hey guys I have a question about diode's... hoping you guys can school me a bit about them.

I want to install a relay for my headlights... I am going to need to install two of them, one for my low beam circuit and one for my hi beam circuit. My truck has daytime running lights which are on all the time while you drive. The DTRL module is spliced into the h/l circuit and operates the hi beam circuit at a lower than battery voltage... it is a pulsing battery voltage that I think averages about 7 volts.

Now I know how I want to install the relays but I think I might have a problem because of the DTRL's... I was planning to get my relay switching power from my hi/low beam switch on the floor... it's before the DTRL module and the splices that connect it to the headlights. The problem is when I check the voltage at the switch I'm getting 7 or so volts while the DTRL's are on... I'm concerned that the 7 volts will be enough to switch on the relay and thus turning on my hi beams while I drive with my lights off and the DTRL's on...

So my question is... is 7 or so volts enough to switch on my relay?, I kinda think it is. Can I install a diode after the splice I need for the relay? And if a diode is the answer what kind of diode do I need and whare can I get one? Any thoughts and comments are appreciated.

Thanxs,
Corey

 

Good site for you is The Electonics Club . Components then diodes.There a circuit is displayed with diode protecting a relay this is needed in some circuits. Notice how you need to get to both sides of the coil. Most times a diode is used to change ac to dc or to keep current going in one dirction.

 

Yes you could use a diode. You can install it and use it sort of like a "check valve", letting the current from the dimmer switch pass through to the original circuits in the truck, but block the voltage coming backwards from the trucks original wiring.

The diode will have a band on one end. Cut the original wire coming out of the dimmer switch, and insert the diode with the band going out to the circuits, and the plain end toward the dimmer switch. Then splice your added wire on the no band side or the dimmer switch side of the diode.

What I am wondering is why don't you just cut the original truck wiring to the dimmer switch, and then run new wiring to the relays? Isn't the drl circuit powered from somewhere else beside the dimmer switch? For a test, unplug the dimmer switch and see if the drl's still work. If they do, you would not need the diode.

 

Well... after reading your post franklin2 I ran... literally... out to my truck to see if, like you suggested, the dtrl's operate with the dimmer switch unplugged... and they do! Dam! I sure made this more complicated than it had too... I feel kinda stupid now... but very grateful for your very wise suggestion.

With that suggestion comes another question which I would like your comments on... I think I would still have to wire in the old low beam circuit to the new feed from the relay as on the wiring diagram I have there is a splice in the low beam circuit that goes to the dtrl module which I would assume turns the dtrl's off when the light are on... or am I making this too complicated again?


Corey

 

I am looking at this diagram
http://www.autozone.com/images/cds/g...3d800a3a5c.gif
and there may be a problem. Looking at the diagram, it seems the drl module feeds the dash highbeam indicator. If that is true, then you might have to do your diode trick and keep the drl input from the dimmer switch hot to make the little blue light in the dash work.

As far as the module turning on and off with the lowbeams, I think you are correct there too, since if it didn't the lowbeams would be on and the highbeams would be on in drl mode. So I guess you should leave the dimmer switch wiring hooked up to the original truck wiring, and use the diode in the highbeam side like you originally planned.

These diodes should be big enough. If they run a little warm, you can run two side by side so they will share the load.
6A, 50V Rectifier Diodes (4-Pack) - RadioShack.com

 

as per alldata (which doesn't give the whole view like the diagram you gave me, thank you!) my hi-beam indicator is feed directly from a gy/w wire from the DTRL module, it goes right to the indicator with no splices or feeds from anything else. But if I splice a feed to the old portion of the hi-beam from the new hi-beam relay then that would in theory give me the signal to turn on my hi-beam indicator and power the dtrl's... there is only one wire spliced to the hi-beam power wire to the dtrl module which means that one wire powers the dtrl's and and recieves power when the hi-beams are on... which I think would turn on the indicator.

So too clarify everything...I would have to cut the hi and low beam wires from my dimmer switch and use them as my relay switching power. Then make sure that the old head light circuit is feed or spliced into the new power feeds from the hi and low-beam relays thus giving the dtrl module its signal or feed to power up and power down the dtrl's, and power the hi-beam indicator when I turn them on... I think that works?...

I just want to say that there is a hd headlight harness that is available for trucks like mine. Most say that they are not compatible with trucks that have dtrl's... others say that they are compatible but when you look at the install instructions they ask you to unplug the dtrl module and zap-strap the loose plug wire... not exactly legal up here in canada and not the way I would like to do this mod... if someone knows of a complete "kit" that plugs in to the existing harness like most claim to do, and keeps the normal operation of the dtrl's feel free post it.

Franklin2... I feel like I owe you a beer... or 20! feel free to comment on what you think about all of this but I feel like I'm asking too much from you... I think I now have the tools and information to finish this project off now that I have your insight. I've been thinking about this mod for a while and although it's not a critical issue I'm glad that I figured it out with your help. thank you again... it is people like your self who without compensation give there time to help others and in turn make this site so great.

Thank you!
Corey

P.S. I'll post my results.....

 

Looks like you have it figured out. I didn't know how much wiring modifications you were prepared to make, but it sounds like you are willing to do what it takes, and I think it will work.