Headlight Relay Harness
#41
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Just out of curiosity, why didn't you pop a diode in there between the high and low relays so you can run dual beams? (lows stay on with highs, but not vice versa)
PS- I was still getting 12.4ish volts at my factory harness, however the amperage was significantly less than after I rewired with 12awg I'm sure. (I'm running dual beams, Osram Nightbreaker bulbs in Hella E-code housings)
Will be doing a proper HID retrofit in the future, though. The retro I did on my M3 has me spoiled. LOL.
PS- I was still getting 12.4ish volts at my factory harness, however the amperage was significantly less than after I rewired with 12awg I'm sure. (I'm running dual beams, Osram Nightbreaker bulbs in Hella E-code housings)
Will be doing a proper HID retrofit in the future, though. The retro I did on my M3 has me spoiled. LOL.
To measure voltage drop accurately, you have to take the reading at the bulb while it's on and compare it to the battery voltage. I didn't measure mine since I was upgrading the wiring for high-watt bulbs anyway.
#43
The low beams stay on with the highs the way it is now...they shouldn't but they do lol. It has to be the bulbs. I spaced it before but that actually makes the total draw 310w with the high beams on. Still have almost 1000w of room before the cable reaches capacity though lol.
To measure voltage drop accurately, you have to take the reading at the bulb while it's on and compare it to the battery voltage. I didn't measure mine since I was upgrading the wiring for high-watt bulbs anyway.
To measure voltage drop accurately, you have to take the reading at the bulb while it's on and compare it to the battery voltage. I didn't measure mine since I was upgrading the wiring for high-watt bulbs anyway.
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#52
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Alright ill have to check them out. I just ordered my housing for my H4 upgrade and plan to upgrade the harness at the same time.
Thanks for the super quick reply
Thanks for the super quick reply
#54
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BUT if you want to go that far over the top you could use the original (or an aftermarket) connector with 14awg, cut off all but the last inch before the connector, strip off all the insulation and solder 10awg to the crimp part of the connector and the 1" on wire then heat shrink it.
however, IMHO (27years of aircraft/heavy truck/automotive wiring) if you have good connections at the light there is not a bulb on the planet that would cause issues with the 12"-18" 14awg pigtail coming off the headlight connector. you are not going to get any "bottle-neck" effect on your amperage running 100 or even 150 watts of 13.5vdc through a 14awg wire (which is rated at 15amps max or 202.5watts @13.5vdc over a 100' length).
#55
I used some 12ga and it was a bit too stiff and bulky and I think silly overkill. I think it is more the run needs to be short and the connections need to be clean. Regular high or low beam only draws 9.5 amp or so.
#56
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How many of the positive wires do you have connecting to the battery? Is it just one that splits off into the two relays or did you run a separate wire for each relay?
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If you're going to run hi/lo together as your high beams, each relay should have its own 12awg wire to the battery (assuming everything else is 12awg).
If you have one wire feeding both relays (again, assuming everything is the same gauge) and both relays are drawing power, the total draw effectively doubles for that section of wire in relation to the rest of the harness (downstream from the relays). This will cut the entire wiring harness' capacity in half. It will still work this way, but why build it half ass.
Also, I didn't illustrate this in my schematic, and I don't think I mentioned it anywhere, but my power wires are fused. Anything connected to the positive terminal of the battery should always be fused as close to the battery as possible.
If you have one wire feeding both relays (again, assuming everything is the same gauge) and both relays are drawing power, the total draw effectively doubles for that section of wire in relation to the rest of the harness (downstream from the relays). This will cut the entire wiring harness' capacity in half. It will still work this way, but why build it half ass.
Also, I didn't illustrate this in my schematic, and I don't think I mentioned it anywhere, but my power wires are fused. Anything connected to the positive terminal of the battery should always be fused as close to the battery as possible.
#59
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If you're going to run hi/lo together as your high beams, each relay should have its own 12awg wire to the battery (assuming everything else is 12awg).
If you have one wire feeding both relays (again, assuming everything is the same gauge) and both relays are drawing power, the total draw effectively doubles for that section of wire in relation to the rest of the harness (downstream from the relays). This will cut the entire wiring harness' capacity in half. It will still work this way, but why build it half ass.
Also, I didn't illustrate this in my schematic, and I don't think I mentioned it anywhere, but my power wires are fused. Anything connected to the positive terminal of the battery should always be fused as close to the battery as possible.
If you have one wire feeding both relays (again, assuming everything is the same gauge) and both relays are drawing power, the total draw effectively doubles for that section of wire in relation to the rest of the harness (downstream from the relays). This will cut the entire wiring harness' capacity in half. It will still work this way, but why build it half ass.
Also, I didn't illustrate this in my schematic, and I don't think I mentioned it anywhere, but my power wires are fused. Anything connected to the positive terminal of the battery should always be fused as close to the battery as possible.
After figuring the appropriate wire size, taking LENGTH in to consideration, I feel very comfortable that 12AWG is more than sufficient to power this unit at full power.
12AWG is rated at 20amps @ 12VDC at 100' of length. Being that mine is only 2.5' long we are in good shape.
If you were to put your theory into practice your wires from the relays to the headlights would have to be equal in length (i'm guessing they arent) or one headlight would be brighter than the other!
Thanks for the vote if confidence.......
#60
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Ok, thanks for the explanation. 12AWG is more than sufficient for my application and not to mention it is also cheaper than the 10. While we're on the topic of wiring which would be better: tinned or regular primary wire? I found a source for both with good prices and am just wondering if the tinned wire provides any advantage over regular wire.
Last edited by streetlancer; 01-05-2012 at 08:19 PM.