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Morris 8 wiring gremlins
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Bob T



Joined: 16 Nov 2010
Posts: 128
Location: Sudbury, Suffolk

PostPosted: Mon Apr 11, 2011 8:31 pm    Post subject: Morris 8 wiring gremlins Reply with quote

HI, I am coming to the end of a restoration of a Series 1 Morris 8, the car is 6v negative earth.
When I first wired up the engine/ignition nothing worked and I discovered that both leads on the dizzy were live !! by process of elimination I cleaned off my nice new paint where the battery earth strap goes on to the bulkhead and all was well.
Today I have rewired the indicator/horn/dip swithch. The semaphores work fine but the horn does not. I discovered a duff fuse in the control box which replaced but still no joy, except that now both leads to the horn are live !!
So remembering my previous experience I earthed the body of the horn direct to the chassis expecting it to then work..........nothing.

Can anyone offer any advice? I guess I am going to have similar problems when I put the lights back on as the whole car has been reppainted from bare metal.

My knowledge of electrics is basic so some help would be appreciated.
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peter scott



Joined: 18 Dec 2007
Posts: 7113
Location: Edinburgh

PostPosted: Mon Apr 11, 2011 9:33 pm    Post subject: Reply with quote

Try connecting the horn directly across the battery terminals. If they haven't been used for a long time then the contacts can get a bit high resistance and the horn needs lots of current.

If it doesn't work then remove the cover and just try pressing the contacts together whilst the horn is connected to the battery. If it then sounds then the arcing will probably clean the contacts for you.

If the horn does operate then you just need to progressively bypass parts of the wiring to and from the horn button. The horn button contacts can also need cleaned.
Check that the steering column is properly earthed too. The trafficators do draw a fair current but nothing like as much as the horn.

I think that both horn connections should normally be live and only when you press the button should the horn have both positive and negative on its terminals. (The button connects the chassis to the horn.)

HTH

Peter
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http://www.nostalgiatech.co.uk
1939 SS Jaguar 2 1/2 litre saloon
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Bob T



Joined: 16 Nov 2010
Posts: 128
Location: Sudbury, Suffolk

PostPosted: Mon Apr 11, 2011 10:35 pm    Post subject: Reply with quote

peter scott wrote:
Try connecting the horn directly across the battery terminals. If they haven't been used for a long time then the contacts can get a bit high resistance and the horn needs lots of current.

If it doesn't work then remove the cover and just try pressing the contacts together whilst the horn is connected to the battery. If it then sounds then the arcing will probably clean the contacts for you.

If the horn does operate then you just need to progressively bypass parts of the wiring to and from the horn button. The horn button contacts can also need cleaned.
Check that the steering column is properly earthed too. The trafficators do draw a fair current but nothing like as much as the horn.

I think that both horn connections should normally be live and only when you press the button should the horn have both positive and negative on its terminals. (The button connects the chassis to the horn.)

HTH

Peter


Thanks for the info Peter, I will give it a try, I have already wired the horn direct and it does work, so maybe the earth issue is the problem.
Cheers
Bob
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peter scott



Joined: 18 Dec 2007
Posts: 7113
Location: Edinburgh

PostPosted: Mon Apr 11, 2011 11:04 pm    Post subject: Reply with quote

Hi Bob,

Given that the horn works you can test both positive (live in your case) and earth. Put your test meter or a 6 volt bulb between one of the horn terminals and chassis earth. Then get a helper to press the horn button. One of the horn terminals should go to earth potential (ie no meter reading or bulb not lit). Then do the same test with your meter or bulb between the other horn terminal and earth.

Given that your horn doesn't work I would expect that the meter or bulb will either show 6 volts on both horn terminals (in which case the wiring to and from your horn button is not connecting) or the meter or bulb will show 0 volts on both horn terminals when the button is pressed (in which case there is a bad connection between your battery positive and the horn.

Peter
_________________
http://www.nostalgiatech.co.uk
1939 SS Jaguar 2 1/2 litre saloon
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Bob T



Joined: 16 Nov 2010
Posts: 128
Location: Sudbury, Suffolk

PostPosted: Tue Apr 12, 2011 8:33 am    Post subject: Reply with quote

peter scott wrote:
Hi Bob,

Given that the horn works you can test both positive (live in your case) and earth. Put your test meter or a 6 volt bulb between one of the horn terminals and chassis earth. Then get a helper to press the horn button. One of the horn terminals should go to earth potential (ie no meter reading or bulb not lit). Then do the same test with your meter or bulb between the other horn terminal and earth.

Given that your horn doesn't work I would expect that the meter or bulb will either show 6 volts on both horn terminals (in which case the wiring to and from your horn button is not connecting) or the meter or bulb will show 0 volts on both horn terminals when the button is pressed (in which case there is a bad connection between your battery positive and the horn.

Peter


Thanks for the update, even I can understand your instructions. I will try when I get home from work later.
Regards
Bob
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Peter_L



Joined: 10 Apr 2008
Posts: 2680
Location: New Brunswick. Canada.

PostPosted: Tue Apr 12, 2011 3:55 pm    Post subject: Reply with quote

Isn't the battery supply made directly to the horn and the earth goes via the horn button ? removing the need for a cable passing along the steering column. ? Two connections on the horn neither of which goes to the external horn body.
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Bob T



Joined: 16 Nov 2010
Posts: 128
Location: Sudbury, Suffolk

PostPosted: Tue Apr 12, 2011 4:47 pm    Post subject: Reply with quote

Thanks for all the advice, I cleaned up the switch and took some paint off the steering column where the stalk bolts on and it all works !!

Lights next, then an MOT !!
Cheers
Bob
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