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Lighting Forum
Angel Eyes, DDEs, lighted rings, Clear Turn Signals, LEDs, Xenon, HID, or Bi-Xenon. If it lights up and you want to discuss it, post here!

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Old 10-21-2006, 04:50 PM   #1
cowmoo32
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Quick Question about wiring

I picked up some FIAMM horns. I need 12v power going to the air compressor. I've already got DDEs wired up, can I just tap into the positive lead from the DDE relay?
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Old 10-21-2006, 05:17 PM   #2
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Air compressors tend to blow low power relays and fuses.

If you are planning on replacing your oem horn, I would suggest running a new relay switched by the positive lead going to the stock horn. This will only power the relay's switch. The actual power being switched by the new relay should come from a fused source with a higher amp rating.

My previous vehicle was an Isuzu Trooper. I used it as a first response vehicle when I was an EMT. I used a similar air horn setup (with separate compressor) wired as described above. I ran a dedicated power source with an inline 20 amp fuse (I think) to the switched leg of a 40 amp auto relay, then out to the compressor. It worked very well.

If you are running a separate switch, I still recommend using a dedicated power source and a relay.

If the air horn came as a kit with switching and relay(s), follow its directions as to where to tap into (in terms of amp ratings). The relay switching can be done with a very low amp rated supply (like from the DDE), but the power that runs the compressor should be from a high rated supply. You run the risk of damaging the DDE ballast, or blowing that fuse by overloading it with the draw of the compressor.

Hope that isn't too confusing - I'm much better at doing the installation than explaining it clearly.
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