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Old 07-12-2005, 08:48 PM
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Headlight amps and fuse size?

I have converted a street rod to halogen headlights and ran the wiring straight from the switch through the dimmer to the headlights with no relays -- lights flicker and go out after 5 minutes. I understand this is from a thermal circuit breaker in the Kwik wiring kit.

So, guess I need high beam and low beam relays, fuses or fusible link, primary power feed to relays, and a terminal block. My battery is located in the trunk. How do I size these components?

1. relays - I have Bosch 30/40 amp relays available with 18 and 14 gauge leads, I think -- these seem to be the relays of choice.
2. fuses - what amps do halogen bulbs draw (the Kwik fuse panel uses 20 amps for the headlight switch)?
3. are fusible links better than in-line fuses?
4. is 8 gauge (30 amp capacity) sufficient for a single lead to a terminal block to feed both circuits?
5. what size wire do I need to run from the relay to the high and low beam leads (the Kwik kit uses 14 gauge implying 15 amp capacity for each circuit)?
6. should I fuse the single lead to the terminal block, or fuse the two individual leads from the terminal block to the relays?
7. should I forget the terminal block and just run two smaller wires from the battery connection at the starter to the relays.

Anybody willing to just lay out the design I should be using -- wires, fuses, etc. from point to point?

Thanks,

John

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Old 07-13-2005, 04:49 AM
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I could go into a lengthly explanation,but it is much easier to point you to the below web site.

http://www.madelectrical.com/electri...adlights.shtml

Vince
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Old 07-13-2005, 06:00 AM
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Vince,

The madelectrical link is where I learned of the need for the relays. But it didn't provide enough specific information on wire sizes and fuses/fusible links.

It did say that an 8 gauge wire was run from the alternator to the horn relay bus bar. I don't have an available bus bar in the engine compartment that I am aware of.

I think I understand the concepts, just don't know what size wires/fuses to use.

John
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Old 07-13-2005, 07:51 AM
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This is how I did my Camaro:



I ran a heavy gauge (like 6 ga.) from the alternator to a Bussmann #15600-06-20 fuse block (Click here for a picture of the catalog). Then I ran two separate relays, one for high and one for low. The original power wires were then used to activate the relays. I did some research and could never find amp ratings for lights, so I popped in 30 amp fuses. The Madelectrical site uses fusible links. This has worked fine for me, but I cannot say if the fuse sizes are correct.

I also run power for my electric fans from this block. This change has greatly increased the performance of my lights as well as created less strain on the charging system.

I found the fuse block for like $8 at Advance Auto Parts. The relays (by Pilot) are $5 each at Pep Boys.

If you are concerned about sizing fuses, I would recommend the fusible links as delinated on the Madelectrical website. Good luck, Ed www.edgesz28.com

Last edited by edge; 07-13-2005 at 08:25 AM. Reason: Add catalog picture of Bussman Fuse Block
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Old 07-13-2005, 10:22 AM
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If you use 10 awg or 12 awg for your wires from the relay contacts to the halogen lamps you will be fine. Those wires will have to be protected by either a fusable link or fuses of the appropriate sizes. As a general rule, 12 awg needs 20amp, 10 awg needs 30amp.

Vince
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Old 07-13-2005, 01:37 PM
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Thanks Edge and Vince,

That is what I needed to know. Advance Auto had the fuse block in stock, I am on my way to get one. Exactly what I had in mind.

My project is a 1939 Olds that my wife drove in high school 35 years ago. It has been parked in her dad's garage, all original, for 30 years and is coming alive with an Olds 350 engine, OD trans, 3.42 gears, A/C, all new wiring, etc.

John
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Old 07-13-2005, 07:43 PM
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Your welcome, sounds like you have a neat project on your hands.

Vince
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