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85 r80rt single horn to duo horn

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John Young
Posts: 45
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I am converting my single horn to a Fram duo horn setup on my 1985 r80rt. I will use a relay and it will be powered thru my Eastern Beaver PC8 fuse block. I have searched for a drawing showing how to wire this thru the relay with no luck. I have a four pin relay and want to make my own harness. I am limited on my electrical knowledge but if anyone has a simple drawing showing which wires go to which pin on the relay I would appreciate the help. 85, 86, 87 and 30 are the pins. Which pin do I tie the original horn wires to and which pin does the duo positive horn wires go to? 30 should go to battery positive with an online fuse. Signed, Dazed and Confused.

 John Young

Posted : 06/02/2023 00:06
Richard W
Posts: 2529

There should already be a "horn relay" in the layout of the OEM R80 harness. If you can locate that, then all you need to do is disconnect the OEM horn and connect your horn in its place. 

If there is no horn relay in your harness, then the 2 wires to your existing horn will be used to power the coil inside the new Horn Relay. The new horn will be connected across the "normally open" (NO) contacts on the relay like this:

• One of the NO relay contacts will go to one of the contacts on the horn.

• The remaining NO relay contacts will be connected, with a fuse, directly to the Positive on the battery, or the RED wire within the harness.

• The remaining horn contact will circuit back to any "ground" point within the harness, or on the frame, or back to battery Negative.

In this way the horn button energizes the horn relay's coil. The horn relay's NO contact set will close on command from the coil, thereby creating a closed circuit to the horn. At which point the horn will operate. Draw it out on paper for yourself. It's a very simple circuit that's more easily understood with a line diagram.

Hope this helps.

This post was modified 10 months ago by Richard W

Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.

Posted : 06/11/2023 09:26


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