Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) 3.7 Roadster

Yesterday I discovered the horn(s) weren't working on my 3.7 Roadster. I have now removed the horn push in the centre of the MotoLita steering wheel - cleaned up the copper contact strip and tested the circuit when the button is pressed in, which is all working. I have also removed the 2 horns, cleaned up the connectors and tested each one individually - both working fine.

When the engine is running they work as they should, however if I have the ignition on, but no engine running, they don't work. I can hear them trying to make a sound, but not properly. Are the horns meant to work with just the ignition on?

I suspect there may be a corroded earth somewhere? I can see on the Roadster circuit diagram that there is a wire that comes off the junction of the horn wiring to a chassis earth with a 5mm eyelet, but I can't locate it. I have tried tracing the wiring from the horns right back to the fuse box, with no luck. Does anyone know where this earth is located?

Thanks in anticipation.

Seems that the voltage getting to your horns is not enough with just the ign switched on, but rises when the engine is running and the alternator is providing charge enough to make the horns sound as they should... If the battery can spin the starter motor enough to fire up the engine, then it seems it should be capable of sounding the horns too, which then perhaps points to a relay, assuming one might be fitted in your horn circuit...? Fortunately other than for an MOT, the only time you really need a horn is when the engine is running...
Wishing you all the best in finding a quick answer to that one...

You don't currently have a problem with horn electrics Les. The horns are wired via the auxiliary position of ignition switch (first click from off) which also controls the main radio feed. Consequently it's entirely normal for the horns not to work with ignition switch in off position.

Edit: Apologies Les just re-read your post. If the battery is good enough to start the car it should be more than good enough to operate horns. Worth trying in the auxiliary position first though to see if that works without ignition switch loads. As Jon suggests try cleaning fuse 6 contacts which also carry main radio feed.

FWIW I fitted air horns requiring a relay to reduce current through horn contacts. For simplicity I used the same fuse 6 supply though having uprated it to 20 amp. It's worked fine for seven years and I'm still on original 2018 battery. Will be renewed before coming winter though.

Les, my 3.7 horns work with Ign on & as you say you can hear them trying - but they work with engine running this looks like a low voltage issue, pull and clean fuse 6 as it's an easy check to tick off

However, is your battery on it's way out, how old is it ? and have you checked the standing voltage (not on charge)

Another thought Les is the switched ground to the horns. As you likely already know this is carried on the purple/black wire to complete circuit to horns.



The connection through to the steering wheel slip ring is via the brass slip ring contact shown above secured by small screw. This is part of a brass strip that clips to a spade connector on back of light switch module which in turn gets its connection through the main seven pin light switch connector where you will see the purple/black wire running into the loom and on to both horns. It may be worth checking integrity of these various connections therefore, especially if light switch is ever replaced as this contact can be disturbed. The actual ground connection you enquired of is the steering column itself connecting via spring retaining clips on metal body of horn push when pushed back in to steering wheel boss centre, noting there is a short lead with female spade connector to the slip ring that needs to be detached for complete horn push removal. This on my MotoLita wheel and something similar with factory padded wheel.

A quick test with steering wheel removed is to switch key to auxiliary or ignition on position and hold a short piece of wire against any chassis point whilst dabbing other end on brass slip ring pickup and seeing if horns sound.

Thanks for all the replies and suggestions.

Re not working with the ignition - I don't expect them to work when the ignition is off, but I was trying to establish whether any of your cars have working horns with the ignition on but no engine running. Maybe the horns only work when the engine is running (which is probably the only scenario you would need them to work)? But strange that they try to work by making a weak noise when ignition is on and no engine running.

Having already removed the horn push, cleaned the copper strip (which from what Richard V6 said is the earth) and checked with a militmeter that it is working OK, plus having cleaned and checked the connectors to the horns, I think the next step is to remove the steering wheel and check the brass slip ring and the connectors/wiring from the light switch (purple/black) as RichardV6 suggests.

The battery was new last year and is regularly connected to my battery optimiser, so should be OK. The number 6 fuse is OK (although replaced to be sure) and connections clean.

To be clear the horns should most definately work with engine not running providing key is in auxiliary or ignition on position.

The slip ring pickup brass strip connection to light switch is difficult to describe but have found this image showing in two aspects the rear of column switch housing.



The two light switch connector receptacles can be seen on the right of upper image. You can also see the slip ring brass strip male spade connector in two aspects, adjacent to lower right hand screw. When removing light switch the matching female brass strip connection should be carefully slid off and brass strip removed before light switch can be slid out sideways (after removing two securing screws). I mention this because a high resistance connection at any of the five connection points in this area could individually or collectively cause enough volt drop to present your issue.

Been out for a run today and the horn is now working fine. As I am unlikely to use the horn with just the ignition on I am going to leave it there.

Thanks for all the great help.

Les, just remembered a friends 3.7 I did some work on a few years ago had intermittent horn issues

Turned out they were very corroded internally and I concluded the extra umph of the alternator running was enough to force them to work

Which is why mine were quickly replaced by Nauitilus Stebel air horns. Two horns and compressor integrated into one unit.



Having said that my original pair are now doing sterling service mounted high up out of the crud on my Series Land Rover.