mobilehippo Posted July 29, 2014 Share Posted July 29, 2014 Last year I posted something about a broken horn and now, sadly my horn is broken again. I've tested steering column where the horn buttons are for power. It's showing 12v so I know power is going from there. However, the wires that connect the horn in the front of the car, is not showing power. So I know something is faulty with the power going from steering column to horn with the wires. I checked the fuses and they all seem to be fine. What do you guys suggest I do? I'm looking at the wiring and its quite complicated. Looks like spaghetti. Please help! Thanks! Quote Link to comment Share on other sites More sharing options...
Alvin Posted July 29, 2014 Share Posted July 29, 2014 Fred Flinstone used a large toucan bird horn mounted on the drivers side mirror, and I remember an attention getting honker horn used by Rodney Dangerfield in Caddy Shack. You'll have to trace it back as far as you can, find out where the last known good connection is, and if you can't find the broken wire, run another wire to the horn from the last good location where you can measure voltage. You may need a helper to push the horn down as you measure for 12V, or use an ohm gauge to ohm it out. Quote Link to comment Share on other sites More sharing options...
zero Posted July 29, 2014 Share Posted July 29, 2014 Last year I posted something about a broken horn and now, sadly my horn is broken again. I've tested steering column where the horn buttons are for power. It's showing 12v so I know power is going from there. Volt reading isn't going to tell you much unless you're testing for volts under load. As far as you finding 12 volts at the steering column??? Should not be any positive voltage there - ever. Not sure how or what you are testing. Horn goes "on" by being grounded by the horn-button. If a horn-button-switch goes bad - the horn gets no ground and will not work. Very easy to check. The horn itself has only two terminals. One is positive - hot all the time. The other gets grounded by the horn button when used. So if you suspect the horn button or steering column - all you need to do is ground he horn AT the horn. If it beeps - then you know there's a problem in the horn button circuit. Positive 12 power that goes to the horn ALL the time is in the stop-light circuit with a 20 amp fuse. If the brake-lights still work - then that circuit is powered. Somewhere between the fuse box and the horn - that power wires as green-red - bit then splits - and green-white goes to the horn and green-red goes to the brake lights. Quote Link to comment Share on other sites More sharing options...
5Toyota Posted July 29, 2014 Share Posted July 29, 2014 there is I think a horn relay sorry don't remember where it is located check wiring there Quote Link to comment Share on other sites More sharing options...
zero Posted July 29, 2014 Share Posted July 29, 2014 there is I think a horn relay sorry don't remember where it is located check wiring there No horn relay in a 1978 USA-version pickup. Quote Link to comment Share on other sites More sharing options...
mobilehippo Posted July 29, 2014 Author Share Posted July 29, 2014 Volt reading isn't going to tell you much unless you're testing for volts under load. As far as you finding 12 volts at the steering column??? Should not be any positive voltage there - ever. Not sure how or what you are testing. Horn goes "on" by being grounded by the horn-button. If a horn-button-switch goes bad - the horn gets no ground and will not work. Very easy to check. The horn itself has only two terminals. One is positive - hot all the time. The other gets grounded by the horn button when used. So if you suspect the horn button or steering column - all you need to do is ground he horn AT the horn. If it beeps - then you know there's a problem in the horn button circuit. Wouldn't there be power circulating so that when the horn gets ground then the horn will go off? When I mean steering column, there is a wire going to the buttons that when compressed will complete the circuit. The wire at this point on the steering wheel has power going to it. When I go over to the horn, and check the wires to see, if when the horn button is depressed, that the power goes through it, I am reading that there is no power. I guess I can check the brake light but I am pretty sure it's working. The fuses don't have any breaks it in when I pull them out. Maybe I'm missing something I don't know.... Quote Link to comment Share on other sites More sharing options...
Derek up North Posted July 29, 2014 Share Posted July 29, 2014 I refuse to comment unless someone can post a wiring diagram for your year Toyota. Quote Link to comment Share on other sites More sharing options...
linda s Posted July 30, 2014 Share Posted July 30, 2014 I refuse to comment unless someone can post a wiring diagram for your year Toyota. Like this? Nope link didn't go direct but the right diagram is down there somewhere 78 pickup and you can enlarge to see. Figure 42 Linda S http://www.autozone.com/autozone/repairinfo/repairguide/repairGuideContent.jsp?pageId=0900c1528004d7c3 Quote Link to comment Share on other sites More sharing options...
Maineah Posted July 30, 2014 Share Posted July 30, 2014 The older Toyota's used to wear out the contact button for the horn on the signal switch. Over the years I have put shims under the signal switch to move the contact close to the ring on the steering wheel the only other fix is to replace the switch. The steering wheel provides a ground for the horn through the contact. Quote Link to comment Share on other sites More sharing options...
zero Posted July 30, 2014 Share Posted July 30, 2014 I refuse to comment unless someone can post a wiring diagram for your year Toyota. I've posted the complete 1978 wiring diagram here for the 1978 truck several times. I assume it is still here somewhere. Quote Link to comment Share on other sites More sharing options...
zero Posted July 30, 2014 Share Posted July 30, 2014 I refuse to comment unless someone can post a wiring diagram for your year Toyota. Here is the relevant part again - from the Toyota 1978 factory wiring diagram book for USA and Canada trucks. The complete diagram is a fold-out and 5 pages wide. I've posted the complete thing twice here. Seems it ought to be archived somewhere. It's kind of a pain to stitch together 5 pages wide and I'm not doing it again - at least not right now. There is NO positive power in the steering column. The horn button grounds the horn to make it beep. Just like just about any other car or truck sold in the USA of that vintage. No horn relay in the 1978 Toyota. The images I posted previously were done on my scanner and better quality. I just did these with a hand-held camera. Quote Link to comment Share on other sites More sharing options...
Derek up North Posted July 30, 2014 Share Posted July 30, 2014 Like this? Yep, LIKE that one, but I don't see the horn shown. Maybe it's my eyes. Quote Link to comment Share on other sites More sharing options...
zero Posted July 30, 2014 Share Posted July 30, 2014 Yep, LIKE that one, but I don't see the horn shown. Maybe it's my eyes. Horn circuit is certainly in the images I just posted. Quote Link to comment Share on other sites More sharing options...
zero Posted July 30, 2014 Share Posted July 30, 2014 No glasses need here. Pretty simple circuit too. Quote Link to comment Share on other sites More sharing options...
Alvin Posted July 30, 2014 Share Posted July 30, 2014 As an electrical engineer, I draw circuits all day long. Just wanted to comment on the sad state of schematics drawn by mechanical engineers who feel the need to put everything in the vehicle on one page: We have this thing now called "Hierarchy" which allows us to place the entire circuit in a box at the top level. In this box, you would find a very rough block diagram, connected with live representations of harnesses. This really has only been the last 10 years when the software is advanced enough to do this, but you can keep dropping down through the hierarchy as deep as needed. For complicated systems (i.e. vehicle) we bust the schematic up into a working list of systems connected by name, or connected by harnesses. Sure cleans things up. It almost hurts to go back and look at the mess of unneeded lines used by ancestors in the days when schematics like this were needed. Okay... my comment didn't contribute squat... I'm glad we don't do it like this anymore. Quote Link to comment Share on other sites More sharing options...
zero Posted July 30, 2014 Share Posted July 30, 2014 As an electrical engineer, I draw circuits all day long. Just wanted to comment on the sad state of schematics drawn by mechanical engineers who feel the need to put everything in the vehicle on one page: We have this thing now called "Hierarchy" which allows us to place the entire circuit in a box at the top level. In this box, you would find a very rough block diagram, connected with live representations of harnesses. This really has only been the last 10 years when the software is advanced enough to do this, but you can keep dropping down through the hierarchy as deep as needed. For complicated systems (i.e. vehicle) we bust the schematic up into a working list of systems connected by name, or connected by harnesses. Sure cleans things up. It almost hurts to go back and look at the mess of unneeded lines used by ancestors in the days when schematics like this were needed. Okay... my comment didn't contribute squat... I'm glad we don't do it like this anymore. I understand what you are saying but can't say I've seen many examples in factory tech manuals. Condensed aftermarket manuals, yes. The 1978 Toyota factory manual I have is just a book of wiring diagrams and nothing else. The 1978 truck is 5 full pages of diagrams - not "all on one page." That is just the schematics. Also many pages of block diagrams for the same truck. Even more pages on types of connectors used and where they are located. More pages yet on sub-systems. My 1980s-1990s GM factory wiring books often have 20 pages of wiring diagrams for just one vehicle. I find the way Toyota did it with 5 full pages stitched together very easy to read and intuitive. Quote Link to comment Share on other sites More sharing options...
Derek up North Posted July 30, 2014 Share Posted July 30, 2014 Out of curiousity, why do you think Mechanical Engineers used to draw the electrical schematics? Quote Link to comment Share on other sites More sharing options...
zero Posted July 30, 2014 Share Posted July 30, 2014 Because the electrical engineers were too busy designing manual transmissions? Quote Link to comment Share on other sites More sharing options...
Alvin Posted July 30, 2014 Share Posted July 30, 2014 I've been in the business of designing ruggedized equipment for military and industry for almost 30 years. Over the years I've worked with dozens of EE's and dozens of ME's. There is a "style" employed by the ME's that is very recognizable which doesn't include the "tricks" of the trade that the EE's know to use... ME's are great and they're very talented, but when it comes to schematics, they do tend to spagetti wire everything all over the drawing (see schematics here as a good sample) while the EE drawings tend to be compartmentalized into multi-page hierarchical "snippet" drawings with a much heavier reliance on notes to indicate attributes and parameters such as wire type, colors, harness definitions, etc. Many of the ME's are car guys naturally and know tons and tons, but their schematics reflect more of a mechanical reliance on visually seeing the wire. Fewer port connectors, fewer off-page connectors, no "multi-channel design" (one page repeated over and over again for similar sub-circuits), and NEVER using a harness definition (this takes a bit of knowledge about the schematic tools, which can cost over $100,000.00 per license (Mentor Graphics with full blown extras) but not always... $6K will get you a good license of my favorite tool "Altium." I didn't mean it as any slight against ME's. Just that the style is so much harder to read. Would love to be able to include a recent sample but contracts prohibit that. I've included a link that illustrates some of the concepts. http://www.altium.com/files/altiumdesigner/s08/learningguides/tu0112%20creating%20a%20multi-channel%20design.pdf An optimal schematic might include 6 to 20 parts, all related to a given function, on a single page... with those pages connected at a higher level. Anyway, that's the flavor. How do you think that EE's are able to design chips with literally millions and billions of parts? They certainly don't create a schematic. Not anymore. Instead, they rely on the methods I've outlined above. Again, just wanted to say "yuck" lol Quote Link to comment Share on other sites More sharing options...
mobilehippo Posted July 30, 2014 Author Share Posted July 30, 2014 I will post some pictures tomorrow... I think I'm probably not explaining myself well here.... Quote Link to comment Share on other sites More sharing options...
Derek up North Posted July 30, 2014 Share Posted July 30, 2014 I love it when the wiring diagram fits on one page! Quote Link to comment Share on other sites More sharing options...
Maineah Posted July 30, 2014 Share Posted July 30, 2014 Last year I posted something about a broken horn and now, sadly my horn is broken again. I've tested steering column where the horn buttons are for power. It's showing 12v so I know power is going from there. However, the wires that connect the horn in the front of the car, is not showing power. So I know something is faulty with the power going from steering column to horn with the wires. I checked the fuses and they all seem to be fine. What do you guys suggest I do? I'm looking at the wiring and its quite complicated. Looks like spaghetti. Please help! Thanks! I understand what you are saying when the horn button is not grounded it will show 12 volt power in the steering column because it is just coming through the windings of the horn if you know where that wire is grounding it will make it beep. However it does not make sense that you have no power at the horn so either it's not the right wire or your connection to the horn with the meter is not a good one. There is a brass stud with a spring under it on the signal switch if you ground that it will complete the circuit to the horn. If it beeps the contact is worn enough that it is no longer touching the brass ring on the steering wheel. Quote Link to comment Share on other sites More sharing options...
zero Posted July 30, 2014 Share Posted July 30, 2014 In short - if the horn button circuit is the problem - all that needs to done for a test is this. Short to ground the pole on the horn that goes to the horn button. If it then "beeps" you know rest of the horn system is fine. A volt reading when not done under load is pretty useless on any circuit that is in question. Quote Link to comment Share on other sites More sharing options...
zero Posted July 30, 2014 Share Posted July 30, 2014 Some close photos of the 1978 steering wheel, rotating contact, ground buttons, etc. Quote Link to comment Share on other sites More sharing options...
zero Posted July 30, 2014 Share Posted July 30, 2014 I love it when the wiring diagram fits on one page! Here's the full "one page" for a 1978 Toyota truck. Schematic and harness diagram. Very well done by Toyota. Unlike the MGA though the "one page" is a five-page fold-out section. From "'Toyota Electrical Wiring Diagrams for USA and Canada 1978 Model", printed by Toyota Motor Sales Co. LTD. Copyright 1977 for Celica, Corona, Cressida, Pickup, and Land Cruiser destined for the U.S.A. and Canada. Printed December, 1977, Haruhi-mura, Nishikasugai-gun Aichi-Pref., Japan No. 98891 Quote Link to comment Share on other sites More sharing options...
Alvin Posted July 30, 2014 Share Posted July 30, 2014 Here's the full "one page" for a 1978 Toyota truck. Schematic and harness diagram. Very well done by Toyota. Unlike the MGA though the "one page" is a five-page fold-out section. From "'Toyota Electrical Wiring Diagrams for USA and Canada 1978 Model", printed by Toyota Motor Sales Co. LTD. Copyright 1977 for Celica, Corona, Cressida, Pickup, and Land Cruiser destined for the U.S.A. and Canada. Printed December, 1977, Haruhi-mura, Nishikasugai-gun Aichi-Pref., Japan No. 98891 As Buzz Lightyear said to Woody, "You're mocking me, aren't you." lol. Kidding. I knew I should have kept quiet. My Odyssey is a 1989 and it would be interesting to compare the differences to the 1978 truck. Have been tempted to put in an SR-5 dashboard. Quote Link to comment Share on other sites More sharing options...
zero Posted July 30, 2014 Share Posted July 30, 2014 As Buzz Lightyear said to Woody, "You're mocking me, aren't you." lol. Kidding. I knew I should have kept quiet. My Odyssey is a 1989 and it would be interesting to compare the differences to the 1978 truck. Have been tempted to put in an SR-5 dashboard. 1989 uses twin horns and a horn relay. 1978 has one horn and no relay - just wired direct. Quote Link to comment Share on other sites More sharing options...
mobilehippo Posted July 30, 2014 Author Share Posted July 30, 2014 Some close photos of the 1978 steering wheel, rotating contact, ground buttons, etc. Yes this is how my horn buttons look like. Yes I have tried to ground the wires in the steering wheel manually, like putting the wire staight to the ground column and the horn does not blow. That is why I am saying there is no power going to the horn at the front of the vehicle because when I ground the horn wires, nothing happens... Also I checked to see if power is coming from the wires at the front of the car where the horns are and I don't get any readings. So I am assuming the problem is one to do with the wiring??? Quote Link to comment Share on other sites More sharing options...
WME Posted July 30, 2014 Share Posted July 30, 2014 Use a jumper and apply 12v to the horn where the GW wire goes. Remove the wire first then jumper. Then honk the horn and see if it works. Quote Link to comment Share on other sites More sharing options...
Alvin Posted July 30, 2014 Share Posted July 30, 2014 Wonder if blowing into the horn would cause 12V to appear at the terminals? Sorry couldn't resist. Quote Link to comment Share on other sites More sharing options...
mobilehippo Posted July 30, 2014 Author Share Posted July 30, 2014 Yeah I hard wired the horn to my car battery and yes it does blow... Use a jumper and apply 12v to the horn where the GW wire goes. Remove the wire first then jumper. Then honk the horn and see if it works. Quote Link to comment Share on other sites More sharing options...
zero Posted July 30, 2014 Share Posted July 30, 2014 Yes this is how my horn buttons look like. Yes I have tried to ground the wires in the steering wheel manually, like putting the wire staight to the ground column and the horn does not blow. That is why I am saying there is no power going to the horn at the front of the vehicle because when I ground the horn wires, nothing happens... Also I checked to see if power is coming from the wires at the front of the car where the horns are and I don't get any readings. So I am assuming the problem is one to do with the wiring??? Horn just has two terminals. Put 12 volts positive to one and 12 volts negative to the other - and it will beep IF it works. Horns have metal moving parts and don't last forever. Don't last long at all where I live. You might just have a bad horn. Quote Link to comment Share on other sites More sharing options...
zero Posted July 30, 2014 Share Posted July 30, 2014 Sorry. Didn't read your last post about how you hooked the battery to the horn and tested it. Quote Link to comment Share on other sites More sharing options...
WME Posted July 30, 2014 Share Posted July 30, 2014 OK so that side of your horn is OK. Now start back tracing the GW wire to see where it looses power. It may have been pinched by a bolt at some time.. If all else fails run new wire from the fuse box. Quote Link to comment Share on other sites More sharing options...
Maineah Posted July 30, 2014 Share Posted July 30, 2014 Hazard flasher work? Quote Link to comment Share on other sites More sharing options...
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