bob-menhennett Posted October 27, 2012 Report Share Posted October 27, 2012 Doing a pre MOT once over and the horns are not sounding, when the horn push is pressed. Tested the horns, working OK.I've worked through the wiring ( power ) up to the ring under the steering wheel, full battery volts. Jumper continuity checked, OK.Full battery volts to top of jumper, when fitted. Earth side continuity, from the chassis earth, near the steering column up to the top where the steering wheel nut fits.So no breaks in the earth wires between the universal joints on the steering column. Horn push, continuity...none.. when button not touched...OK when button depressed. When I press the button there is a faint / half hearted attempt to connect electrically and here is the peculiar thing the ignition light comes on. I had a few earth wires on the steering column clamp bolt, which I have repositioned to a different part of the bulkhead, but..... no change. Electrics are not my strong point...( I'm learning )....so where do I look next to crack the problem please experts ? Thanks in anticipation. Bob Quote Link to post Share on other sites
RogerH Posted October 27, 2012 Report Share Posted October 27, 2012 Hi Bob, have you checked the springy thing in the steering wheel boss - the copper braid has been known to break. Roger Quote Link to post Share on other sites
AlanT Posted October 27, 2012 Report Share Posted October 27, 2012 You need two things to solve this kind of problem. 1. a test-meter of some kind 2. an understanding of how it is supposed to work Are you missing either or both of these. Al. Quote Link to post Share on other sites
AlanT Posted October 27, 2012 Report Share Posted October 27, 2012 You need two things to solve this kind of problem. 1. a test-meter of some kind 2. an understanding of how it is supposed to work Are you missing either or both of these. Al. Quote Link to post Share on other sites
bob-menhennett Posted October 27, 2012 Author Report Share Posted October 27, 2012 Roger... thanks the horn contact brush / jumper as I call it ...is fine. Al.... 1.yes ,I have a multi meter 2. some knowledge but clearly not sufficient...hence the request for help from the experts please. Bob Quote Link to post Share on other sites
wayne taylor Posted October 27, 2012 Report Share Posted October 27, 2012 Presumably you eliminated the in line fuse tucked away alongside the bottom of the inner wing? Quote Link to post Share on other sites
bob-menhennett Posted October 27, 2012 Author Report Share Posted October 27, 2012 Wayne Thanks...yes the fuse was OK and I got the horns to sound by replacing the horn button with a jumper lead. Something else is going on electrically that shouldn't but I don't have the knowledge as to what it is or where to start tracking it down logically. Bob Quote Link to post Share on other sites
MikeF Posted October 27, 2012 Report Share Posted October 27, 2012 Doing a pre MOT once over and the horns are not sounding, when the horn push is pressed. Tested the horns, working OK.I've worked through the wiring ( power ) up to the ring under the steering wheel, full battery volts. Jumper continuity checked, OK.Full battery volts to top of jumper, when fitted. Earth side continuity, from the chassis earth, near the steering column up to the top where the steering wheel nut fits.So no breaks in the earth wires between the universal joints on the steering column. Horn push, continuity...none.. when button not touched...OK when button depressed. When I press the button there is a faint / half hearted attempt to connect electrically and here is the peculiar thing the ignition light comes on. I had a few earth wires on the steering column clamp bolt, which I have repositioned to a different part of the bulkhead, but..... no change. Electrics are not my strong point...( I'm learning )....so where do I look next to crack the problem please experts ? Thanks in anticipation. Bob So the horns work if directly connected and the wiring is OK to the horn button and from the horn button. If so, using a short piece of wire or otherwise connect the live feed at the horn button to the steering column, the horn should sound. If the horns sound then the problem is in the horn button/springy post/ring connection area. Just ground one end of the wire and work your way along the chain of components until the horn doesn’t sound. That will identify the culprit. Irrespective of which it is you might like to clean everything up and get them tickety boo whilst in there, you don’t want to come back later. The ignition light coming on is a little bit of a puzzler, possibly concern. The horn circuit as originally wired does not go through the ignition; it is a completely separate circuit with its own fuse. This indicates the possibility of a frayed or shorting wire somewhere, or possibly a poor earth connection somewhere also. A multimeter is quite handy at identifying “live” wires” but doesn’t really test the quality of a circuit (its connections). Personally I prefer to use a brake light bulb (20 watts or so). With good connections it will light brightly. With a poor connection/bad earth, a multimeter can show 12 V the bulb will light but not as brightly under those conditions. Mike Quote Link to post Share on other sites
tthomson Posted October 27, 2012 Report Share Posted October 27, 2012 Hi Bob, You don't say whether you have a TR4 or a TR4A The horn circuit in the TR4 does not have a relay, while the TR4A does. If this relay is present it is normally located close to the offside horn (RHD) On the TR4, the horn button handles quite a large current and if the brass ring is not really clean, you can get a problem with the horn being intermittent Using a relay removes this high current from the button, and puts it through the relay instead. For any circuit taking a large current (like the horns) make sure all the intervening connections are clean as possible. The ignition lamp problem indicates a high current draw, but without looking at the car itself, it is not really possible to identify what is going on. Good luck with it. TT Quote Link to post Share on other sites
bob-menhennett Posted October 28, 2012 Author Report Share Posted October 28, 2012 Mike and Tony, I am very grateful for your input.... I shall continue to track down the problem and try out your suggestions. Bob Quote Link to post Share on other sites
AlanT Posted October 28, 2012 Report Share Posted October 28, 2012 My ordinary Lucas horns were measured as taking 8.5A. People are often adding relays to these cars but the only place I would think this is essential is this horn-circuit. This is because there are so many points a which it is difficult to maintain a low-resistance connection. Especially dodgy is earthing the column via the pinion at the bottom. The relay coil will only need maybe 1A so you can now tolerate a lot more resistance in the circuit before it will stop. If your test-meter can measure up to 10A use the current range to complete the circuit where the horn-push should be. I you dont have a relay you will need to get something like 8A. Al. Quote Link to post Share on other sites
bob-menhennett Posted October 30, 2012 Author Report Share Posted October 30, 2012 Update. The high note horn was obviously in it's death throws and was prounounced "dead " when I restarted checking everything again from scratch. Horn replaced, MOT.... passed with no advisories !! However I still have the ignition light saga but at least I can tackled that methodically in my own time, without the MOT hanging over me. Thanks again guys. Bob Quote Link to post Share on other sites
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.