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Spitfire 1500 horn


Kiajon
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Hi there people. I hope you are all well.

My pageant blue W reg spitfire that you so graciously helped get back on the road last summer is coming up for its MOT. The problem is I’ve lost my horn! It was intermittent for a while (due to a loose wire) and now it has totally gone. 
I ordered and have fitted a new indicator stalk supplied by Rimmers which does everything else but still no horn. I then looked at the wiring and there appears to a missing wire in the connecting block of the new switch. A purple one! 
What can I do? Is there an alternative way of wiring the horn to say a push button on the dash or a centre push on a steering wheel.

Your advice as always will be gratefully received! 
 

Cheers

Jonathan

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do you have a horn relay ???  on the  baulkhead

well most would run a purple to the horn relay (ive not checked the wiring plan) as the main feed the relay would be earthed via the slip ring , the pencil in the handwheel and earthed with a wire across the column UJ and the rack earthed to the engine front plate 

there is not generally a purple feed to the column /stalk area  only an earth 

on non relayed horns the horn has the live feed and the earth runs from the horn to the column slip ring then follows above 

Pete

 

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Jonathon,

I didn't think Spitfires had a horn relay which is why your new stalk doesn't have a purple wire? I would suspect a connection problem nearer the horns, do they work directly wired to the battery?

Doug

 

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My 1300 spit has a horn relay, maybe it shouldn't. Had a problem when recomissioning the car a few years ago. Even when connecting the units directly to the battery one sounded like a strangled cat. Finally managed to find that the culprit was crud on the contacts. Mine also had adjusters on the horn case which were also crudded up. You can strip down the horn units, I have done it. Inside they are very simple. I have photos somewhere. Drill out the rivets and replace with suitable bolts. Fiddly, but worth the effort.

Have a look here..

https://forum.tssc.org.uk/topic/2580-horn-unit-faulty/?tab=comments#comment-23941

..there may be something that might help.

 

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My 1975 Spitfire 1500 has a relay which is live and actuated by pressing the steering wheel centre which earths the relay coil outlet.  I have checked the later wiring diagram for the stalk actuated models and they too have the same relay.  It is a special (expensive) relay with only three connectors but you can use a standard four pin device by connecting the two power in connectors together.  When the relay is actuated, 12 volts is fed to the two horns which have earth connections to the chassis.

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Thanks for the suggestions. I’ll go through your check lists over the next couple of days and then get back to you! If there is a relay where will I find it? 
 

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According to the Haynes wiring diagram the late 1500 spit did not have a relay (all others did) the switch should have a purple wire going in and a purple/black going to the horns. I would try running a test wire from the purole in the block to the purple/black and see if the horns sound, if it does it is the switch if not the problem is likely elsewhere. this is very different from the earlier wheel centre push where the switch is in the earth from the relay

Yo could use a separate switch somewhere but far better to get it working properly.

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Interesting that the Haynes wiring diagram does not show a relay but the owners handbook does show a relay.  If a relay is present it is near the ignition coil.

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9 hours ago, GrahamB said:

Interesting that the Haynes wiring diagram does not show a relay but the owners handbook does show a relay.  If a relay is present it is near the ignition coil.

did they just not update the owners manual, my 1966 spit owners manual still refers to the older style door arrangement and most of the photos are actually from a mk1 of course Haynes could be wrong!

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Quick update. The horn works when current run across it. Now to check the wiring by doing the trick DanMi has suggested! If there's a loud band heard over the Midlands you'll know I got it wrong!!! 😉

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if you have a multimeter or 12v test lamp test for power on the purple in the block, if there is no power then follow the purple back to the fusebox checking for power as you go. If there is power then check the resistance between the purple and black and earth, there should be a bit from the horns but if open circuit then you need to follow that wire to find a fault all the way to the earths from the horns. I am assuming that the Haynes manual wiring diagram is correct as I haven't worke on late spit switchgear

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  • 3 weeks later...

So the red lead on the purple wire and the black on a good earth point. Ign on or off? Does that make a difference? Or disconnect battery and start at the horn and use resistance through the cables back . There should be resistance through the horn but not open circuit. If open circuit it would suggest the horn is faulty. The only other open circuit will be the switch and when pressed will have a low resistance figure. Keep going until open circuit is found. You could try half split method to save time instead of from one end to another.

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Cheers Matthew. Ignition off but also the same with ignition on. The horn works when wired directly to the battery (scared the hell out of my 2 year old daughter!) Electrics are a dark art to me. Learning as quick as I can though! 

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Ok, fuse tested for resistance. The wonderfull thing about electrics and all fault finding is the amount of other bits you find wrong that are not even part of the initial problem! No end of jobs you go finding a fault where amazing they seemed fine before! Thats where the dogged sticking to tracing the fault and not being diverted. Are you going to the show this weekend? As i would not mind going through it with you as i find it easier to show than to explain! As you say the horn works, so you are looking for the brake in the flow of electricity. Follow it up stream till you find where that break is. There are methods to speed the process up but that one will get you there! A good split point is the switch. Power at the switch? If no Follow to the fuse if yes check flow after and to the horn could save time.

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48 minutes ago, Mathew said:

Ok, fuse tested for resistance. The wonderfull thing about electrics and all fault finding is the amount of other bits you find wrong that are not even part of the initial problem! No end of jobs you go finding a fault where amazing they seemed fine before! Thats where the dogged sticking to tracing the fault and not being diverted. Are you going to the show this weekend? As i would not mind going through it with you as i find it easier to show than to explain! As you say the horn works, so you are looking for the brake in the flow of electricity. Follow it up stream till you find where that break is. There are methods to speed the process up but that one will get you there! A good split point is the switch. Power at the switch? If no Follow to the fuse if yes check flow after and to the horn could save time.

Thanks for the guidance. Unfortunately I'm working at the weekend so can't make the show. 

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With my test light and multimeter in hand I started probing and found that there was no power getting to the switch! Nothing across the middle fuse… that’s a problem I’ll deal with later….. so I’ve plumbed it into a different power wire and hey presto the horn is working. So now I can go and get it MOTd and then have a look at the wiring on a rainy day! 
The fuse box seems a little tired…. is changing it or upgrading it a big job? 

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the fuse box is the weak link each fuse end cap links the two fuse box blades to feed other circuits , so the cap not only feeds the fuse wire in it 

it also bridges the fuse contacts any corrosion or weak springy will fail a circuit that is not actually fused  

replacing with  a modern unit is covered on here if you use the search box 

but a good clean and a light reform of the blades to make a firm cap contact can revive a  tired fuse box for now .

Pete

 

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1 hour ago, Pete Lewis said:

a light reform of the blades to make a firm cap contact can revive a  tired fuse box

... or even a brand new one! They're not a very good design. I ended up adding a bit of self-adhesive springy foam behind the fuses to get decent reliable contact on the one fitted to a brand new loom.

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