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MG MGB Technical - Horn Relay

The new Hella horns(hooters)recently purchased contain a relay, is this relay necessary for fitment to my MGB?
t burnett

Hard to say without a data sheet. Horns are usually around 1 to 2 ohms so probably you can avoid the relay, but its so easy to fit why not use it? Decades ago wnen I put the Maserati air horns on my car they came with a realy to drive the compressor. My car has a live horn switched earth circuit, so you put the coil where the horn was and take the 12v across to the horns via the relay contacts and provide an earth.
Stan Best

On my '69 B the horn push earths the circuit. But the steering column is not well earthed (well not on my car). As a result not enough current is passed to power two horns directly and they only squawk, but it works fine through a relay. If you've got a relay I would use it and save the contacts in the horn push.
Mike Howlett

If the horns come with a relay then you should use it, to protect your horn switch. My 75 V8 came to me with a moped horn, and as soon I fitted proper horns I found out why! Part of the resistance was somewhere in the column, and part in the Moto-Lita wheel. It was easier to add a relay and get rid of both.
PaulH Solihull

The relay will take the bulk of the current off of your horn switch. The MGB, unlike most cars, didn't use a horn relay. Their thinking, I can only assume, was that the current needed to operate the horn(s) wasn't high enough to worry about. Every other car, that I have ever worked on, has a relay in the horn circuit. When the horn button is held down, for more than a few seconds, the contacts can weld themselves together and make for an embarrassing situation. RAY
rjm RAY

This thread was discussed on 17/02/2011

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