Author Topic: Horn Not Working  (Read 12415 times)

Offline 74GMC

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Horn Not Working
« on: December 18, 2011, 08:40:37 PM »
Hi there, I know this topic has came up allot. I've gone through as many posts as i could to find out what was wrong with my horn but still can't remedy the problem.

I have a 74 GMC, I can hear the relay clicking when I push the horn so I figured that was the problem. I put a new relay in and it still does the same thing. Three wires into relay, Red,Green,Black. The red wire is the power correct? I tested it with a test light just before the relay and it is getting power. The black ground wire? from the relay runs back up to the connector on the column, it seems to be fine no breaks in it. However, does the green wire that runs out of the relay go to the horn? The wire at the horn (green), I tested with a test light, has no power. Could it be a assembly problem in the steering wheel itself? I've looked at diagrams of the horn assembly and can't seem to see a problem. From top to bottom my horn is assembled as follows:

1. Cap
2. plastic circular bushing with three holes in it( seats in between metal cup)
3. Metal cup
4. Spring
5. plastic ring in bottom of steering wheel that holds the spring up and acts as a spacer

Not sure what is going on here but if anybody had some ideas to help me out, would be much appreciated.

Thank, Riley
"Nothing Beats a Chev"

Offline 1980c10

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Re: Horn Not Working
« Reply #1 on: December 18, 2011, 09:25:54 PM »
When you are testing a circuit-use a process of elimination. Verify sections of the circuit. You know that you have power up to the relay so you are that far. Now check power after the relay and so on. Until you get to the horn or work easier sections 1st if you want; it doesn't really matter the order as much as the process. It helps to have a wiring diagram so that you don't miss anything and you can find them on this site.  When you find a problem question your test 1st and think "am i testing this right" and try other methods if you question them. ie you get power to the horn but it doesnt work you could try the horn right off of the battery etc.

Okay with that in mind-A few things;
You need to press the horn button when testing the circuit
In the horn circuit besides wiring you have a horn button, relay, junction block on the firewall, fuse and horn and the horn must be grounded.
I would start by checking the fuse
Next the horn and test with a test light the green wire straight to the battery for ground.   
Next test the green wire out of the relay towards the horn while pressing the horn button-making sure your ground is good.
If this doesn't solve it for you post your results here.

Hope this helps...

Offline bake74

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Re: Horn Not Working
« Reply #2 on: December 18, 2011, 09:38:16 PM »
     Welcome, I see this is your first post.  I like to start at the problem and work my way back.  1st. I would put battery power to the horn directly and make sure they work. (they do go out), then check the horn wires for power, and so on back to your horn button on the steering wheel.
     Over the years as a service manager, I have found this to be the best diagnostic way of solving a problem, you eliminate the guessing game that way.
#1: The easiest and most obvious solution to any problem is 99% of the time correct.
#2: There is no such thing as impossible, it just takes longer.
  74 k10, 77k10    Tom

Offline bd

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Re: Horn Not Working
« Reply #3 on: December 18, 2011, 10:13:46 PM »
...I can hear the relay clicking when I push the horn....
Since you hear the relay clicking when you press the horn button, there's nothing wrong in the column (the black wire from the relay connects to ground through the horn switch).  Probe the dark green wire at the relay - it should energize when you press the horn button and the relay clicks.  The dark green wire runs from the relay straight to the horn(s) through the firewall connector.  Your description suggests a connection issue at the firewall plug.  Study the wiring diagrams and identify the dark green wire where it exits the firewall connector. 
http://forum.73-87chevytrucks.com/smforum/index.php/topic,11766.0.html
If the dk grn wire tests "hot" at the relay with the horn pressed, it should test "hot" at the engine compartment side of the firewall plug, too.  If it doesn't, clean the connections through the firewall connector.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline 74GMC

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Re: Horn Not Working
« Reply #4 on: December 19, 2011, 04:13:10 PM »
Thanks for the help, I'll try testing the horn to see if it works then start with the drk green wire.

"Nothing Beats a Chev"

Offline bladerunner

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Re: Horn Not Working
« Reply #5 on: December 20, 2011, 12:10:02 PM »
For what it is worth, I had the exact same issue when I bought my truck.  Relays worked, then I checked the wiring, which checked out okay. I finally tested the horns themselves by swapping out a horn from my father-in-laws Harley and it worked, so I determined my horns were bad. Just had to replace them.
85 K10 Shortbed
94 Impala SS