Steering wheel earth

[jreacock]

And another wiring question... Does anyone know how the steering wheel is earthed?

I've been chasing down a problem with the horn on my Spyder for a while now. I spent a long time verifying the connections to the horn relay, checked everything against a spare fuse box, checking voltages and continuity and found nothing wrong. Everything seemed to be as it should, but no horn. I could make the horn sound by removing the cover off the relay, and pressing the contacts by hand - so I knew the horn wiring part was ok. The 12V went through the relay coil and on up to the steering wheel, and I verified that the 12V got to the top slip-ring part of the wheel through the sprung copper contact. The problem - as far as I can see, is that the steering wheel isn't earthed in any way (the centre part that the securing nut screws on to), so when the horn is pressed, the 12V circuit from the horn relay coil is not being grounded and made a complete circuit - it still floats at 12V. If I manually ground the 12V line that feeds the copper contact, then the relay works.

So - I wonder how this upper part of the wheel is earthed. I can't find anything that earths it - it's secured in plastic bushes, and because it rotates, it's difficult to do much about it. It joins a UJ, the top part of which has continuity with the top splined part, but the lower half of the same UJ that then goes down to the bottom UJ (and then out to the steering rack) has no continuity.

Does anyone know how the steering wheel centre splined boss is earthed?

I've spent many hours on this now - and although I've found the reason for the issue - I'm now not sure how to solve it. I've not disturbed the wheel at all, so I don't know why this stopped - but I notice that I've circled the horn relay in the Haynes manual, so I think I must have had problems in the past with this.

Thanks for any help.

Cheers,
Justin.

[HFStuart]

I'd always assumed it was earthed via the steering rack earth lead. It's a tab near the rack damper on manual steering cars. It should have an earth lead on it.

[jreacock]

Hi Stuart. Yes - I've noticed that earth tab. Mine doesn't have a connection at the moment. I noticed it, but didn't think it could be that - only because the splined part doesn't seem to be connected to anything (continuity-wise) any further down the rack than the first universal joint - but it's definitely worth a try. I've almost spent as long on this issue as I did building the engine back up. It's getting ridiculous.
Thanks for the suggestion.

[jreacock]

The steering rack earth tab being earthed didn't fix this. What I've had to do in order to get the horn to work, is to connect the top universal joint to the lower one with a wire that wraps around the shaft. It all rotates together and the connection is maintained. I used a solder tab as a washer on each of the 2 clamps that secure the shaft to the splined parts of the steering column. Now - the horn works. I guess that something must be missing in order for this to have been a problem.

[lukasdeopalenica]

Apart from that, at least mine, has also an earthing lead (black) connected to the bottom part of steering column's not moveable part (outer section). It is hidden by the plastic housing.

[jreacock]

I would have thought that outside and inside parts of the steering wheel assembly would be connected, but seemingly not. I think that my upper steering shaft must have some high resistance residue that has effectively disconnected (with respect to electrical continuity) the 2 parts of the universal joint. It's hard to believe, as it's an all metal assembly - but the lower part of the top most UJ is earthed, and the top part of the same joint isn't. I plan to remove the steering rack upper part today, to correct a rotational offset that I have after refitting the rack ages ago. I thought I could do this by just rotating the st. wheel - but it has a locating spline. Removing the main rack isn't an option now (that the engine is back in), so I think I can split the top UJ and take the top part of the wheel assembly off. I'm hoping that disturbing the UJ might shed some light onto the issue that I've had.
Thanks to all for replying.