relay for a triggered horn

Hello, I have a horn with a negative trigger wire and an alarm with a negative horn output. I'm trying to wire up a 775 to them both but i'm not sure what wires go to what pins. could someone please help? Thanks

The alarm's horn output will need a rely, it's neg output won't be enough to ground the horn (about 7.5amps) to make it work unless you're referring to a factory horn and the input is before a horn relay. What's a 775? Also what vehicle?

Thanks for your reply:

howie ll wrote: The alarm's horn output will need a rely, it's neg output won't be enough to ground the horn (about 7.5amps) to make it work unless you're referring to a factory horn and the input is before a horn relay. What's a 775? Also what vehicle?

I am using the factory horn and I'm getting the horn output from a GREEN/ YELLOW wire on the steering column. a 775 is a universal relay, If I'm not mistaken. My car model is 2006 pontiac vibe. https://www.the12volt.com/installbay/forum_posts.asp~TID~33385 Thanks

Try a direct feed from the alarm's neg if not, as follows: alarm output to 85, 12v+ constant fused 2-3amps to 86, good ground to 87, 30 to horn input. Diode, 1N4004 across 85 and 86, diode band to 86. Method "B" cut the horn wire, using a DMM set to at least 1+ amps range, Black probe to steering wheel, red to horn, sound the horn. If the draw is 120ma or less, the direct - output from the alarm is sufficient although the relay is safer. By the way in practical terms, there ain't no such thing as a universal relay.

howie ll wrote: Try a direct feed from the alarm's neg

Interesting, my manual shows a diagram with a relay between the alarm brain and the horn. u think if i just connected it directly that it might damage the brain?

howie ll wrote: if not, as follows: alarm output to 85, 12v+ constant fused 2-3amps to 86, good ground to 87, 30 to horn input. Diode, 1N4004 across 85 and 86, diode band to 86. Method "B" cut the horn wire, using a DMM set to at least 1+ amps range, Black probe to steering wheel, red to horn, sound the horn. If the draw is 120ma or less, the direct - output from the alarm is sufficient although the relay is safer. By the way in practical terms, there ain't no such thing as a universal relay.

I'll have to build that. i don't think i could get a probe to the horn wire while connected to the button, I don't have enough wire left over. Probably would just be easier t go with the relay, but thanks for the suggestion. Oh, and I pretty much expected a correction when it came to the "universal" relay thing :) Thanks, I'll try this when the sun comes up.

Forget the 755, it's a latching relay probably hasn't got enough power handling any way. Use a Bosch/Tyco/Panasonic etc.etc. 4 or 5 pin automotive relay as suggested above. It makes no difference if you use a 4 or 5 pin relay, with a 5 pin, you simply don't use pin 87a. Also far cheaper than a 755.

reading your reply, i just realized i didn't ask something, Isn't possible to simply tap the horn wire and use it to trigger the horn? i didn't realize that i'd have to use the relay to actually come between the horn and the horn button.

Exactly what I said but unless you definitely know that either the horn wire triggers a relay "downline" or its current draw, you're safer with a relay, this will stop the alarm R/S from having its internal circuitry cooked.

just looked at a manual that says it does have a relay, I wish it showed the actual wiring. Oh well. I'll try again when the sun comes back out. thanks again!

THanks Howie :) didn't need a relay, there were two GREEN/ YELLOW wires. I just wish the wiring diagrams could be more specific :P