Sport Light Conversion - Need Diode Recommendation

[brn2fsh]

Hello,



I am doing the sport light conversion on my 97. I would like to install 2 diodes in the circuit I have planned but do not know what size/type of diode to use. As part of my wiring scheme, one particular relay will have two inputs (two separate wires) to pin 86. One input will be the “high beam on” and the other input will be the “low beam on”. I do not want current to back feed into the “low beam on” input when the “high beam on” input is energized and vice versa so I plan on installing a diode on each of these inputs. I am thinking about using a 1N4001 diode which is rated for 1 amp. Will this work? If not, please offer any suggestions.



Thanks,



Scott

 

[Gary - K7GLD]

I'm considering doing the same thing on mine - yes, the diode approach should work as long as the voltage and current ratings are adequate for the relay current draw. I'm not familiar with the particular diode you refer to, but diodes are cheap, so leave yourself plenty of margin - a 50 volt at 5 amps or so diode would be what I would look for.



In these type instances, overkill is a GOOD thing!

 

[brn2fsh]

Gary,



The 1n4001 is a 1 amp/50V Diode. It is commonly used in automotive applications. I don't know the current draw of the coil in the relay either but it should not be very much. I'm thinking it is less than 1 amp.



I'm no electrical expert but you got me to thinking. Rather than sizing the diode to the current draw of the rely, maybe the diode should be sized to match the fuse that is protecting the headlight circut. That way, if there is a short in the circuit, then the fuse would melt before the diode. If this approach was taken, then the diode would need to be capable of 20 amps or greater.



Scott

 

[Gary - K7GLD]

Gary,



The 1n4001 is a 1 amp/50V Diode. It is commonly used in automotive applications. I don't know the current draw of the coil in the relay either but it should not be very much. I'm thinking it is less than 1 amp.



I'm no electrical expert but you got me to thinking. Rather than sizing the diode to the current draw of the rely, maybe the diode should be sized to match the fuse that is protecting the headlight circuit. That way, if there is a short in the circuit, then the fuse would melt before the diode. If this approach was taken, then the diode would need to be capable of 20 amps or greater.



Scott

Biggest cause of diode failures, is not allowing for circuit spikes and surges - some of those CAN get pretty high. I looked on the Bosch relays my wiring kit provided, but no reference to coil current, but probably less than an amp.



I'm working from memory here, so don't shoot me if I'm wrong - and I haven't drawn this out on paper - but if you are using the stock headlight wiring to key the added relays, remember that Dodge switches the NEGATIVE leads, not the positive.



In my case at least, I had figured a single diode from the hi-beam relay coil terminal to the lo-beam coil would be all that's needed to energize both hi AND lo beams when hi beams are selected - but cause only the lo beam relay and lights to energize when lo-beams are selected. But as I said, I haven't really dug into this yet, so it's all off the top of my (bald!) head... :-laf

 

[brn2fsh]

Gary,



You are right about the newer trucks being negative switched. My truck, being a 97 is positively switched. I don't know when dodge changed from positive to negative switched but I am thinking around 2001.



In my case, I want to use only one relay to trigger to low beams in all circymstances. The single relay will be fed by both the low beam and high beam on feeds. I want to put diodes in each feed so that current doesn't flow back into one feed when the other is energized.



I looked into the diodes a little bit. I found a 3 amp diode, Model: 1N5404, that has a ultimate 200A surge and a Peak Inverse Voltage of 400. The 3 amp continuous should be adequate for the relay coils and the 200 amp surge protection should be aequate for our trucks.



Scott

 

[Gary - K7GLD]

Sounds good Scott - let us know how it turns out!

 

[Thomas]

... I don't know when dodge changed from positive to negative switched but I am thinking around 2001...

I think you'll find the negative ground appeared model year 1999. Model year 1999-2002 Ram 2500's & 3500's use the same BriteBox®.

I don't know what relays you are using. The OEM Bosch micro-relays in the PDC flow 200 milliamps through their trigger coils. As mentioned, overkill should not hurt.