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MG Midget and Sprite Technical - Horn dilemmas
|On the horns of a dilemma re Frogeye horns, though it probably applies to other cars too.
First,why the odd wiring? Run a permanent live all the way to the very front of the car and then all the way back again and operate it by earthing it at the steering wheel. So there is a much longer wire than necessary, permanently live and just waiting to chafe through. Why not earth the horn and run a single switchable wire from the horn that only goes live when operated.
Seems much simpler and safer to me!
Why is the horn always on, and not controlled by the switched live, as are wipers and heater? The only practical benefit I can think of is for an impatient driver, sitting with the engine switched off, waiting for his date to finish checking her hair before coming out. But tooting the horn isn't going to win him any favours tonight, that's for sure!
Wiring my horn, as per Workshop Manual, it didn't work. Investigation quickly showed up that the steering column isn't actually earthed. This surprised me as all the bits are clamped and bolted together, seemingly giving a continuous chain of metal components via steering column, pinchbolt, rack, clamps and various bolts direct to the chassis. But it isn't because touching a short jump lead from pinch bolt to a chassis point makes the horn blare. Long winded way of asking what is the normal way of ensuring the column is earthed on a Frogeye?
|If it is the same as the mark III, the column is earthed by a short braid from the lower rack mounting bolt to one of the bolts on the rack pinion thrust plate.|
|One reason for not having the horn powered through the ignition switch would be to reduce the current through the switch itself. |
Also, its a lot easier to switch to earth when the switch is on the steering wheel. Switching live would necessitate two connections from column to horn push.
Late model midgets and MGBs did switch the live feed to the horns, but the switch was on the stalk by then.
|Dave O'Neill 2|
|I had the exact problem, I couldnít see how it wasnít earthed. So I just jammed a bit of wire in the gap between the rack and the alloy clamp - as a temporary measure (but itís still there!). Iíll make up a lead as Bill describes.|
|Dave, I do see and agree your second point. |
Not convinced though, that the current through the switch contact is any less on the earthing side. It completes the circuit, wherever it is and the current flowing will be the same.
|John, it seems those little packing pieces around the rack clamps must be providing the insulation then. Quite surprising that there isn't some metal to metal contact though.|
No suggestions yet as to why the horns aren't on the switched live circuit, like other ancillaries?
|Don't Dave mean the ignition switch.|
|Ah, yes. I get it now. Thanks Nigel. Sorry Dave!|
|mine seems to earth ok without any additional wiring so it must be getting it from the rack supports. On looking the sides of the rack touch the rack supports sufficiently. If I recall were horns, back in the day, not meant to sound an audible warning without the ignition being switched on??|
|I think the steering boss end of the circuit is earth because, if it was "live", there's a chance of an inadvertent short to earth from the slip ring.|
This thread was discussed on 25/05/2020
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