Horn intermittent

[on2wheels]

Hi,
I have an intermittent horn, don't laugh!
Sequence of events.........
Upper steering bushed replaced by local garage.
Super job, good steering feel.
Now horn works when cold but not after a 10 mile drive.
It is difficult to tie the above (replacement bushes with horn problem) when you only drive the car at maximum once a week.
Get back to my garage to fault find, car cools down, horn works. AGH**
I have removed horn push and show it below.
I know it is not as the manual states but it looks as though it should be ok.
Horn push sits ontop of spring.
Horn push shorts centre spindle to earth when depressed.
Possible causes please.
Loose wires?
Dodgy relay?
Fuse?
Bad earth on horn?
Something wrong in steering column? This is the bit I fear. Even if the centre spindle has earth put on it can it get lost further down the shaft?
Nick.

[christopher storey]

First suspect is relay since this will be in a position most likely to receive copious quantities of heat . You should be able to check this reasonably easily by getting the car good and warm and then getting someone else to press the button ( or use a wire to short the spindle to earth, which is a check which I suggest you perform anyway when hot) when you should hear/feel the relay click. If it clicks but there is no horn, then it is likely to be a relay which goes open circuit on the current delivery side when hot . If there is no click, then you have to look further back up the earthing circuit, and also check that when hot the insulated spindle is receiving 12v. If there is any problem with this, you need to check the voltage from its source which IIRC includes a series of rather fiddly copper contacts under the steering wheel , and possibly also a slotted circumferential one but I cannot be sure about this . Check for voltage on these contacts through from the wires which feed in through the indicator switch . You will see everything more clearly if you remove the switch which is held by two 180 degree clips which are screwed together top and bottom . Check also that the metal top hat in the button is seating correctly , as this is another common source of trouble . Also, just as a matter of interest , what are those three radial holes drilled in the wheel?

[on2wheels]

Thanks Chris,
Thank you for your comprehensive reply.
I too hope it is the relay. I will get onto it and let you know when I have an outcome.
As for the holes in the steering wheel, I am not responsible.
Could it be for another method of attaching the horn push?
Looks like a genuine steering wheel, but could it have come off something else?
It has the finger indentations on the under side.



Nick.

[Dave K]

I have had this problem on and off and last year found out the problem it was the small spring that sits inside the steering column.
It had somehow come out and wrapped itself around the plastic bush.
You can't buy replacement springs but I used the spring from a ball point pen and it now works perfectly.
It's not that hard to drop the whole assembly and check the internals.

You might also want to check the plug where it goes in the bonnet under pan.
Checking the relay is easy just switch on the ignition and push the horn, if it clicks its OK if not its not OK.

Dave

[on2wheels]

Hi,
Outcome as promised.

Not the relay.

Poor contact between slip ring and ...........?
Not sure how it works, or what the little spring is for.
Pressing the slip ring, to make better contact, helps restore the horn.
This was done without any dismantling. Poked screwdriver through gap in steering column, down by the knees!
Not sure if fix is permanent.

Nick.

[Larry Wade]

Hi Nick,

Is it fixed yet?

If not could you clarify what you mean by intermediate? Do you mean that the horn spontaneously goes off or do you mean that sometimes it doesn't work when pressed?

Best wishes,
Larry

[Larry Wade]

Oops. Sorry Nick,

I just read your first message closely and you had the information needed.

If it's not fixed and its the slip contact the problem may be with the parts. The original contacts were beryllium copper which is a great spring material. The new ones are regular copper, which is a lousy spring material. The BeCu will stay in contact. Regular copper will relax to wherever it's held and not spring back.

I don't know anybody who is selling new ones made from the right material. I purchased from SNG Barrett and couldn't use their part. I think I'd try hard to get one from a junk yard or get one made.

The reason the BeCu isn't widely available any more is that a small portion of the population can have a very severe (even terminal) allergic reaction to small bits of the metal that are inhaled. Keep that in mind should you decide to make your own contact.

Larry

[on2wheels]

Hi Larry,
Thanks for your interest.
It was the slip ring making poor contact that caused the horn to fail sometimes.
From your reply I guess it is made of copper as it is making poor contact.
The shaft it is riding round looks slightly corroded, so maybe that is part of the problem.
Anyway I can get it going when I want to!

Nick.

[on2wheels]

Hi,
Yes it appears to be the slip ring making poor contact with the shaft.
When I press slip ring, contact is re-made and horn sounds.



By the way, does anyone know why this aperture was created in the shaft?
I expect it is to be found on all examples of the same era?

[Heuer]

Sounds as though the small spring (4th from left, below) is weak or sticking. Suggest you dismantle the shaft and give everything a good clean. Basically the white ring clip sits over the shaft where the hole is. The small brass nipple fits into the hole, the spring goes on top and the brass collar holds everything in place. When the long thin inner brass rod is in place the nipple is in permanent contact with it regardless of rotation. The copper contact completes the circuit.



There is a series of pictures of the horn components here: http://etypeuk.com/forum/viewtopic.php? ... &start=470 As Larry says you need beryllium copper contacts rather than the pure copper ones. Hutsons sell the repair kit if you need it. This is the repro copper contact to be wary of:

[PhilBell]

Hi David

Looks like my problem may lie in the slip ring arrangement you describe. If I earth the purple and black wire that pushes into the Cu-Be connection on the column the horns work, also if I run a wire between the splined part of column and the brass push rod. So I know that all wiring, fuses and relay downstream of the column work. But operating the horn button on the steering wheel (which has the CMC quick release adaptation incidentally) or removing the wheel and manually pushing the brass rod gives no horn.

Forgive the dumb question (many late nights in the garage trying to get the car ready for its pre-Le Mans MoT is resulting in brain fade) but should I be looking at dismantling the column/push rodd assembly as in your picture, and how fiddly/time consuming is this? Also, it feels as if the brass pushrod can be withdrawn without disconnecting anything first, though I haven't pulled it out all the way for fear of creating unnecessary work/hassle.

[Heuer]

Pushing the brass rod will do nothing - you need to earth it. Basically the Growler horn push should have a metal insert so when you press the button it creates a circuit from the outer column (earth) to the brass rod. The brass rod makes moving contact with the brass tab which goes to the horns via the purple wire. Start by earthing the brass rod - if the horns sound it is the horn push assembly that is faulty. If it does not sound the horns your problem is the spring connector.

Very easy to remove the upper column. Two bolts at the top mount and a single bolt at the splined end in the footwell. You need to take off the indicator stalk and disconnect it but that is easy. You can just pull out the brass rod as it is not connected to anything other than touching the brass spring contact. Once you have the upper column on the bench you will be able to check for continuity. Probably the spring contact has moved away from the brass rod.

[PhilBell]

Thanks David

Already had the indicator off, and now that's not working. One step forward, one step back?

[PhilBell]

Hi David

Earthing the brass rod activates the horn, so I turned my attention to the horn push as you suggest but can't work out what's wrong with it ? nothing appears to be damaged or missing.

The visible end of brass rod sits in a black plastic insulator that carries the spring. Inside the back of horn push I can see a brass-coloured ring and below that an anodised metal plate that's dished at the point where it will contact the end of the brass rod. That metal plate rattles around loosely in there (always has when I've removed the steering wheel) and the action of the growler push button seems a little stiff/sticky but can be depressed.

Obviously depressing the growler brings the floating metal plate into contact with the end of the brass rod and the large metal cup that mounts the plastic part of the horn push assembly to the steering wheel boss. However, the steering wheel boss on my car is plastic so I can't work out how the mechanism can get an earth.

[Heuer]

With the CMC removable steering wheel off you should see this. Run a wire from the brass nipple to the column and the horn should sound. Make sure it continues to sound as you press the nipple all the way down against the spring.:


I dismantled this horn push so you can see what is inside (although this has a part missing). On the underside is this cup which should make permanent contact with the aluminium steering wheel hub when attached - the three grub screws grab it. :


On the inside you should have a brass ring connected to the attachment cup. The horn push itself should have a metal dished brass/copper cup glued to it - that is the part missing on this one but you can see where it was attached:


When the Growler is pressed the copper cup makes contact with the inner brass ring which is connected to the outer cup which is butted to the steering wheel boss. This is looking inside a complete horn push and you can see the brass cup:


To test put a meter probe down into the brass cup and clip another to the outer cup. Pressing the horn should give you a circuit. If not the horn push is faulty. You can dismantle the horn push if you are very careful. First remove the rubber sealing ring, gently straighten out the bent over chrome tabs and push the horn apart.

Don't understand when you say the boss is plastic. Photo?

[PhilBell]

In between wrestling with the rear hub bearing last night I just had time to examine the steering wheel boss more closely. As you suggest, it's not plastic but aluminium. I was fooled by the black anodised/painted finish.

So, the metal cup on the back of the horn push should earth via the three grub screws that secure it by passing through the boss, and that should earth to the steering column via either the splined section or the three ball bearings that lock the boss to the groove in the column.

Running a wire from the end of the brass rod to the boss or one of the grub screws doesn't sound the horn, and if I do the same with a test lamp it doesn't light up. Earthing the rod via any other earth point, including the column splines does work.

So, looks like the boss must be making poor contact with the column. Should be easy enough to check and clean up for a better connection. Of course it all looks clean and corrosion-free, but poor connections often do.

[Heuer]

As you have removable steering wheel I suggest you fit it with the horn push removed. You can then short the brass rod to various parts of the wheel to see where the problem lies. Equally with the steering wheel off the car but with the horn push attached you can test to see if the button contacts work.

[ralphr1780]

David, are you willing to part with the dismantled horn push, only the black plastic base (eventually with the metal ring/cup)? Mine (original) is broken, while the growler and chrome are in good condition. I would rather try to salvage this original one than buying a new repro.

[Heuer]

PM me your address Ralph, it is yours!

[ralphr1780]

Thanks David, I'll think of you each I will blow the horn!