Steering Column Ground

[ScubaSteve]

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?

[Gary Lewis]

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.

[ScubaSteve]

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?

[Gary Lewis]

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.

[85lebaront2]

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.

[Gary Lewis]

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.

[ScubaSteve]

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.

[Gary Lewis]

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.

[ScubaSteve]

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.

[Gary Lewis]

Ok.  And you are sticking the clip on the black wire into one of the bolt holes?

[ScubaSteve]

Yep the ground is plugged into the bolt hole. I just installed a new switch assembly and still no luck. The steering shaft has no connection to ground. The outside of the steering column has a good ground it just never get to the shaft. I needed the switch replaced anyway so nothing lost on that but I don’t know where to go next. I see some info on the older trucks having a jumper wire around the rag joint to make connections did the 86 models have anything like this?

[Gary Lewis]

No, they didn't have anything on the rag joint.

If it was me, I'd test by pulling the two Phillips screws to take the horn pad off.  Then I'd use a jumper from the black wire, after pulling it out of the threaded hole, to a known ground.  And leave the other two wires connected.  See if the horn works then with the key off and with it on.

That basically bypasses the ground wire to the brush, the brush itself, and the slip ring in the wheel.  If it works then you know the problem is in that ground circuit.  If not, it is elsewhere.

Meanwhile I'll see if I can figure out how/where the ground wire is.  But I already know that the true wiring diagrams don't help - they don't even show the slip rings and brushes.  

[ScubaSteve]

Jumping the black wire to a good ground the horn works key on or off. I am trying my best to keep from mounting a horn button on the dash or steering column but I'm getting to that point. Thanks again for all your time.

[Gary Lewis]

Ok, we are making progress.  Now to find out why that brush isn't grounded......


Welcome.

[85lebaront2]

The one nearest the shaft is not a brush, it is the pin for the turn signal cancel cam, it goes into a slot on the bottom side of the wheel hub, the only brushes I have ever seen are the pair you have one with yellow/blue, the other with blue. Even the 1996 F350 column only uses two brushes, ground is the hub of the steering wheel.

I don't remember on the old column, but the newer columns and my Chrysler have a ground tab at one of the mounting bolts (the Chrysler also has a horn ground wire).

[Steve83]

85lebaront2 wrote

The one nearest the shaft is not a brush, it is the pin for the turn signal cancel cam...

I agree.

I don't remember specifically because it's been so long since I used that column & cruise system, but I think the steering shaft grounded either through the column's top bearing (near the wheel) or the rag joint (which should have steel mesh embedded in the rag).  I might still have one of those old columns here to check, but I doubt I have that kind of rag joint.

In the meantime, read this caption & follow the links:

[Gary Lewis]

Ok, I WAS WRONG!  What I thought was the ground brush is, indeed, the pin for the turn signal cancel cam.  And ground goes through the hub of the steering wheel.  

Now, for my findings with chasing the ground on my two spare columns.  One of them does not have connectivity from the shaft to anything.  But, I do get a capacitor effect when I try to check for connectivity from it to the mounting bracket, which tells me that there are surfaces that are probably quite close but not touching or have a very high impedance between them, like grease.  However, I don't get the capacitor effect on any other surface, nor on any of the wires coming from the column.

On the other column, the one from Dad's truck, there is connectivity from the hub of the steering wheel to the aluminum mounting bracket - most of the time.  But if I move the wheel just right I lose the connectivity and get the capacitor effect.  And, when I have connectivity to the mounting bracket there's no connectivity to anything else, like the ignition switch, its mounts, or any of its terminals.  Nor the wires coming out of the column, nor to the mount that goes to the firewall or the rag joint or lower shaft.

So, I surmise that the ground goes through the aluminum mounting bracket.  And it must go through the upper bearing, like Steve suggested.  

ScubaSteve - Do you use the speed control?  If not, you could make a slight wiring change and the horn should work properly.

[ScubaSteve]

I never used the speed control on this truck but only because it never worked. I think I will add a ground wire to the rag joint and see how that works out.

Thanks a bunch for all the help. I’ll keep you posted on the progress.

[Gary Lewis]

You'll have to have a wire that will wrap around the rag joint.  But it might work.

And my other idea will work if you want to explore it.  Just requires you to pull the light blue/black wire out of the connector on the pigtail coming out of the steering column and placing a light bulb on it to ground.  (Don't take it directly to ground.)  The current going through it will be enough to pull the horn relay in.

And, if you decide to fix the speed control you can put the wire back in the connector.

[85lebaront2]

I actually have a tester for the vacuum speed control, my son used it to test the one on his 86 and I used it to test the one on my 1994 Taurus.