Lotus Elan and Lotus Elan Plus 2 Forums

Hi
I recently bought a 1972 Sprint where the electrics in the engine bay had been renewed badly. The connections to the air horn compressor have, for some reason, been by-passed. Can someone help me with the original wiring?
Thanks for the help
John

Just wanted to add that what I am really looking for are the colours of the wires that originally powered the horn compressor. Thanks

John,

I only have a S4 wiring diagram, I haven't seen one specifically for the Sprint - although one possibly may exist.

The wiring diagram in the manual is difficult to read and the horn wiring is not clear - the air horn compressor doesn't appear and there is an associated relay shown as 'optional' with unmarked wires going to it.

The wires that can be identified as going to the horns are PB - purple and black, this goes to the horn button in the centre of the steering wheel, and P - purple which goes to the fusebox for the power feed.

My Sprint's wiring was dreadful, I have replaced much of the wiring to the relays and the colours aren't original I am afraid. If you don't have a horn relay, you will need one as the compressor draws a lot of current.

Andy.

Andy

That's really useful. I have a number of purple wires - one in fact goes nowhere so I suspect that's the orginal air compressor unit one. There seems to be a relay present with a purple wire connection so I'll start there.

Glad to hear that mine is not the only one with crazy wiring.

Thanks
John

Hi John,
Like Andy I only have the S4 diagram but mine does show the compressor. The current draw is quite high so you may want to add an additional feed to the relay from the fuse box and just use the original horn feed to switch the relay.

oldelanman wrote:Hi John,
Like Andy I only have the S4 diagram but mine does show the compressor. The current draw is quite high so you may want to add an additional feed to the relay from the fuse box and just use the original horn feed to switch the relay.

Air Horn Wiring.jpg

John,

I have the same wiring diagram as Oldelanman, but nowhere near as clear. The 'Horn comp when fitted' on mine is just a splodge. The manual came with my car. I was told it was genuine Lotus, but I suspect it is a dodgy photocopy.

Even Oldelanman's much clearer wiring diagram doesn't give much away when it comes to the wiring of the relay. If you need more help, post the details of your relay when you have figured out which one you want to use, and I can help with the connections.

Andy.

Thanks all
I will do a bit fidling and probably by trial and error work out what goes where. I'll post the results in due course (got the c head to re-install at the moment)
Cheers
John

as long as there is darkness! I would need an understandable and clear wiring diagram for the S3 well detailed for my eyes so if we can see it!

Hi Geni,
I can send you a wiring diagram for the S3 if you want.
I get several copies printed at A3 size by the local print shop and highlight the circuit I am working on.
I am told it is still quite readable at A2 size.
If you send me your email address by PM, I will send it. Don`t put emails on this open forum.
Eric in Burnley
S3SE DHC

The plot thickens. I've just found a "separate horn button" fixed to the underside of the dashboard. I'm guessing the previous "master electrician" couldn't work out how to connect the horn push on the steering wheel. I can't believe its that difficult, is it? Attached photos of what I have.
Grateful for the assistance restoring the system.
Thanks

The wheel switch works by bridge the ring shown with the steering column that is grounded.

The standard wheel/hub used a spring loaded "pencil" to contact the ring and run to switch input. The switch then grounds via the hub/column. After market may have a different setup.

The other common issue is broken/missing bridge cable that the steering column flex joint near there rack. This can break the earth connection on the column and so the horn working.

Thanks for that - got it. The bridge cable is missing so my guess is that's why the horn was re-routed. Do you know what colour wire feeds the ring?
Cheers

Mrozik wrote:Thanks for that - got it. The bridge cable is missing so my guess is that's why the horn was re-routed. Do you know what colour wire feeds the ring?
Cheers

In addition to the bridge wire across the column flexible coupling the rack itself should be earthed....



The feed wire to the horn slip ring should be Purple/Black.

You should find three bullet connectors joining the column switches and horn push to the main loom ...here's how my S4 column wiring is connected ... note the mismatch of wiring colours for the dipswitch.

Many thanks. That's exactly what I needed.