Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
Hello & Welcome,
Do you have the schematic for the horn system?
If not, would it help to have it?
I thought I would send along the schematic, just in case.
You didn't mention checking for power at the relay or the fuses shown in the schematic, so I would check those first. I would then remove the relay from the socket and check that power is making it all the way to that point.
I would also check the ground signal is making it to the socket when the horn switches are pressed. If some of these signals are not making it, then you will have an idea of what wires to chase down.
I assume you know what the horn relay is, but just in case, I have included a diagram.
I hope this helps. Please let me know what you find or if you need more information.
Take Care, Greg A.
What I would do is either try to back-probe where the black wire comes into the relay socket, or just remove the relay and carefully put a test probe into the socket pin where the black wire connects. Then I would press the horn button and see if the signal switches (or connects) to ground. That means that you will have to use a multimeter set to the Ohms scale. One probe will be in the socket, the other will be connected to a good frame ground.
Unfortunately I do not have a diagram of the relay socket and can't tell you exactly what pin is that ground. But if you can see the wiring coming to the socket, you should be able to figure it out based on the wire colors.
I hope this helps. Please let me know what you find.
Sounds good. I will wait to hear what you find.
From what I can see, circuit 1902 is the one coming from the "LCD Fuse" (5 amp), which should be in the main relay block. Did you check that fuse, and that power was making it to the Red wire (with the black tracer) at the relay?
What was the CCM test that you did?
I would think that if the CCM was working, the Horn would sound of the alarm was set off or if you have a remote that causes the horn to "chirp" when the doors are locked.
Do you have such a remote and does the horn make a noise when you lock the doors?
Just make sure that both power sources are making it to the relay - the one from the LCD fuse allows the relay to turn on if the horn button is pressed (or the CCM turns on), and the one from the Theft fuse (orange wire) that supplies power to the horn when the relay closes.
If those are both making it to the relay, and the relay works, then we will have to trace it back to the controls. You should also be able to test that the wiring from the relay to the horns is OK by jumpering briefly from the Orange wire at that relay socket (pin 1 on the schematic) to the Dark Green wire (Pin 4 on the schematic).
Please let me know what you find.
Take Care, Greg A.
If you have power on the Orange wire and jumping to the Dark Green wire did nothing, then you have a problem with the wiring to the horns because you said you tested the horns by applying power directly to them.
Let me see if I can find the location of that C100 connector which is shown in the schematic. That would be the next logical place to look.
Thanks, XXXXX XXXXX
I did not find a diagram, but the description of the C100 connector is: On the Left-Hand side of the bulkhead (dashpanel). The schematic shows pin G5 as the connection point.
I believe that is correct.
If you have to, you should be able to follow the wire out of the relay back to the connector.
If you have found pin G5 of the C100 connector, is should have Dark Green wires on both sides. I would put a jumper in the relay socket that connects the Orange wire (power) to the Dark Green wire of the relay socket. Then use a test light or multimeter to measure for power at the C100 connector - on both sides. You should have power at those points. That should then lead to the horns. If the horns are OK, and they have a good connection to ground, they shoud work.
I hear you about having more space to work in!
Can you verify that you have power at the Orange wire connector (at the relay socket)?
If so, then you are correct about the horn sounding when you jumper (or cross) the Orange and Dark Green wire.
As a test, if you use a test lead and apply power (12 volts) directly to the Dark Green wire at pin G5 of the C100 connector, the horns should sound. Be careful not to touch any of the other pins!
If horns sound, the wire between the relay and the C100 connector is OPEN (broken) and will need to be replaced.
Not a problem.
What we are trying to do here is apply power (12 volts) directly to the G5 pin of the C100. So all you will need is one wire, almost any wire, to attached between 12 volts and that pin. What I would suggest is a relatively long thin wire that will reach from the positive battery post, or even that orange wire in the horn relay socket, to the G5 pin. Any source of 12 volts in the vehicle will work.
Then just connect to the 12 volt source, and at the other end of this wire, carefully touch it to the G5 pin. Of course each end of the wire will have to have the insulation removed to be able to make contact.
Does that help?
Hmm. That sounds odd, because you said you found nothing at that G5 pin on the previous test. During that test, you were to have a jumper wire between the Orange wire and the Dark Green wire at the horn relay socket. And that wire should have had 12 volts on it (as measured with a meter or using a test light).
What that the case? Did you have 12 volts at the dark green wire of the horn relay?
OK - give me a minute so I can draw up a little "test chart" on the schematic. We will be looking for voltage a various points starting from the fuse to the C100 connector.
OK - Here is the diagram.
I have numbered the steps and you should do them in sequence (1-4).
1 - Measure for 12 volts at the Orange wire of the Horn relay.
2 - Place jumper between the Orange wire and Dark Green wire of the Horn relay (this can be done directly at the wires or in the sockets of the relay - whatever is easier. Leave the jumper in place.
3 - Measure for 12 volts at the Dark Green wire of the horn relay (just verifying that it makes it).
4 - measure for 12 volts at both sides of the C100 connector.
All of the measurement can be made with a test light or multimeter, with one test lead connected to a good ground, and the test lead used to probe each test point.
What we are trying to do is trace the power along the "path" that it should take and see where it is getting lost.
Please let me know if this makes sense, and let me know what you find.
I should be here.
I am starting to think that the socket for the horn relay may be bad. That is - if you can not use a jumper to get the power from one side of the socket to the other, then there might be a problem with the connections from the wires to the socket itself.
It sure seems strange, at least for a part that is not too close to the battery. I have seen corrosion from the battery get into contacts and mess things up in the past.
I will see if I can get more details on that C100 connector, but so far I haven't had much luck finding more. Information fron vehicles more than about 10-15 years old can be hard to come by. You may have been documents than I do at this point.
I will let you rest your bones for this evening. Let me know when you are ready to start up again - just send me a note.
I would have used a big jumper wire in the sockets for the orange & green wire.
Then I would use just one probe (the positive probe) from the tester, to touch each wire. The other end of the tester should almost always be connected to a good ground point on the frame. That would be a shinny metal point somewhere.
There you go - Good attitude!
Have a good night, Greg A.
These connectors will often have a screw or bolt in the center to keep them secure.
But since I can not find a detailed diagram, I am not sure about this one. Perhaps you have better diagrams than I do.
Without being able to see what you have there, and very little to refer to here, I am kind of stuck too.
I will continue to see if I can find some diagrams with more details.
Thanks for you patience.
You must be reading my mind - a photo (or two) would be good.
If you need instructions on how to upload any pictures, just let me know.
OK - First part is to get the pictures onto your computer. I would suggest a separate folder if you can make one.
One other thing - there is a limit of about 0.5 megabytes for each picture, so you may have to resize them. Not sure if you will have to do that or not.
Anyway, once you have the pictures on your computer, come back here and if you see a line in the reply box that says "Show Toolbar" then click on that so that you can see all the other tools available. Once you see the toolbar, there is an icon that looks like a little tree. You will click on that to upload the pictures - one at a time. When you click the icon, a "requestor" window will pop up that has a "Browse" button in it - click that button and then another pop up will show up with another Browse button. Click that button and then you can find the folder and files on your computer to upload. Once you select the file, there will be buttons to say "OK" or "Insert". Just keep clicking until you make it back to the editing screen.
It may take a couple of seconds, but if it all works, you will see your picture in the screen.
Give it a try and let's see what happens.
Here is what you may see:
Or if you have the toolbar on already:
Once you have the second one, here is the icon you will click:
I assume you mean Internet Explorer (IE).
Can you select the "About Internet Explorer" item (as shown below) a let me know what you see?
Here is what mine says (IE 7):
I have not upgraded to IE 8 yet. I am a bit over protective when upgrading MS stuff - I like to wait until all the bugs are worked out. Plus, my son, who works in the IT industry, just had a nasty experience with IE 8. He said something about the upgrade changed a bunch of drivers that is shouldn't have changed. Even stuff that had to do with video and sound drivers was not working after that upgrade.
Let me know if you hear from customer service.
I will also send them a note and see what I can find out.
It sure look pretty tight in there.
Is there enough space to try and "unwrap" some of the tape on that wiring?
Here is a smaller version of one of your pictures.
Assuming that you have some electrical tape to wrap it back up, it might be good to unwrap a few inches to see if you can locate that wire.
As a reminder, we would be looking for a couple of dark green wires going to pin G5 on that connector.
Once that is found ( and confirmed), you will want to see if there is power at that point when that jumper is installed at the horn relay.
I also forgot to ask: Does it look like there is any corrosion on any of the wires at that connector? I can't really tell from the picture.
I would say - go for the dinner!
For jumping the relay, this is where I wanted you to put a jumper wire in the horn relay socket so that power would come through there all the time.
But for now, let me know if you can find the right color wire and if it looks like it is in the right place (G5 should be 5 pins from one of the sides).
Let me know what you find after you eat and get back to this.
That sounds good. The fact that you have two dark green wires is a good thing because there should be two wires - one to each horn.
Now, what we would like to do is see if there is power making it to those two wires when you either press the horn button, or put a jumper wire in the socket pins of the horn relay.
You could also try to CAREFULLY apply battery power (+12 volts) to the connector of those two dark green wires. If all the wiring to the horns is good, the horns should sound when you do that.
If that works, then you would have to check the connections to that same pin on the other side of the firewall (sorry about that).
I am starting to think that it would be easier to get back to the moon than to get this thing working again - lol. Or maybe just rewire from the relay to the horns.
Hurray for the Good News!
On the other side of the firewall, there should be the same type wiring harness coming into the other side of the connector, but it would be "rotated" 180 degrees from the other side (I hope I said that right). That is where the wire from the Horn Relay output pin should be connected.
Let's hold off on the rewire thing for now, but if we get to that point, you would have to put a wire from the horn relay to that connection you touched to make the horns sound.
So now it is time to going back to the horn relay and check that output. There should be another dark green wire going from there to the G5 pin in the C100 connector. As a quick test, you could apply power to the horn relay pin (like you just did) and see if the horns sound. That way you will not have to look for the inside connector to test it.
Please let me know what happens.
Yes, that would be my next step. You might just want to apply battery power to it, when you find it, to make sure it is making contact through the firewall connector.
If you have an ohmmeter, you could check back at the dark green wire at the horn relay and see if you have a good connection all the way from one of the horn wires back to that point. You would have to do this by "extending" one of your test leads from the meter so it would reach from the outside to the inside, but then you wouldn't have to hunt for that C100 wire on the inside of the firewall.
Thanks for all your patience in this process.
Next would be to put 12 volts on the dark green wire at the Horn Relay connector. We are just moving our way backward - so to speak.
Sometimes the relays themselves have little diagrams on the side or bottom of them. What we are looking for is one of the relay contacts - NOT the coil. One side if the contact will be power (the orange wire) and the other side will be the output contact (the green wire).
Also, I don't know about you, but sometimes the colors can be hard to see (for me) when there are dark tight spaces. You should have at least 4 wires at the back of that relay - Orange, Dark Green, Red/Black (black tracer) and Black.
Also, I was checking out one of the forums here and ran across a note about IE 8 not showing the toolbars. Here is what it said:
I had to use the compatibility tool at the top near the address bar it was ok after that.
Since I don't use IE 8, I am not sure what they are referring to, but if you want to take some more pictures (of the horn relay area) and try to upload them here, then you might want to try and do that. Otherwise, maybe we could send some more pictures through customer service again.
OK - it sounds like it has been a pretty full day, but at least we know the wiring through the firewall is OK.
If you get a chance to try out the picture thing, send me a picture of the car, as a test.
One other trick. We might want to use the process of elimination to figure out which socket pins is for what. Two should have power on them - the orange & the Red/Black. By pulling out the "Theft" and "LCD" fuses (on at a time), you should be able to figure out which is which. That should only leave 2 other sockets to pick from.
Get Some Rest, and we can start up again in the AM.
P.S. I am on Pacific time and my wife has "plans" for us tomorrow afternoon.
Here is a photo taken with my cell phone. This at least works now. According to the message I am now "backward" compatible, seems like it is the other way around!!!
Hey - It worked!
Kind of a small picture, but it looks like a sweet ride!
Thanks, XXXXX XXXXX raining tonight, but hopefully I will have it back together for the weekend!!!
Good morning Greg
Here are the results of my testing on the Horn Relay:
1. Leftmost cavity "dead" all of the time
2. Top Center cavity blows horn when 12 volts input with either Theft or LCD fuse pulled, i.e. not controlled by either fuse
3. Rightmost cavity is hot and is controlled by LCD fuse
4. Bottom cavity is hot and is controlled by Theft fuse
Hope this helps with our next step.
Am looking into pulling some of front panel off to see if I can see the wires, but maybe the test will give you what we need..
Panel removal will require removing complete top panel of the dash as far as I can tell. Pulled some parts off and can hardly see behind relay panel. Hope we can find some other way to resolve.
Is there any way you can get a picture of the area of the horn relay & socket? I am just thinking that it might help me a little (or maybe I haven't had enough coffee yet)?
Also, in item 2 above, you said "Top Center blows horn when 12 volts input" - Does that mean the horn sounds when 12 volts is applied to that pin?
Good morning, Greg
A picture of what is exposed will show nothing, no wires etc. are visible. All I can really look at are the relay plugs and receptacles.
Yes, the horn does sound when 12 volts is applied to that pin.
.Hope that helps
The relay plugs and receptacle would be fine. I am just trying to get a picture of it in my mind.
The fact that the horn sounds when you apply power to that pin is a good thing. That probably means that the wiring to the horns is OK, and the issue is on the "input side" of the relay.
I sent some photos, but could not enter text with them. Not sure if photos came out as they were quite large on my reply screen.
Please, Let me know
I see the pictures. Let me take a look and see what we can do.
OK - I have a HUGH favor to ask.
Can you get a picture of the empty socket and the "pin side" of the relay?
I suspect the relay looks something like this - correct?
Sorry for delay, my system did not alert me or maybe i just did not hear it.
Here is picture of socket and relay, except for color your picture is identical to mine.
Sorry for the delay too, pretty busy around here today and I have to be running off in a little while.
Unfortunately, it looks like those pictures were out of focus.
The one I really want is the blank socket, but perhaps I don't need it. You said that one of the socket pins was "dead" all of the time. I believe that particular pin it the "input" signal from the horn switch and the CCM.
What I would like to try, as an experiment, is to see if you can put a thing wire into that socket, and then put the relay in too. I guess the wire should be several inches long and the insulation should be stripped at each end.
The "experiment" is to try and see if you can touch that wire to a good ground and make the horn sound. This would be like putting in your own horn switch, and is just to see if the regular horn switch circuit is the problem. This has to be done with relay in place, and both of those fuses too.
If you can see and reach the Black wire at Pin 2 (on the schematic), then that would be the same circuit and you could just try grounding that point.
Did I explain that well enough? All we are doing is moving back to the input side of that relay now to see if it will work by grounding the input pin.
Pictures are out of focus due to lack of room to get camera into area. Sorry, I tried.
I will try putting wire into circuit tat seems to be dead. Thanks
If you can get the horns to sound by connecting that point to ground, then we will be looking at the horn switch circuit (the switch itself or the Ground feed to it).
Just to let you know, I will be taking off to attend a family function, but should be back later this afternoon or early evening (pacific time).
Good news, I think, the horn sounded!!!
I will be leaving this afternoon also, be back later tonight. Please leave me a post and we can go from there.
Just musing while waiting for my wife to get ready to go out.
The socket we used was supposedly dead, i.e. it had no power and it would not work when we applied power to it from the Orange wire/circuit. Now we plug in the relay, ground it and suddenly it has power to blow the horn.
Electricity is something I have never really understood and this just adds to my confusion. I am sure there is good reason, but it sure is beyond me!!!
Thanks for "listening,"
I have some time before having to leave too - wife is not here yet & we are riding together.
I think of electricity as "water" and the wiring, relay, etc. as the "plumbing" for a system. If the pipes break, or a valve doesn't open or close when it should, then you have problems. The hard part is identifying the right parts and know what to look for. That is basically what we have been doing so far.
I think that socket pin that was "dead" is the input signal from the horn switch (button). When the horn button is pressed, that pin should be connected to Ground, through the switch and connected at G201 (from the schematic). I also noticed that is a "splice" between the Ground point (G201) and the connector going to the horn switch (C204). C204 might be the next point to find to see if Pin D is connected to G201 (probably is) and that Pin G is switched to ground when the horn button is pressed. If you have a good connection to ground at Pin D and Pin G does NOT switch to ground when the horn button is pressed, then there is a problem between that point and the horn buttons.
Unfortunately, I do not have diagrams for where these connections are, but I do have descriptions.
C204 - Below Instrument Panel, Right-Hand side of the steering column
G201 - Below Left-Hand side of Instrument Panel, on the Left-Hand Kick Panel
S203 - Instrument Panel Harness, Lower Left-Hand side if instrument panel, Left of Steering Column
If you can find the C204 connector, then see if you can check out Pin G and touch it to a good ground (like before).
If you have an ohmmeter, also check that Pin D is connected to ground.
If all of that is good, and the horn does not sound when you press the button, we have found the problem area (probably the horn switch or wiring to it - from C204 and up through the column).
Please let me know when you get a chance to test this out and what you find.
P.S. Wife is home now & I will be gone in a few minutes.
Just got home myself (9:30 PDT).
Let me know what you find tomorrow.
What is the model number of that multimeter?
Does is have an Ohms setting (may look like this Ω )?
Yes - I meant pin D.
Well I think we have all we need to know. Sounds like the switches or wiring going up to and back from the horn switches is bad.
From what minor instructions I have, I can not tell if the horn buttons can be replaced without replacing the air bag module. But to get in there and test the wiring, the air bag module will at least have to be removed. Sorry about that.
I think you have already tested the circuit as much as you can without getting into the steering column. You might be able to gently pull & push on the other end of the C204 connector wires (the ones that go up the steering column) and see if that has any effect.
Here are the instructions I have for replacing the horn switches. They say to remove the air bag too (not too encouraging).
I don't suppose you would want to wire in a separate horn button? Probably not. It would function, but probably not look very good. Wouldn't do much for resale value either.
I think you are right - we have gone about as far as we can at this point without getting into the column. If you have club friends, they may have to tools. Some parts stores also have "loaner" programs for tools. Usually there is a small deposit that you get back when the tools come back.
As for the fee, you have set it when you started the question, but there is a "bonus" that is available if you decide to accept. You can be the judge. If you want to use that, that is fine. You can set the amount there too, I believe.
If you want to get me again in the future, just put my Username in the subject line of any questions. If I see it I will check it out, or one of the other experts sees it, then they should send me a note to let me know you are looking for me (that is what I do when I see questions for other experts).
Sorry we couldn't go much further, but if you do get it apart and fixed, please let me know what it ends up being. Oh yeah - how about sending me a close-up picture of the bad part?
Take Care & Good Luck, Greg A.
You are quite welcome & it was great working with you. Thanks for the accept, bonus, and kind words.
I look forward to us working together again in the future.