Hi/Lo Beam Relay Wiring Question

[ArdWrknTrk]

I'll bet you felt a lot safer with your son driving at night after that.

[Gary Lewis]

If I remember right Sylvania had a class-action against them for the short life of their SilverStar headlights. I wonder if you had a pair of them?

[Nothing Special]

ArdWrknTrk wrote

I'll bet you felt a lot safer with your son driving at night after that.

I sure didn't feel good about how I had been (unknowingly) putting him in an unsafe situation driving it before that!

Gary Lewis wrote

If I remember right Sylvania had a class-action against them for the short life of their SilverStar headlights. I wonder if you had a pair of them?

I don't remember what lights they were.  It was about 5 or 6 years ago for what that's worth.

[Angelo Voltura]

I can also attest to how good the harness is. My 95 with a bull clip has it, my 79 has it, my dads 85 has it on his regular lights and snow plow lights and my buddy put it on his 86 Dodge he had.

Excellent upgrade.

[old55pete]

CONTENTS DELETED

The author has deleted this message.

[Gary Lewis]

It is amazing that the manufacturers didn't do that themselves.  Yes, when multiplied by the # of vehicles the cost difference turns into big bucks, but they still traded our safety for their profit.

[old55pete]

CONTENTS DELETED

The author has deleted this message.

[ArdWrknTrk]

I had (and still have half of) the LMC kit.
I'm pretty sure that it's 14Ga. On the hot side.
They use 40A mini relays with integral mounting tabs.

[Nothing Special]

old55pete wrote

....  The headlights have always been dismal. So bad that most folks don't notice that I have the brights on...…….lol

I know you were talking about your Dodge.  But the headlights on Ford pickups always seemed to be pretty bright when the trucks were (relatively) new.  I don't know if they'd be considered bright by today's standards, but back in the '80s if I was being blinded by oncoming headlights it was either someone with their high beams on or else it was a Ford pickup.  And I know the low beams on my '85 F-250 did draw a few high beam flashes from oncoming traffic who thought I must be using high beams.  So I certainly see why Ford at least didn't think it was necessary to spend any more on headlight wiring back then.

[old55pete]

CONTENTS DELETED

The author has deleted this message.

[Gary Lewis]

Even if #14 wire is used a harness will be an upgrade.  That's because the current has far less distance to traverse - usually directly from the battery to the relay to the right headlight and then across the radiator support to the left headlight.

Compare that to running back into the cab, across the cab to the switch, then back across the cab and out to the right headlight.

[kramttocs]

Can start a new thread for this if needed but...

On the FTE Whiter White, Brighter Brights article he shows the optional Hi Beam Flash and Lo Beam Toggle (always on). Your guess is a good as mine if I'll ever use them but I like the idea and since I have the room in the control panel I am printing up, might as well do it.

Since after installing the standard relay mod the drivers side portion of the factory harness is just a dead end, I am wanting to use that for my optional switches as it doesn't require cutting/slicing into anything new.

This diagram is what I am thinking. Important to note that I am re-purposing a relay icon to be my momentary switches. I just couldn't find a better fitting object in the software. So the 'relay' is now the switch as well as the led indicator. These are the two 'relays' on the left hand side. The right hand side ones are the actual relays. Also I am using both add-on switches as momentary and independent of the headlight switch unlike in the article where he had the low on a toggle after the headlight switch.
The diagram below is hard to see so you can go here  for a better view.



Some questions:

1. I am only wanting the switch leds to light when the switch is being pushed. Not when the headlights are activated via the factory switch/dimmer. I added two schottky diodes in the diagram above. Is that the correct usages of them? What amp value should I use?

2. The add-on switch circuit I have set to use a 3A fuse. This fuse will actually feed the 5 switches I have that all go to relays (no direct load on them). The switches I have are 5A and I made a 12ga to 18ga harness (below) so from the 3A side the 5A switches should be protected.
What about from the headlight factory switch side though?
Do I need to be concerned with a short on that side that would hit the switch before the fuse link goes? Or would this only be an issue if there was a short AND I pushed the momentary switch, correct? At which point the 3A would blow so the 5A switch would still be protected?
If there was a short in the wire between the 3A fuse and the switch - if I press the switch AND the headlight factory switch was on, the 3A would blow but the switch would also fry before the fuse link goes, correct? Or would the diode blow?
Ultimately it sounds like I should put a fuse between the diode and the factory headlight switch but was trying to avoid inline fuses that won't be located in my fuse block.

Getting back to the diode amp question - does it need to match the fuse so should it be a 3A diode?

Sorry, I know that's a lot of questions thrown in there but just trying to work it out in my head.

[Gary Lewis]

You are causing me to THINK, and that hurts:

1. Yes, that looks would work, but I don't see the need for a schottky diode.  Those are just fast diodes.  As for amperage, just enough to pull in the relay, which is less than an amp.

2. Yipes!  To protect the diode it needs to be larger than the fuse.  But unless you are going to be pushing a lot of buttons at the same time, 3 amp may be enough fuse.  At 500ma/relay, as many are, you can do ~6 at a time.

3. Yes, I know you didn't have a #3 identified, but it is there nonetheless.  From memory, the headlights are served by a 16ga fuse link.  (L?)  (Don't you wish that was a fuse?  With the load being carried by the headlight relays that fuse could be fairly small.  )  You really can't protect your wiring here unless you make it #12, which is enough to carry the current supplied by that fuse link.  But, Ford didn't really protect the wires running to the headlights as they are way smaller than the fuse link.  So maybe that's a risk you have to take.  Your wires will melt, but long before the switch burns, in my estimation.

Yes?  No?

[kramttocs]

Oh man, I really do wish that was a fuse there now. I may end up switching mine over after you get all the kinks worked out

Appreciate the response - I do figure some of this will just have an acceptable risk tied to it. Especially since I believe the only risk is when there is a short and both the momentary switch and headlight switch are on at the same time which should be unlikely.

You are correct about the 16ga headlight wiring.

So thinking the only thing to change would be the type of diode? Would a 1N5404 be what I need?

[Gary Lewis]

Yep, that diode should work well.  And at $.43 from Digikey they are cheap, except they don't have them in stock.  

Yes, a fuse is sounding better.  

[kramttocs]

Just to wrap up my previous posts-

Got the 3A diodes in today. Since I am using metri pack 280 connectors between the driver's side headlight wiring and the wiring that will go to the dash switches, decided to make a jumper that I could easily swap out between them. Also trying to avoid any hidden fuses or things like diodes tucked up in the dash if possible.
Made 3 identical length short pieces- two with the diodes and the pass through ground.


Snapped them into a male and female mp280 connector so there was barely a gap between where they butted up against each other and then taped the together.

This will go down near the drivers side turn signal bulb. Don't figure the paint will last too long but since I had it handy...

[Gary Lewis]

Well done, Scott.  

Similar to your diode symbols on the tape, I've been considering how to mark various things I'm doing.  As previously said, I hope to be able to figure out how to incorporate my PDB wiring diagram into the EVTM's page to make it obvious.  But I'm also trying to think of how to mark components.  And two thoughts just came to mind when looking at what you've done:

 

In the case of something like your diodes, I have a label printer and I could print a label that either went all the way around the thing or three labels that went where you have paint.  And then cover that with clear heat shrink.

For the PDB, maybe create a diagram that replicates the layout of the fuses, relays, and diodes and identify each one, then print that out and laminate it.  Cut that out and place it inside the PDB.

Thoughts?

[kramttocs]

Great ideas! Never even thought about clear heat shrink. Going to have to get me some of that.
Your plan sounds ideal to me -do the heat shrink on less than obvious things like the diode itself but put all the detail in the laminated schematic. The schematic will be the most useful part but having points of reference on the actual components as you navigate along the wiring would have some benefit.

[Gary Lewis]

I've not used clear heat shrink, but I've seen where it has been used and it was effective.

However, I think I may have misled you.  While I do plan to incorporate the PDB's wiring into the proper page from the EVTM, that's not what I was thinking of laminating.  That's because I don't think it could fit in the PDB and be legible.

Instead, I am thinking I'll lay out where all the fuses, relay, and diodes are in the PDB, and ID them.  Do, the fuse in the upper right corner, which the lid shows simply as Fuse 6, will be shown as the Start Fuse.  That I think I can laminate and either place in the PDB or, hopefully, glue to the inside of the PDB's lid.

[kramttocs]

Ah, I follow now. Yeah, I was picturing something like a folded up map (or small book )  in of those adhesive-backed plastic sleeves stuck inside the pdb lid. Having them labeled by application would be nice.