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Lotus Elan Sprint


David6

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Hello all.

I have a 1970 Elan Sprint DHC. Negative earth with Dynamo.

I'm Fighting to get the horn working. With the horn off and 12 volts across the terminals it works fine.

It was my understanding but I might be wrong, with the ignition on then the horn always has a positive feed to it and that when pressing the horn it put a negative earth to it.

I cannot get an earth at the top of the steering column anywhere and I was then thinking I need to find out where the column gets it's earth from. However I now find that one of the wires going to the horn is a good earth so I guess my thinking is wrong.

I get 12 volts on the multimeter from earth to the fuses so that's fine.

When I go between earth on the chassis and the other wire that goes to the horn I get 0.11 Volts so presumably there is some resistance somewhere, maybe a relay ?

I'm determined to resolve it. Any ideas ?

David

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  • 2 weeks later...

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@David6

Ok its a bit like this. 

+12vdc from the fuse to the horns, the return wire ends up in a double bullet connector under the dash. One wire runs off to the anti theft s/w and the other runs up into the steering column and connects to a brass ring at the top of the steering column. This is connected to the horn push by a “horn pencil”. When the horn is pushed the +12vdc goes from the brass ring, up the pencil, through the horn push to ground.

Id check the upper part of the column for good connections. The column is earthEd at the bottom where it enters the rack. There is usually a jumper wire between the UJ joint if it is one of the plastic ones. But I guess your issue will be in the horn push. 

As a test set your meter to ohms and connect between the column in the engine compartment and the chassis, you should see a short circuit (zero ohms). Now remove the plastic indicator stalk covers and measure the resistance between the column in the engine bay and the column near the steering wheel as you can now get to it. Again this should be zero ohms. If good then you need to remove the horn switch, remove the pencil (cant remember if you can or cant). Now carefully measure to see if you have 12vdc between the brass ring and earth. If so either pencil or horn push is fubar.

 

hope that helps 👍

Try Lotus Elan.net (electrical section) for more help

cheers

Mark

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  • 5 months later...

Many thanks for that. It turned out to be a fracture in the bridging wire over the flexible coupling at the bottom of the column. Not easy to get at but with the rad out I sorted it.

However !!

It just gave up again today and again I have a good earth at the bottom but not at the top so again it looks like a similar problem despite making sure I used a very flexible piece of wire and good end connections. This time I think I have a bigger problem. If I take a negative feed off the battery earth an touch it to the output side of the horn button I would have expected the horn to work but it did'nt.

I see you make reference to the anti theft device which takes one of the wires to the horn push and I'm now wondering if this is the other part of the problem. I can see it on the wiring diagram but where is it physically and what does it look like ?

 

David

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20 hours ago, David6 said:

Many thanks for that. It turned out to be a fracture in the bridging wire over the flexible coupling at the bottom of the column. Not easy to get at but with the rad out I sorted it.

However !!

It just gave up again today and again I have a good earth at the bottom but not at the top so again it looks like a similar problem despite making sure I used a very flexible piece of wire and good end connections. This time I think I have a bigger problem. If I take a negative feed off the battery earth an touch it to the output side of the horn button I would have expected the horn to work but it did'nt.

I see you make reference to the anti theft device which takes one of the wires to the horn push and I'm now wondering if this is the other part of the problem. I can see it on the wiring diagram but where is it physically and what does it look like ?

 

David

The anti theft switch is located in a secret position, cant tell you. 😂😂😂😂😂😂

its in the glove box, lower right hand side...

I'd check the "pencil" is making a good contact with the brass ring.....

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Found it, no wonder I never spotted that !

I only got this last September and it's certainly not as easy to work on as my MGB. Lets just say every job is a challenge.

My first few months were spent stripping and servicing the brakes and getting an operational handbrake. I got a company to make up some bowden cables to replace those crazy rods and with adjusters at both ends I have an excellent handbrake If only I could reach the handle with a seat belt on. It's still great fun however.

I hate oil leaks, and I think iv'e given up  at the moment trying to stop them ( maybe an engine out job next winter)

I'm slowly working through the electrics as the previous owner has played around with certain things making following the wiring diagram difficult to use. It would appear the handbrake warning light has not been wired through the ignition circuit so it remains on if the handbrake is on. Fortunately an isolator switch has been fitted.

I'm sure I'll find more anomalies.

Thanks again for your help.

 

David

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  • 3 weeks later...

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