Recently, my right side (passenger) horn stopped working. It seems to be the low tone as the horn that sounds is pretty high.

-If I disconnect the horn from the electrical connector and wire it directly to the battery, it sounds which means the horn itself is good.
-Because the other horn (left/driver side) works and sounds when I push the steering wheel, that means the switch/relay/fuse are all fine (right?)
-I hooked up a test light onto the positive terminal of the electrical plug and the other side to the negative terminal of the battery - with the key in, and when I press the steering wheel to honk the horn the test light illuminates - this means its getting the 12v it needs.

Based on the facts above, I believe the cause of the horn not working is a bad ground. I took the battery tray out and followed the electrical wire down. However it's hard to tell what is going on down there, the wire splits into a Y and I cant tell where the ground for this horn wire is. It is also difficult because the 4x4 vacuum actuator is right in the way. There are a few eylet/bolt grounds on the radiator support but I cant tell which one is for the horn - all of these look very rusted and don't want to touch any I don't have to.

Does anyone know offhand which one belongs to the horn, or is there a different creative way to ground the horn?

It started raining so I had to put everything back together fast and didn't get a picture - I will try to post one tonight after work.

Thank you in advanced.

 

Just because the light glows does not mean it's getting 12 volts, check with a meter - with all grounds if rusty - corroded Ect. clean, repair, replace as needed

 

I need the year of your truck to tell you where the ground is.

I agree, use a multimeter .

George

 

Sorry forgot to mention...2000 Blazer ZR2 - I can post a picture later tonight of what it looks like under the battery tray.

 

horn connector is the connector closest to the camera

 

The ground for the right horn goes through splice SP101 being joined with the right fog lamp and right park/turn lamp grounds and then grounds to the frame at G109 near the right radiator support. If the other two circuits are affected then its the ground. If only the horn then its from the splice back to the horn.

George

 

When I press the horn button in the cab, the right turn indicator on the instrument panel lights up so it makes sense these are related. Is there a diagram of grounds? how do I find g109? thanks again this has been very helpful

 

The fact that energizing the horn makes other lights come on means that this is not a ground problem or at least there is more than a ground problem. All three circuits that you are talking about share the C4 connector at the under hood fuse block at the top of the left front fender. My money is on a corroded c4 connector or corroded wiring in the vicinity of that connector. Look for water damage, green corrosion, powdery dust, frayed wiring, etc. If it’s not there, follow the wiring harness away from the fuse block as far as you can and look for damage.

does this truck have an aftermarket security system? If so it may be tied into all of those lamps and faulty, if my primary theory is wrong.

Report back.

George


George

 

The first picture is of an electro siren next to the fuse box - is this aftermarket? the ground was clipped/broken as you can see in the picture. I grounded this and it made no difference with the horn.


I couldn't really find connector c4, I guess i'm not sure what i'm looking for - I took a picture of some white dust looking stuff - is this the corrosion you were talking about? What does C4 look like and where do I look for it?


Then just to see what would happen, I put a paper clip on the positive terminal of the electrical connector that plugs into the horn and jumped it to the positive terminal of the horn. Then I jumped the negative terminal of the horn straight to the negative terminal of the battery - the horn sounded when I pushed the steering wheel, but with the keys in ignition before starting, the right turn signal indicator is on as well as my front parking light is out when the horn is hooked up this way.

 

There are a number of issues here so let’s back up and do first things first.

the horn relay and fuse are supposed to be power by “always on power” meaning that you don’t have to turn on the ignition to the run position to sound the horn as you have indicated. Leave the ignition off. Pull the horn relay and see if you have power to pins 1 and 5. Then replace the relay, activate the horn and see if you haVe power to the horn fuse. If there is no power at those locations, turn the ignition on and repeat. If you have to turn on the ignition to activate the horn then there’s is a significant change in the power circuit that is not factory original.

pull the connector at the right horn and use a multimeter to measure the resistance of the ground pin on the connector to the battery ground. Repeat this with the left horn and compare the results if the right horn ground resistance is significantly higher then you do have a right horn ground problem. Follow that wire to the ground point that I described in a previous post to find the corrosion, break, or loose connection.

you appear to have an aftermarket security system. Get under the dash and find the brain box and follow all of the wires to see how “custom” the install is. The malfunctions can all be influenced by this install.

are you saying that the dash indicator for right turn signal turns on with horn activation but not the actual right turn signal bulb? If so, does that bulb work normally?

does the front right parking light operate normally otherwise? Does it go out when you attempt normal horn activation or only with the Paperclip experiment?

yes that powdery dust is usually electrical corrosion or acid. Any shorting due to corrosion might be at a spot like that. If that’s a wire wrap, peel it back and see what you’ve got. My original suggestion about a common connector is probably under the fuse box. Let’s not start pulling that up until these other things get straightened out.

George