1957 Mercury Horn Relay Connections

I have a 1957 Mercury horn relay that is not marked for connections. It has three terminals. When mounted on the firewall, one terminal is on the left and two are on the right (one closer to the firewall than the other). Can anyone tell me what hooks where? Thanks.

 

one terminal goes to 12 volts, one goes to the horn ****on, and the last goes to the horn.

 

Not being a wiseguy, but I already knew that much. I need to know which one lands where.

 

Shouldn't be that hard to figure out. Use a cordless drill battery or a car battery and connect one lead to one terminal on the relay the other end to the battery. With a jumper wire from the other terminal on the battery probe the other 2 terminals on the relay and listen for a click. If you don't here one move the battery lead to the next terminal on the relay and probe again. When you get the click, one terminal is 12 volt and the other is the horn ****on. Next take a test light and hook between the 12 v and the remaining terminal and when you connect the horn ****on wire see if the light comes on. If it does thats the horn terminal. If not switch the horn ****on wire and the 12v wire on the relay and it should then be correct. I hope this makes sense, Brian.

 

I had to chuckle at this, but it's essentially correct. Without a label or schematic, your only choice is trial-and-error because different relays may have different connections.

One wire is a constant power supply (your horn normally blows without the key on). The second is the "trigger" to the horn ****on (horns are triggered by ground connections at the horn ****on) and the third (you guessed it) goes to the horn.

Mount the relay and test it with a power source. There are only 9 (three wires times three connectors) possible combinations and only one of them will work right.