My Headlight Relay Project... [Archive] - Dodge Talk Community Forum


Click Here to Visit The Planets Largest Dodge Enthusiast Community




PDA

View Full Version Of This Page : My Headlight Relay Project...


bherder
01-12-2007, 11:45 PM
OK…. After fiddle-farting around on this for a couple months, I finally got my ‘Headlight Relay Project’ finished! I gotta’ say, it was well worth the time, effort, and $$.

Also, because I was curious, I checked the voltage that was going to the connectors at the headlights… Even with the engine running at high idle, I was only getting 11.5 volts to the headlights! Even though I've got a fairly new headlight switch, dimmer switch and cleaned the hell out of the bulkhead connectors, still a low voltage. I’m going to chalk it up to 27 year-old wiring.

Anyway, being as that is neither here nor there for all practical purposes...

I did mine a little different than from the websites I’ve seen on doing this..

First of all, being as I have a quad-light setup, it meant extra wiring, but that was no biggie.

My major deviation was probably the relays used. Instead of the nice pretty relays I’ve seen on the various websites, I elected to go with these big, ugly, relays that are typically used for things like trailer-hitch connections. These are the ones that look like old Furd starter relays, but are meant to be ‘on’ all the time. They are typically used for the connection that you would use for charging the battery in a travel trailer when it’s plugged in. I figured that if these relays are good enough to be on all the time with 50 amps running though them, they sure as heck ought to be good enough to run a set of headlights.
Besides, I already had one sitting on the parts shelf, so it was just a matter of picking up another one at NAPA.

I also decided I was going to run 10 gauge wire throughout. Call this a ‘quirk’ of mine, but I’ve always been in the habit of ‘overkill’ on stuff like this. When I rewire something, If I can’t arc-weld with the wires I’m using, I’m not happy :)
I also chose to put glass-tube type of fuses in the circuit, for two reasons…

A: So I would only have to carry the same type of fuses…

B: Because I couldn’t find any ‘blade type’ fuse holders at NAPA with 10 gauge wires. There may be such an animal, but they weren’t hanging on the shelf when I was there getting parts.

All the wiring and connectors are crimped, soldered, shrink-tubed and split-loomed.

My other sorta’ goofy way of doing this was to make the connections for the relays/headlights just spade terminals (Male and female). I did this for the very reason that:

A: I didn’t want to splice in plugs going from a 14 gauge wire to a 10 gauge harness. There would be no point of keeping everything 10 gauge if I did that.

B: IF …. For some reason…. Should anyone ever own this truck besides me… (Which I don’t see ever happening, but you never know, I might fall over dead tomorrow..) and should they ever want to hook it up back ‘stock’… It’s just a matter of unplugging a few wires and plugging the factory connectors back onto the lights. The ‘stock’ connectors (Other than the one I used for actuating the relays) Have been blocked off and wrapped with a quality electric tape to keep the crud out of them. My grounds are to the chassis, but since I’ve made six-ways-to-Sunday sure that I have more than an excellent chassis ground, I was not concerned about this. Besides, I’ve got so many wires running off of the (-) battery terminal already, I didn’t want to add anything else..

Anywho, the first pic is of the placement of the relays, nothing else hooked up.
Second pic is of all the finished wire harnesses..
Third pic is of relays with wiring hooked up..
Forth pic is a ‘before/after’ pic of headlight brightness. It doesn’t look like much, but at night, sitting behind the wheel, it makes a world of difference!

old tired rebel
01-13-2007, 09:35 AM
Thats Great too bad I only have single headlights.

LEVE
01-13-2007, 10:28 AM
I like the connector idea to return to stock if the truck is sold. I've a few questions about the project:


Can you post a schematic?
Are you using the OEM headlight plugs to just enable/disable the constant load relays?
What point are you using to supply the 12 volt voltate to the headlights?
Have you thought about using full Alternator voltage?
What did you do with the OEM sockets/plugs to keep corrosion from building up in the contacts?

charlie1935
01-13-2007, 11:33 AM
Beherder, I'm just like you on using bigger wire. Even down to my jumper cables made from 00 welding cable. They never even get warm. :gr_patrio

bherder
01-13-2007, 05:21 PM
I like the connector idea to return to stock if the truck is sold. I've a few questions about the project:

Can you post a schematic?

Sure! See attachment.. (BTW, I'm not a draftsman! ;) )

Are you using the OEM headlight plugs to just enable/disable the constant load relays?

Yup.

What point are you using to supply the 12 volt voltate to the headlights?

Where the battery cable connects to the starter relay..

Have you thought about using full Alternator voltage?

You mean unregulated voltage? I don't know for sure, but I'm guessing the headlights wouldn't last too long.. Wouldn't I be feeding it something like 17-18 volts?

What did you do with the OEM sockets/plugs to keep corrosion from building up in the contacts?

I wrapped the other ones up with electric splicing tape. You know that stretchy rubber type stuff....

L5wolvesf
01-13-2007, 08:39 PM
….
My major deviation was probably the relays used. Instead of the nice pretty relays I’ve seen on the various websites, I elected to go with these big, ugly, relays that are typically used for things like trailer-hitch connections. These are the ones that look like old Furd starter relays, but are meant to be ‘on’ all the time. They are typically used for the connection that you would use for charging the battery in a travel trailer when it’s plugged in. I figured that if these relays are good enough to be on all the time with 50 amps running though them, they sure as heck ought to be good enough to run a set of headlights.

Hey Herder - looks good.

A question - what is the minimum rating relay needed to do the headlights?

Thanks,

Chump
01-14-2007, 12:10 AM
bherder...NASA will be proud of you! I have been playing around with 2 other ideas for the relay system...one would be completely pluggable at the firewall and use the existing wires...this is for an experiment to see what the voltage drop might be...the other idea was to use a male plug on the end of the original 3 pin headlight connectors and use the exitting wiring to activate the relays. This would also make the wiring pluggable. Just some more thoughts.

Did you measure your voltage at the headlight after the conversion?

Might want to post some part numbers so that any one that wants to follow your conversion can do it easier.

I like the idea of keeping the fuses the same and you could also install inline circuit breakers that reset automatically.

bherder
01-14-2007, 11:01 AM
Hey Herder - looks good.

A question - what is the minimum rating relay needed to do the headlights?

Thanks,

I have no idea.. that's another reason I went with these 'elephant gun' relays. I wanted to make absolutely sure I had enough 'relay' ;)

I would guess that being as the fuse for the factory setup is 20 amp, that would be my starting point, had I been trying to scale this back a bit.
On the other hand, being as when you do this, you're dividing the low/high beams in to basically two separate circuits, you might be able to go lower.. I don't really know.

Hey there Chump! You're the resident electrical guru around here... What say ye?

bherder
01-14-2007, 11:19 AM
bherder...NASA will be proud of you!

Thanks! ;)

I have been playing around with 2 other ideas for the relay system...one would be completely pluggable at the firewall and use the existing wires...this is for an experiment to see what the voltage drop might be...

That is an interesting idea....


the other idea was to use a male plug on the end of the original 3 pin headlight connectors and use the exitting wiring to activate the relays. This would also make the wiring pluggable. Just some more thoughts.

Do they make such a plug? Os this something you'd have to make on your own?

Did you measure your voltage at the headlight after the conversion?

Yeah, (Forgot to post... Like I forgot to draw in the fuses on my schematic ;) )

13.7v with engine running.

Might want to post some part numbers so that any one that wants to follow your conversion can do it easier.

Not much to list...

The relay was a NAPA (ECHLIN) ST85 ($40.00 - Ouch!)
Didn't save the cards the fuse holders came on, but just your standard BUSS 30 amp fuse holder (I didn't use 30 amp fuses in the finished product, but the 30 amper was 10 guage wire)

Also, the relay I already had only had one terminal to engage the relay, the body being grounded. The new one I bought (Same part #) had two terminals, which was no biggie, I just had to make a short grounding wire for it..

Anyway, the rest was just wire, terminals, solder, shrink tube, split looms and plastic zip ties..

I like the idea of keeping the fuses the same and you could also install inline circuit breakers that reset automatically.

I thought about breakers, but was trying to keep cost sorta' kinda' under control. I can't ever see popping a fuse or breaker on this.. But you never know..

L5wolvesf
01-14-2007, 10:37 PM
I have no idea.. that's another reason I went with these 'elephant gun' relays. I wanted to make absolutely sure I had enough 'relay' ;)

Hey there Chump! You're the resident electrical guru around here... What say ye?

So I could just use a Ford starter relay?

Thanks,

Chump
01-14-2007, 10:50 PM
So I could just use a Ford starter relay?

Thanks,


You can use a 20 amp Bosch Relay like these if you like...
www.partsexpress.com and search for relay

bherder
01-16-2007, 09:05 AM
So I could just use a Ford starter relay?

Don't know if you could or not. I don't think they're meant/designed to be constantly 'on'... I'm going to guess no.
The contacts end of it should be no prob as it is designed to allow enough amps to be pulled through it for a starter, I'm just not sure about the actuating end of it. If it can be 'on' for hours at a time, rather than a few seconds.. (Of course here is where someone will probably post "Oh, I've been using those for 20 years, no probs!" ;) )

LEVE
01-16-2007, 10:20 AM
You could use a Ford Starter relay, but they're not rated for a constant load.

http://www.oldengine.org/unfaq/u939.jpg

That's not to say they won't work, but why pay the costs? You could also use the less expensive generic headlight 30 amp relays They're $4 at NAPA:

http://partimages2.genpt.com/partimages/371702.jpg (http://www.napaonline.com//MasterPages/NOLMaster.aspx?PageId=470&LineCode=GRO&PartNumber=448405&Description=Lamp+Relay+-+Fog+%26+Driving)


My personal choice to do this upgrade would be to go to a wrecking yard, and pull out a set of these headlight relays and their sockets (with about 8" of the wiring harness). The cost would very reasonable and the parts available anywhere for cheap.

cjbarron5
01-20-2007, 01:18 PM
bherder can you "cook" up a 2 headlight system for us less electrical savy people?

bherder
01-20-2007, 03:05 PM
It should be the same, minus the power lead and ground on the extra set of high beams... Just 'white-out' that part of it, and you should be good to go ;)

Anyway, I just redid the schematic for you, and cleaned it up a little bit.
I also put in the fuse that I forgot to draw in the first time.
Now, I just put in one fuse to show where it goes. I used 2 fuses (One for each circuit) because should something happen (It shouldn't, but "never say never", right? :D ) if one circuit blows a fuse, hopefully the other circuit will work, and some headlights are better than no headlights..