cleaning 96 and 97 LX450 and land cruiser steering wheel for intermittent horn

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i'm tracking down a non working and now intermittent horn.
it looks like there are two electrically isolated spring mounted "bars" on the left and the right and four square bronze contacts (and a facing rivet) at the four "corners" here. i am going to go in on my spare wheel and Deoxit all of those to make sure they are clean.
also there is a black wire that runs into the connector that is mounted in the RIGHT bar only that goes to the connector to the clock spring (for the cruise control and the telephone on the LX450).
anyone know how test that wire for continuity? i use Ohm setting i think?
also anyone have any other specifics on testing this wire? the airbag will be off and the battery will not be working. can i reconnect the battery and test the horn with the airbag off while jiggling the wire?
anything else?
ALSO, anyone know how the LEFT bar triggers the horn? i can't see how pushing that left bar down would send an electrical impulse through the wiring to the clock spring and into the horn?
THANKS

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First things first: you want to prevent the airbag from deploying while you're working on it. The FSM says to place it face up (the way you see it in the driver's seat) inside a stack of tires. I'm not saying you have to do this, but this is how important Toyota thinks it is to protect the techs while they are working on the truck. Be careful, don't work on the electrical system while the airbag is connected to it and don't drop the thing.

Second, realize that if you remove the airbag from the electrical circuit, and then reconnect the battery (which should, in all cases, be disconnected while you're working on the steering column), the system will generate an SRS fault which you have to clear, after you complete whatever work you're doing. You can disconnect the airbag, do work, and reconnect it, before reconnecting that battery, and, in a perfect world, not get a fault. But you will definitely get a fault if the battery is connected without the airbag in the circuit. This is by design; it's the same condition as the airbag not functioning electrically, which is what you want, so you know you have a good airbag.

Third, yes you use the OHM setting to test continuity.

I've attached the diagrams for your use.
 

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Reading the EWD, you check the Green/Orange (green with orange stripe, main color is always first, stripe is always second) wire and the Green/White wire for continuity when the horn switch is closed. If there is continuity, the relay is good. This is the long way of saying what the SERVICE HINTS box tells you.

FWIW, what you're doing when you "sound" the horn is grounding the circuit. This is the way all Toyota circuits work on the LandCruiser. If there's one that doesn't work this way, I've haven't seen it yet. You can test the circuit which you feel should work, but doesn't by finding another ground. If that works, the internal (circuit) ground path is open. Any screw/bolt near you that has a wire terminal visibly on it is a ground.
 
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First things first: you want to prevent the airbag from deploying while you're working on it. The FSM says to place it face up (the way you see it in the driver's seat) inside a stack of tires. I'm not saying you have to do this, but this is how important Toyota thinks it is to protect the techs while they are working on the truck. Be careful, don't work on the electrical system while the airbag is connected to it and don't drop the thing.

Second, realize that if you remove the airbag from the electrical circuit, and then reconnect the battery (which should, in all cases, be disconnected while you're working on the steering column), the system will generate an SRS fault which you have to clear, after you complete whatever work you're doing. You can disconnect the airbag, do work, and reconnect it, before reconnecting that battery, and, in a perfect world, not get a fault. But you will definitely get a fault if the battery is connected without the airbag in the circuit. This is by design; it's the same condition as the airbag not functioning electrically, which is what you want, so you know you have a good airbag.

Third, yes you use the OHM setting to test continuity.

I've attached the diagrams for your use.
hey man. thanks for a great answer. i started thinking i won't reconnect the battery while the airbag is out out of an abundance of caution. one video said you should ground yourself before touching the airbag and it just doesn't seem with it.
i can test continuity on the black wire (and wiggle it around) with just the horn and my multimeter on a bench i think.
do i clean those bronze or brass contexts with deoxit i guess?
also do you happen to know how the left "bar" on the wheel triggers the horn? it seems like it is electrically isolated from the rest of the system and i am not quite sure i see how it sends electrics power to the horn even when the brass/bronze contacts are touching?
or i guess it goes through the metal casting to the right side and into the metals support
bracket and then on through the black wire to the harness? it's kind of confusing actually.
green crosses are where the contacts are. yellow is the black wire that is soldered to the support bracket.

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^this (it's why I gave you the relay circuit).

AFAIK, the horn grounds are connected to each other through the steering wheel, but I could be wrong, I've never traced it.

I use emery, or crocus cloth, or an emery board (whichever is closer to hand) to clean contacts (you need to remove ALL the residue when you do this, or it'll just rebind itself to the terminal substrate). I only spray things I can't reach, and only as a last resort. It never works as well for me as abrasion. Back in the dark ages, we used to clean light corrosion on radio contacts with an artgum eraser on a number 2 pencil; it never failed. And never lasted more than one field problem.
 
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Did you check the simple things first like the horn relay??
yeah. it was awhile ago but i would have cleaned the ground at the firm and whatever i could get my hands on. listened for a click at the relay. and pulled the relay. i probably would have tried to lightly sand the spades etc.
it works when and if it feels like it now. it's almost like it is streaky in that it will work perfectly for a lengthy period of time. then not work at all. then kind of work if you keep mashing on it with no apparent rhyme or reason.
one day it worked fine when i tried it.
i've got a loaner steering wheel so i am going to put mine back in and see what i find.
 
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Reading the EWD, you check the Green/Orange (green with orange stripe, main color is always first, stripe is always second) wire and the Green/White wire for continuity when the horn switch is closed. If there is continuity, the relay is good. This is the long way of saying what the SERVICE HINTS box tells you.

FWIW, what you're doing when you "sound" the horn is grounding the circuit. This is the way all Toyota circuits work on the LandCruiser. If there's one that doesn't work this way, I've haven't seen it yet. You can test the circuit which you feel should work, but doesn't by finding another ground. If that works, the internal (circuit) ground path is open. Any screw/bolt near you that has a wire terminal visibly on it is a ground.
hey malleus.

thanks a lot for this. i am going to print out your PDF's and i do have the electrical manual i can pull out and study tomorrow.

just while i get started i pulled off the plastic cover in the back with the four screws. i sanded down the four square bronze contacts and the little rivet type contacts.

now i am in the harness with the black probe and i was able to grab the little solder that is onto what i am calling the "right BAR". there are two "bars" but only ones has the wire from the harness soldered to it.

anyway from the soldered wire in the back of this bar - with COM, V/Ohm, and on the Ohm setting and i get 0.2 Ohms.

can you help me with what that means?

i did test the other five terminals in the harness and i get OL on all of these.

all the images below show the black prob in the terminal at the black wire. then i tested the termination point of the wire in the solder (0.2 Ohm), then on the metal bar (14 Ohm), closer to the solder on the metal bar (24 Ohm or something), ams then on the casting that holds everything together but is isolated from the left and right bars is OL which i guess is to be expected.

just trying to bootstrap myself here a little.

THANKS

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Reading the EWD, you check the Green/Orange (green with orange stripe, main color is always first, stripe is always second) wire and the Green/White wire for continuity when the horn switch is closed. If there is continuity, the relay is good. This is the long way of saying what the SERVICE HINTS box tells you.

FWIW, what you're doing when you "sound" the horn is grounding the circuit. This is the way all Toyota circuits work on the LandCruiser. If there's one that doesn't work this way, I've haven't seen it yet. You can test the circuit which you feel should work, but doesn't by finding another ground. If that works, the internal (circuit) ground path is open. Any screw/bolt near you that has a wire terminal visibly on it is a ground.
so here i am just trying to test a couple things (and learn).
the bar on the right will sound with continuity on the top context and the bottom contact when i push the bar in and make contact. the one on the left does not "make continuity" at all which i guess is sort of to be expected since there is nothing making contact with the bar on the left.
basically the metal casting - i think - closes the circuit with the black wire on the bar on the right. but since there is not wire to the bar on the left pushing it in and closing the contexts does nothing?
anyway i did a video and include screenshots from it.
the green plus symbols show wheee i get continuity on the right and the red negative symbols show where i don't get continuity even though there are the same contexts on the left bar.
 
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so here i am just trying to test a couple things (and learn).
the bar on the right will sound with continuity on the top context and the bottom contact when i push the bar in and make contact. the one on the left does not "make continuity" at all which i guess is sort of to be expected since there is nothing making contact with the bar on the left.
basically the metal casting - i think - closes the circuit with the black wire on the bar on the right. but since there is not wire to the bar on the left pushing it in and closing the contexts does nothing?
anyway i did a video and include screenshots from it.
the green plus symbols show wheee i get continuity on the right and the red negative symbols show where i don't get continuity even though there are the same contexts on the left bar.
pics

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hey malleus.

thanks a lot for this. i am going to print out your PDF's and i do have the electrical manual i can pull out and study tomorrow.

just while i get started i pulled off the plastic cover in the back with the four screws. i sanded down the four square bronze contacts and the little rivet type contacts.

now i am in the harness with the black probe and i was able to grab the little solder that is onto what i am calling the "right BAR". there are two "bars" but only ones has the wire from the harness soldered to it.

anyway from the soldered wire in the back of this bar - with COM, V/Ohm, and on the Ohm setting and i get 0.2 Ohms.

can you help me with what that means?

i did test the other five terminals in the harness and i get OL on all of these.

all the images below show the black prob in the terminal at the black wire. then i tested the termination point of the wire in the solder (0.2 Ohm), then on the metal bar (14 Ohm), closer to the solder on the metal bar (24 Ohm or something), ams then on the casting that holds everything together but is isolated from the left and right bars is OL which i guess is to be expected.

just trying to bootstrap myself here a little.

THANKS

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OL means an open circuit. Any value means there is conductivity. If it's important, the EWD will tell you what it should be.
 
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so here i am just trying to test a couple things (and learn).
the bar on the right will sound with continuity on the top context and the bottom contact when i push the bar in and make contact. the one on the left does not "make continuity" at all which i guess is sort of to be expected since there is nothing making contact with the bar on the left.
basically the metal casting - i think - closes the circuit with the black wire on the bar on the right. but since there is not wire to the bar on the left pushing it in and closing the contexts does nothing?
anyway i did a video and include screenshots from it.
the green plus symbols show wheee i get continuity on the right and the red negative symbols show where i don't get continuity even though there are the same contexts on the left bar.
sounds right
 
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OL means an open circuit. Any value means there is conductivity. If it's important, the EWD will tell you what it should be.
the black wire from the harness is soldered to the underside of the bar on the right. there is no wire making contact with the bar on the left.
this means that even though there are two contact points at the end of each metal bar - only the bar in the right creates continuity. if you depress the bar on the left and make contact with the contacts there is no continuity created.
i have a video i can try to upload somewhere to make this more understandable.
but it's curious that the bar on the left will not make the horn sound.

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OL means an open circuit. Any value means there is conductivity. If it's important, the EWD will tell you what it should be.
hi malleus,
here is a video where i am trying to explain the issue with the right versus left contact points. the two right contact points will sound the horn it appears but the two left contact points won't sound the horn? this seems very weird to me since the bar on the left has two contact points then that don't work.
 
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malleus, all.
another question please. the horn is intermittent. now it is not working most of the time though.
i have checked and then just replaced the bladed fuse. it is a fuse for the horn and the hazards and since the hazards work i also have to assume it works.
also i can confirm that the relay is clicking. it seems to click any time you push the airbag.
so now it seems i am moving on to the wiring between the relay and the horn?
if so what is the proper way to test at the horn please to check voltage? i guess i will check that toyota document posted. i have removed the horn and cleaned contacts and cleaned ehe ground but i mean maybe the actual horns are bad.

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So you have a couple of items to check here. You've gone through most of this, but bear with me.

My approach, unless I know a likely problem exists, is to check all the easy/accessible components first. Even if they aren't likely, you can eliminate a lot of intermittent problems this way. Professional technicians don't work this way, because it is the most time consuming method of problem solving and they are paid by the hour. You aren't. This is, though, the best way to familiarize yourself with the system as a whole and more understanding is always better.

So, in this case, check the horns and relay. Since they're both 12VDC, you can use a jumper wire from the battery to activate them. However, this should be done after disconnecting the battery from the vehicle wiring harness, to ensure you don't inadvertently short a circuit and kill something not already dead. Pros bench test with a separate battery, or power source, but I don't have one, and I'd bet most people don't either.

If you're serious about troubleshooting the electrical system, you need a dedicated toolkit. It isn't much, but it is more than handy. One of the first tools you need are jumpers. You should use wire at least 12 gauge. I have used 14ga wire, but I don't like it. Electrically, for a low amperage system like the truck, it'll work, but 14ga is mostly multistrand and it breaks really easy. If you have to use it, use at least solid conductor wire. Same goes for the 12ga stuff. Theses jumpers should be about 12-15in long and have alligator clips on each end. If you get really froggy and start chasing open circuits in connectors, you'll need jumpers with the proper terminal ends, but that's for later.

So now you have jumpers, a disconnected battery and two electrical devices to check: horns and relay. The horn is easy; power to one terminal, ground the other and if it makes noise, it's good. The relay needs a little more care. You need to check the terminal positions against the EWD to locate which terminals you want power to and which to ground. The relay is a switch, so you'll hear it click when it has a complete circuit and it works. No click = bad relay; just make sure you connect the correct terminals to power and ground or it won't work.
 
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The big picture here is to make a plan and work methodically through it. Don't jump around and throw parts at a problem; while that is a plan, it's probably not the most effective or efficient.

I assume you:
have a good battery connection, and clean terminals (that's always the first step in solving an electrical problem for me);
checked your fuse, and it's good (you said you did, and it is).

So you have power, good horns and a good relay.

Now the problem is limited to the steering wheel contacts and the harness. This is where the EWD is helpful. There is also a chart with the conectors for each circuit in the EWD, at the end of each section. Don't blow that off, sometimes it's the key to solving a problem.

The steering wheel is obviously easier to check so that's next on the list. I'm doing this from memory, but I think the switch contacts are only on one side, so the contact surfaces should be clean and shiny and there should be the following circuit:
(a) No continuity between the switch contacts when they are open (obvious, I know, but that's how flowcharts work)
(b) Continuity between the switch contacts when they are closed

If both those conditions are met, the steering wheel switch is good, and you are left with the bane of every electrical problem: a loose connection somewhere. The only was to find it/them (remember it could be more than one) is to start at one end and work your way to the other - steering wheel to battery, or vice versa. Inspect all wires (that you can see) and make sure the insulation is intact. Check for continuity between both ends of each wire and connector. If there is a fault, you'll find it. It's much easier to say than do, sometimes.

HTH
 
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So I wrote all that without looking at the circuit diagram, so here a few nuggets:

The connector (C14 on the EWD) terminals 9, 10 are for the horn circuit. This connector is tucked under the column. Terminals 9,10 in the connector are the connection to ground. FWIW, the terminals in the connector are numbered to to bottom, left to right in the female half (the male is opposite). If the connector diagram has a X in a terminal spot, there's no conductor/terminal there. A dot means there is. The convention Toyota uses in these EWDs is the terminals in the connectors pertinent to the circuit you are looking at are numbered. These numbers correspond to the circuit diagram.

The ground, for this circuit, is behind the plastic kick panel cover, next to your left foot position when driving. It woudn't hurt to remove the scre, clean both the sheetmetal panel and ring terminal and reassemble. You can check the ground by connecting the other end of that wire to your DMM and the ground lead (of the DMM) to another screw in the panel somewhere. If you have a good ground you'll see it (or hear it, depending on your DMM).

The other information on the bottom of the page refer to the groundpoints, connector joining and relay diagrams, which are also handy to have. They are in the EWD; look for it in the Resources section.

Since you have observed the horn/warning flasher is on the same circuit, and the flashers, relay and horns work, the problem is probably limited to the horn circuit between the steering wheel and the ground at the kickpanel.
 

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