How to troubleshoot dead horn.

WILBER100

MEMBER
2007 GMC SIERRA
36,000 MILES

My 2007 Sierra Cassic WT horn died. Started out as an intermittent problem, occassionaly it would be a weak sound, then ultimately stopped completely. The horn relay was verified good by the fact that I can hear it actuate and that I pulled the 15A horn fuse in the underhood fuse block and measured the B+ voltage coming on and off when the horn switch is pushed. This only leaves the path from the other side of the fuse through the connector on the bottom of the fuse block then to the horns then path to ground. I took my best guess on the pin on the connector under the fuse block and jumped 12V to it, and still nothing. The horns are EXTREMELY hard to get to, so I can't jump 12V directly to the horns. Since both horns are dead and they each have independant gound paths, I think the problem is between the fuse block and horn, but I still can't nail it down. Thanks for any help.

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3 Replies

SATURNTECH9

MECHANIC
30,869 POSTS

What I would do is find the dark green wire that comes out of the fuse box that splits into to feeds. With the horn pushed and fuse in make sure both wires have a feed only when pushing the horn button.I know you jumpered power to the wire but this will sure you have the correct wires and there is power going thru them. If thats good you will have to make sure there is power at the horns and both horns have a good ground of 2 ohms or less to ground. Its easier to make sure the power is coming out of both wires from the fuse box and that its not making it to the horns or the grounds are messed up. Then tracing the power feeds to the horns because you assumed that was the problem and it wasnt.I learned to never assume anything when tracing down a electricial problem.

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Saturday, July 21st, 2012 AT 5:02 PM

WILBER100

MEMBER
7 POSTS

OK thanks saturntech9. If I can get to the crazy thing, I'll do that. I just can't believe how impossible these horns are to get to. It looks like I may hae to take the grill and fenderwell of to get the headlight out to get to the horn! What the heck?

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Saturday, July 21st, 2012 AT 9:13 PM

SATURNTECH9