[Mgs] 1980 MGB wiring question

[Michael MacLean]

Speaking of horns, my 1969 MGB GT has only one horn.  Is that original?  It
has two wires going to it.  It works OK, but it just sounds weak.  What is
a good alternative?  Can I wire two horns here?
Mike MacLean

On Tue, Aug 10, 2021 at 2:49 AM PaulHunt73 <paulhunt73 at virginmedia.com>
wrote:

> The horn wiring changed on late model cars so that the stalk button puts
> out 12v to the horns, and the horns only have one wire each as they pick up
> an earth from their mountings.
>
> As such the horn push should have purple (12v, fused always live) and
> purple/black (to the horn) wires.  First thing to check is, does the
> interior light work? If not maybe the purple supply from the fusebox has
> failed, bottom fuse.
>
> If so, with it lit press the horn button.  Does it go out?  If so then
> there is a bad connection back through the fusebox.
>
> Next it depends on whether it is easier for you to check the wiring at the
> multi-plug by the column, or at the horns.  In the former case look for the
> purple and purple black wires and check them (connector still plugged
> together) for 12v on the purple all the time, and on the purple/black when
> the button is pushed.  If on the purple but not the purple/black the switch
> or wiring in the stalk is faulty.  Sometimes the wires are moulded into the
> connector blocks so you can only test by parting the connectors just enough
> to expose the pins, but they are still making contact.
>
> At the horns with the button pressed you should have 12v on the
> purple/black spades on the horns (wiring connected).  If not and the test
> at the column multi-plug was good then the circuit back to there is faulty,
> most likely is a bad connection between the wiring connector and horn spade.
>
> If you see 12v on the horn spade check a clean part of the horn body for
> 12v as well. If you see that then the horn earthing is bad.  If you saw 12v
> on the purple/black spade but not on the body then the horn is bad
> internally.
>
> It might seem unlikely that the fault is at the horns in both cases, but
> anything is possible.
>
> BTW stuff the trumpets with rags to avoid getting a loud blast if you
> disturb the fault and one or other should suddenly start working :o)
>
> PaulH
>
> ----- Original Message -----
>
> We’re working on a 1980 B with a maddening assortment of electrical
> problems.  Right now we’re trying to figure out why the horn push won’t
> work—and all the wiring diagrams (Bentley & Advance Autowire)—show the horn
> as having purple wiring—apparently meant for the  horn push in the steering
> wheel button, not the push-in-the-wiper-stalk of this car.  Any advice from
> the List?
>
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