63 FHC - horns not getting enough power?

Technical advice Q&A

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rswaffie
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#1 63 FHC - horns not getting enough power?

Post by rswaffie » Sun May 13, 2018 2:37 pm

Hi All,
I’ve been testing the new wiring out as part of the restoration and have connected up the original horn relay and have removed the p/y wire from it and connected up each horn to it to test, both singly and together however, I’m not getting the tuneful notes I was hoping for...





Although the relay clicks, does this suggest a defunct relay?
Richard

S1 3.8 FHC Opalescent Golden Sand 889504
Undergoing a comprehensive restoration in my small, but utilitarian garage :wrench: :hammer: :fingerscrossed:

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cactusman
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#2 Re: 63 FHC - horns not getting enough power?

Post by cactusman » Sun May 13, 2018 3:30 pm

Horns do draw a very high current hence the relay and the 50 amp fuse in the feed. I'd pop in some ear plugs and run them direct from the battery to check they do indeed work and the earths from the horns are good. Use some thick cable.
If they work with a direct feed then measure the voltage at the horns with them operating from the usual feed. You wont see 12 volts but less than 9 or 10 and they may be a bit feeble. Check the fuse holder feeding them is clean..fuse no 3. Try a new relay.
Julian the E-type man
1962 FHC
1966 MGB....fab little car too

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rswaffie
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#3 Re: 63 FHC - horns not getting enough power?

Post by rswaffie » Sun May 13, 2018 5:14 pm

Thanks Julian,
I have swapped the relay, but still no joy. I’ll have to charge up the battery to do a direct test - I’ve been using a DC transformer set to 12v for the testing so far, which has been fine for all the other components. I’m getting just under 12v at the horn when pressing the centre push.
I’ll have another crack tomorrow.

Cheers,
Richard

S1 3.8 FHC Opalescent Golden Sand 889504
Undergoing a comprehensive restoration in my small, but utilitarian garage :wrench: :hammer: :fingerscrossed:

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mgcjag
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#4 Re: 63 FHC - horns not getting enough power?

Post by mgcjag » Sun May 13, 2018 6:02 pm

Hi Richard...there should also be an adjuster on them that you need to use to tune them in as you have them vibrating.... Steve
Steve
1969 S2 2+2 & Building a C type replica

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cactusman
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#5 Re: 63 FHC - horns not getting enough power?

Post by cactusman » Sun May 13, 2018 6:33 pm

Good tip from Steve. Do be aware though that they present a very electrically unpleasant load, a pulsed load where the current peaks will be well over 15 amps. Unless you have a substantial power supply it is unlikely to cope. Any with electronic current limiting will limit the current and if this limit is less than about 15 amps (few power supplies will have this capability), your horns will sound poor. Use a charged car battery unless you have a very substantial power supply.
Julian the E-type man
1962 FHC
1966 MGB....fab little car too

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christopher storey
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#6 Re: 63 FHC - horns not getting enough power?

Post by christopher storey » Mon May 14, 2018 8:23 am

They sound a minor third apart to me, which is what was designed I think ! As others have said , you will never get a proper sound from a DC supply such as a battery charger. I would stick them on the car and then run them when proper battery power is available

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rswaffie
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#7 Re: 63 FHC - horns not getting enough power?

Post by rswaffie » Mon May 14, 2018 9:31 am

Thanks all.

Hooking up the battery will be the next step. I guess I should be happy that the wiring through to the relay all seems ok and that the steering column/horn push connections are good!
Richard

S1 3.8 FHC Opalescent Golden Sand 889504
Undergoing a comprehensive restoration in my small, but utilitarian garage :wrench: :hammer: :fingerscrossed:

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#8 Re: 63 FHC - horns not getting enough power?

Post by rswaffie » Mon May 14, 2018 8:41 pm

I hooked the horns up to a battery booster.
They work perfectly.
I should get my hearing back in a day or so :seeingstars:
Richard

S1 3.8 FHC Opalescent Golden Sand 889504
Undergoing a comprehensive restoration in my small, but utilitarian garage :wrench: :hammer: :fingerscrossed:

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