 

I'm going in! (famous last words)

  • Like 2

Share this post


Link to post
Share on other sites

Hi All.

Sorry to bore some of you I know it's not the most interesting of topics, but coming from an electrical background I am intrigued by the strange wiring of the Headlight Relay and the potential for switch damage. 

After checking the bike and seeing the small wire gauge used in the circuit, reckon the switches should be fine.

As to the strange relay wiring, perhaps the answer might lie in the mystery box - LED Driver??

Cheers.

Grum

Share this post


Link to post
Share on other sites

May be a long shot, but is there some nonsense piece of regulation which says high beams must be powered via a relay??

  • Like 1

Share this post


Link to post
Share on other sites

Will have a look at my manual when I get a chance.  The load through the wires will be a lot lighter than conventional bulbs.  You must also remember the newer thin wall wires can handle more current than the wiring used in older bikes. 

  • Like 1

Share this post


Link to post
Share on other sites
On 4/15/2017 at 7:03 PM, Grum said:

Hi All.

Sorry to bore some of you I know it's not the most interesting of topics, but coming from an electrical background I am intrigued by the strange wiring of the Headlight Relay and the potential for switch damage. 

After checking the bike and seeing the small wire gauge used in the circuit, reckon the switches should be fine.

As to the strange relay wiring, perhaps the answer might lie in the mystery box - LED Driver??

Cheers.

Grum

 

Being no stranger to electronic circuits this is a little bit of an eyebrow raiser to me too.  I've given this a little thought...

 

So first of all we know that the LED headlamps are not nearly the current draw of its halogen predecessors.  So the demand on the wiring isn't nearly as substantial as it would have otherwise been.  If you're curious, check the DC current draw from the headlamp unit on high-beams, then check the size of the hookup wire against an ampacity chart.

 

The other thing is that the way this is set, you engage the high-beam switch, which closes the relay, which then allows the full high-beam supply current along with coil current to flow through the switch.  This means that at engagement time the switch is only handling coil current.  Therefore there would only be arcing concerns (and the related lifetime concerns re the switch) at disengagement time.

 

 

  • Like 2

Share this post


Link to post
Share on other sites

Hmm, that is curious.  I agree with the above assessment that the arcing concerns may only occur at disengagement depending what kind of reactive load is presented (capacitive and inductive load presented by the LED driver box).  I would be curious how much current actually flows through that switch - be careful with a meter though, you could easily damage it if the inrush current is high. 

 

We don't know what the LED driver box actually has connected to that input, it could be another internal relay or the gate(s) of a MOSFET(s).  I would also be hesitant to separately wire the supply to the relay contact since downstream circuits in the LED driver may be expecting a slight voltage drop from the headlight switch.

 

This is all conjecture at this point, since the switch and relay are powering a "black box" of unknown operational characteristics.  We can probably surmise, based on the non-standard use of the relay, that this black box load is not analogous to an incandescent headlight.

  • Like 1

Share this post


Link to post
Share on other sites

There's a discussion in another thread (front brake hose) that ended up mentioning engineers (and lawyers).

 

What's interesting about engineers is what happens when you put them through Lean Six Sigma training.

 

This looks like it could have been done to save a few feet of wire and employ slightly smaller connectors...

  • Like 1

Share this post


Link to post
Share on other sites

LOL, I started a green belt certification course back when I worked for Honeywell around the time of the GE acquisition that was blocked by the EU.  After the deal fell through, I made sure my other job responsibilities prevented my completion of the course.  Some of the content was reasonable, but you are right.  The course emphasizes the maximization of profits within "acceptable" failure margins.  A lot of the problem comes from the definition of the failure margins.  It has a good heart, if you don't start with a fixed failure margin but instead design to just before a point of diminishing returns.  Remember though, repairs are big business so a company building things "to last" is not necessarily in the best interest, especially when your customers want to minimize initial purchase costs.  OK, I'm going to stop now since this is hugely OT and I could talk for hours about the subject.

  • Like 2

Share this post


Link to post
Share on other sites

Thanks guys for your input, glad there are a few others out there as curious as I am as to the strange wiring of the Headlight Relay. I have a theory I'd like your experienced thoughts on.

 

As the headlight Hi Beam switching wiring is very small gauge, suspect the Hi Beam input to the LED Driver is only a Logic State!

AND, as the LED Driver produces constant current high voltage DC to drive the LED arrays, could the Relay Coil provide a protective low impedance path to ground in the event of an internal failure of the LED Driver, perhaps sending hi voltage zap onto the Hi Beam select line with the potential of blowing the tits off the Combination Meter?

Just a thought.

Cheers.

Grum.

Share this post


Link to post
Share on other sites
On ‎4‎/‎15‎/‎2017 at 9:44 AM, mikeswe said:

 

I'm going in! (famous last words)

Leeeeroyyyyyy Jenkinnnnnss!!!   :D

Share this post


Link to post
Share on other sites
5 hours ago, Grum said:

Thanks guys for your input, glad there are a few others out there as curious as I am as to the strange wiring of the Headlight Relay. I have a theory I'd like your experienced thoughts on.

 

As the headlight switching wiring is very small gauge, suspect the Hi Beam input to the LED Driver is only a Logic State!

AND, as the LED Driver produces constant current high voltage DC to drive the LED arrays, could the Relay Coil provide a protective low impedance path to ground in the event of an internal failure of the LED Driver, perhaps sending hi voltage zap onto the Hi Beam select line with the potential of blowing the tits off the Combination Meter?

Just a thought.

Cheers.

Grum.

There would be a semi conductor or something else in the way making sure it couldn't get back the way it came.

Share this post


Link to post
Share on other sites

The reason I think there is more to it than a semiconductor is the use of a relay.  That relay is rated to 20A, which would be MASSIVE overkill for input to a logic circuit.  Even if supplying voltage to a power MOSFET gate, where you will have some input capacitance, a relay would help with the input current spike; but why spec one so robust?

 

I have 2 thoughts on the issue:

1.  Bulk pricing - all 6 relays on that bike (next to each other on the wiring print) are the exact same part. 

2.  Spare parts - you are on the road and you lose a critical relay (Engine Stop, Fuel Pump, etc...) you can sacrifice the high beams to get yourself home.

  • Like 3

Share this post


Link to post
Share on other sites

Um, wouldn't that coil-connection ground the entire relay so it would never have any signal on the input, I mean we're talking DC here aren't we?

 

/R

Share this post


Link to post
Share on other sites
9 hours ago, RhINO said:

Um, wouldn't that coil-connection ground the entire relay so it would never have any signal on the input, I mean we're talking DC here aren't we?

 

The relay coil is a resistive load, not a short-circuit.

 

By short-circuit I mean a path with essentially zero resistance, like a piece of hookup wire.  We'll ignore values of thousands or hundredths of an ohm for now.

 

Polarity does not really matter except the "ground" concept would be different or absent.

 

Fused supply to the relay coil is controlled by a switch.  Electrical current goes through the fuse (short-circuit), through the switch (short circuit when closed, else open circuit), through the coil (DC mostly resistive load), probably around 75 Ohms through that coil if my Google-fu is good, then from there to ground.  That 75 Ohms means about 184 mA with a healthy 13.8 Volt supply.  Hardly a short, much less substantial load.

 

And that's usually the idea of an automotive relay.  You use a low-current set of contacts (like the handlebar switch with its small contacts and relatively small gauge wires) to control the flow of a larger current with the heavier contacts in the relay, and with larger wires and larger fuses, etc.

 

 

  • Like 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

×