72 Cutlass horn not working.

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Old Aug 28, 2017 | 07:41 AM
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budg's Avatar
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72 Cutlass horn not working.

This weekend noticed the horn wasn't working , so I started to delve into it. I have an aftermarket steering wheel so I suspected the horn mechanism. Took center cap off. Checked voltage at black wire to ground , I got 12 volts and when I touched the wire to ground relay clicked. Next off to horn relay. With horn energized I pull the green wire off the relay and checked its output to ground . 12 volts, so it appears that is ok. According to the diagram it appears the green wire goes to the horns , so my next step is to ring out the wire from the relay to the horns . If I have continuity , then look for a bad ground or a bad connection.

Is there anything else I should be looking at? One thing of note is the relay has a 3/8 screw that holds it to the firewall. That screw was lose allowing the relay to move a bit. I tightened it up. Does this screw ground the relay to the chassis? The screw was a bit corroded and the relay looks like original equipment. Appreciate your thoughts.
Old Aug 28, 2017 | 08:12 AM
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Yes it grounds the relay. If you touch the green wire to a 12v source then the horns should blow. If they don't disconnect the wire at the horns and see if you have 12v there. If you do then you possibly have bad horns or bad grounds.
Old Aug 28, 2017 | 08:56 AM
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Thanks oldcutlass. Thats what I thought. I will make up a jumper wire to run back to the battery and test the horns and the green wire. If I get the horns to blow by running 12 volts thru it then I know the horns and wire are ok and need to look at the grounding of the relay.
Old Aug 28, 2017 | 09:04 AM
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You already said you have 12v at the relay output when energized, so the relay is good doing what its supposed to.
Old Aug 28, 2017 | 09:21 AM
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Originally Posted by oldcutlass
You already said you have 12v at the relay output when energized, so the relay is good doing what its supposed to.
Correct. I dont know yet that I have 12 volts at the horns. According to the schematic it appears there is be a connector between the green wire on the relay and the horns. I`ll check for 12 volts at the horn and the test the horns like you said.
Old Aug 28, 2017 | 10:55 AM
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Just pull the green wire off the relay and apply +12V to it. If the horns work, that part is fine. If not, try applying +12V directly to each horn. This is not a complicated circuit.
Old Aug 28, 2017 | 01:33 PM
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So I pulled the green wire from the relay and put 12 volts to it . The horns blew, so I know that part is fine . I plugged the green wire back in and pulled the wire to the horns and got nothing. I rung out the green wire between the relay and the horn (disconnected of course). I got 0 ohms which means its ok. Double checked my voltage at the terminal, yep 12 vdc. Plugged it in ( I even put a new connector on the green wire). Had the wife pushed the horn down and jiggled the green wire while it was on the relay and the horn started working.

Apparently the terminal where the green wire plugs in is lose. It probably happened when the screw losened up and the relay was moving around. So its a new horn relay for me. Appreciate the help oldcutlass.
Old Aug 28, 2017 | 01:46 PM
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It may be just the green wire terminal on the relay had some corrosion. Clean everything up, tighten the mounting screw, and see if it all works again.
Old Aug 28, 2017 | 03:54 PM
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Oldcutlass, thanks for your help. After cleaning the terminal and putting a new terminal end on it still doesnt blow the horn unless I move the wire. It appears the terminal post on the relay is lose and if I move it just right the horn blows. I am going to replace the relay . This one looks to be in rough shape anyways.
Old Aug 28, 2017 | 07:01 PM
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Probably a good idea, glad you were able to work through it.
Old Aug 31, 2017 | 01:57 PM
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Ordered my horn relay from amazon and installed it . Horn works great . It appears the contacts were burnt as was the coil. Thanks for all your help.
Old Aug 31, 2017 | 02:39 PM
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Well done, time for a trip for ice cream.
Old Aug 31, 2017 | 03:29 PM
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Ha , true enough.
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