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MG MGB Technical - horn relay

I want to take a set of 2 terminal horns to a loader set of one terminal horns. The way it is wired now it that the hoens always have 12 volts on them, and when the horn button is pressed it completes a ground and the circuit. Is there a relay I can buy at any parts store that has spade connectors, the would close the circuit in the same way and result in turning on 12 V to a single wire? Cheap is always better
Frank Baker

Yes, auto parts stores sell generic relays for less than $10-.
Kimberly

Frank - Any parts store or Radio Shack should have the little Bosh style relays in either a single pole, single throw (SPST) or single pole, double throw (SPDT) configuration, with contacts rated at 30 or 40 amps. You need the SPST type, although either configuration will work and as Kimberly stated, they should be less than $10. Cheers - Dave
David DuBois

This is exactly the circuit my Maseratis have. 12v goes to the top of the coil and one side of the contacts. When you ground other end of the coil via the horn push the 12 v is switched across the contacts and spins up the compressor where the circuit is closed by an internal gound. So a 2 terminal coil relay and a single make floating contact will do it, you could even have one side of the contact common with the 12 v end of the coil and still do it.
Stan Best

Thanks - On my way to the auto parts store
Frank Baker

Excellent - it works and now I have a big car sound when some SUV does not see me. Thanks.
Frank Baker

Me not very good with car electrics! Is there any chance one of you clever clogs [I mean that in a complimentary sense :-)] can knock up an image like this for the "12V For Dummies" members of the circuit you used?
http://www.bestimageupload.com/files/ytzmzdnn4myx0gu2zgyz.jpg
Paul Morgan

Paul, try here:

http://www.mgb-stuff.org.uk/horns.htm#2wire
...

Yep. That will do nicely. Thanks - Monkey see monkey do!
Paul Morgan

All I did was this

- I went to the junk yard and to the full size chevy area. I looked at horns until I found a set with spade connections. One bold and a little money later – I had the horns (2, one high, one low)
- I purchased a 30 AMP 4 pronged relay from PepBoys ($5)
- I wired one side on the relay with the orginal wiring from the horn – On – off, where on is grounded through the horn
- I crimped a jumper from the positive side switch to the higher amp side
- I used existing wire to take the power side to the horns that ground to the body now
- I taped the extra feedline down and that was it.
Frank Baker

This thread was discussed between 05/02/2007 and 15/02/2007

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