ScubaSteve Posted September 16, 2018 Share Posted September 16, 2018 I am trying to chase down a problem with my horn. It will only work with the key off and I find when the key is off it grounds through the steering wheel lock. How does the steering shaft ground? Link to comment Share on other sites More sharing options...
Gary Lewis Posted September 17, 2018 Share Posted September 17, 2018 I have a page on ground wires: http://www.garysgaragemahal.com/ground-wires.html. And the 1986 EVTM has this page on grounds: http://www.garysgaragemahal.com/grounds.html But I do not think there is a ground for the steering column itself. The horn grounds through the ground brush in the steering wheel, as you can see here: http://www.garysgaragemahal.com/horn--cigar-lighter.html. I once had a problem just like yours where the horn would honk when the key was off, but not when it was on. Turned out that the ground brush was bad and the horn relay was grounding through the speed control. But, when the key was on the speed control was powered and did not provide a ground. Link to comment Share on other sites More sharing options...
ScubaSteve Posted September 17, 2018 Author Share Posted September 17, 2018 I have a page on ground wires: http://www.garysgaragemahal.com/ground-wires.html. And the 1986 EVTM has this page on grounds: http://www.garysgaragemahal.com/grounds.html But I do not think there is a ground for the steering column itself. The horn grounds through the ground brush in the steering wheel, as you can see here: http://www.garysgaragemahal.com/horn--cigar-lighter.html. I once had a problem just like yours where the horn would honk when the key was off, but not when it was on. Turned out that the ground brush was bad and the horn relay was grounding through the speed control. But, when the key was on the speed control was powered and did not provide a ground. The schematics I have found including yours do not have the same colors for the wires. I wonder if someone has switched columns as the truck is an XLT Lariat but does not have a tilt wheel. When it shows the ground brushes I assume that's the two brushes right behind the steering wheel switch. On my truck I have the yellow wire that is hot all the time and a blue wire that I think goes to the cruse control. The yellow wire connects to the horn button and then I have a black wire that connects the horn button to the steering shaft for a ground. The steering shaft and steering wheel have no ground and I cant figure out how it should be grounded. Is there another ground on the column? I see in the schematic it says ground brush "On Steering Column" is this one of the two brushes behind the wheel? Link to comment Share on other sites More sharing options...
Gary Lewis Posted September 17, 2018 Share Posted September 17, 2018 The schematics I have found including yours do not have the same colors for the wires. I wonder if someone has switched columns as the truck is an XLT Lariat but does not have a tilt wheel. When it shows the ground brushes I assume that's the two brushes right behind the steering wheel switch. On my truck I have the yellow wire that is hot all the time and a blue wire that I think goes to the cruse control. The yellow wire connects to the horn button and then I have a black wire that connects the horn button to the steering shaft for a ground. The steering shaft and steering wheel have no ground and I cant figure out how it should be grounded. Is there another ground on the column? I see in the schematic it says ground brush "On Steering Column" is this one of the two brushes behind the wheel? If your truck has speed control it should have 3 brushes in the steering column. Look at Page 135 here in the '86 EVTM: http://www.garysgaragemahal.com/speed-control1.html. So it seems like someone swapped the column, and that one doesn't have the 3-brush setup for cruise. Link to comment Share on other sites More sharing options...
85lebaront2 Posted September 17, 2018 Share Posted September 17, 2018 If your truck has speed control it should have 3 brushes in the steering column. Look at Page 135 here in the '86 EVTM: http://www.garysgaragemahal.com/speed-control1.html. So it seems like someone swapped the column, and that one doesn't have the 3-brush setup for cruise. I know the diagrams show 3 brushes, but I only remember 2, the ground being the steering shaft I believe, in fact I think even the later trucks were similar except the air bag models used the clockspring to carry the signal. I will look at my spare column later, but one thing I do not see on those diagrams is the horn relay. I am pretty sure that the horn relay was only used with a speed control. Without speed control you had a yellow wire and a blue wire to the brushes and the horn was operated by connecting them together. With speed control the the yellow wire was from the relay coil and grounding it activated the horn. Speed control is operated by a series of resistors that connected to either ground or 12V through the horn relay coil provide signal to the speed control amplifier on trucks through 1992, and the speed control unit (electronics and servo motor) 1993 on until the drive by wire models. 1992 and on, all had a horn relay in the PDC. The horn/lighter link shows the horn relay for speed control models as I remembered. Link to comment Share on other sites More sharing options...
Gary Lewis Posted September 17, 2018 Share Posted September 17, 2018 I know the diagrams show 3 brushes, but I only remember 2, the ground being the steering shaft I believe, in fact I think even the later trucks were similar except the air bag models used the clockspring to carry the signal. I will look at my spare column later, but one thing I do not see on those diagrams is the horn relay. I am pretty sure that the horn relay was only used with a speed control. Without speed control you had a yellow wire and a blue wire to the brushes and the horn was operated by connecting them together. With speed control the the yellow wire was from the relay coil and grounding it activated the horn. Speed control is operated by a series of resistors that connected to either ground or 12V through the horn relay coil provide signal to the speed control amplifier on trucks through 1992, and the speed control unit (electronics and servo motor) 1993 on until the drive by wire models. 1992 and on, all had a horn relay in the PDC. The horn/lighter link shows the horn relay for speed control models as I remembered. Bill - Yes, the horn relay was only used with a speed control, and actually mounted on the speed control's electronics. And, check pages 108 & 135 of your '86 EVTM for the horn with and without a relay. (At least unless when I scanned your EVTM I somehow added that info. ) As for three brushes, here's my spare column, with the one circled in red being the ground, the one in yellow being power, and the one in blue going to the speed control. Link to comment Share on other sites More sharing options...
ScubaSteve Posted September 17, 2018 Author Share Posted September 17, 2018 Bill - Yes, the horn relay was only used with a speed control, and actually mounted on the speed control's electronics. And, check pages 108 & 135 of your '86 EVTM for the horn with and without a relay. (At least unless when I scanned your EVTM I somehow added that info. ) As for three brushes, here's my spare column, with the one circled in red being the ground, the one in yellow being power, and the one in blue going to the speed control. So the little peg with the red circle is actually a brush? I thought that was just a peg for steering cancel to engage with the steering wheel, but if that's my ground brush that's my problem because I have zero continuity through it. I guess that will come with a new switch assembly? Thanks a bunch for the help. Link to comment Share on other sites More sharing options...
Gary Lewis Posted September 17, 2018 Share Posted September 17, 2018 Bill - Yes, the horn relay was only used with a speed control, and actually mounted on the speed control's electronics. And, check pages 108 & 135 of your '86 EVTM for the horn with and without a relay. (At least unless when I scanned your EVTM I somehow added that info. ) As for three brushes, here's my spare column, with the one circled in red being the ground, the one in yellow being power, and the one in blue going to the speed control. Steve - Do you have a standard, non-speed control horn pad on your truck? I ask, because I am certain that having one of those on a truck with speed control will cause the problem you have. Been there, done that. A standard horn pad just has a single switch in it and it connects the dark blue wire to the yellow/light blue wire, which puts battery voltage to the horn. There is no ground or black wire for that horn pad. So, if you put a standard pad on a truck with speed control all you are doing is connecting the DB wire to the light blue/black (LB/Bk) wire, as shown below. And with the key off there's no power to the speed control and it sinks enough power to pull the horn relay in and the horn honks. But with the key on there's power to the speed control and it no longer sinks enough power to pull the relay in. Link to comment Share on other sites More sharing options...
ScubaSteve Posted September 17, 2018 Author Share Posted September 17, 2018 Steve - Do you have a standard, non-speed control horn pad on your truck? I ask, because I am certain that having one of those on a truck with speed control will cause the problem you have. Been there, done that. A standard horn pad just has a single switch in it and it connects the dark blue wire to the yellow/light blue wire, which puts battery voltage to the horn. There is no ground or black wire for that horn pad. So, if you put a standard pad on a truck with speed control all you are doing is connecting the DB wire to the light blue/black (LB/Bk) wire, as shown below. And with the key off there's no power to the speed control and it sinks enough power to pull the horn relay in and the horn honks. But with the key on there's power to the speed control and it no longer sinks enough power to pull the relay in. Its has speed control and the original horn pad with speed control. I see how having the wrong horn pad could be a problem. I have to replace my turn signal switch because the cancel is broken so I hope that may also fix my grounding issue. Link to comment Share on other sites More sharing options...
Gary Lewis Posted September 17, 2018 Share Posted September 17, 2018 Its has speed control and the original horn pad with speed control. I see how having the wrong horn pad could be a problem. I have to replace my turn signal switch because the cancel is broken so I hope that may also fix my grounding issue. Ok. And you are sticking the clip on the black wire into one of the bolt holes? Link to comment Share on other sites More sharing options...
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