relay race

[Baz]

I seem to have onset relay failure !!
Now horn has stopped working and two speed fan switch has stopped. (1977 Spider)
Does anyone know if these functions are connected to a relay somewhere, of which there seems to be an endless supply in the dash area.
I replaced the control switch on the steering column (wiper, main beam, turn signals) and the relay for the wiper circuit.....nuthin.
Anyway , I either have bad relays or bad earth somewhere.....
Thanks
Baz

[18Fiatsandcounting]

I'd check the fuses first. Fuse #2 (B) is for the heater fan, and Fuse #9 (I) is for the horn. Fuse #1 is closest to the steering column and Fuse #10 is towards the outside.

Since Fuse 2 and Fuse 9 are unrelated circuits, I'm thinking it's coincidental that both your horn and heater fan stopped working at the same time.

If the fuses are OK, check that each fuse has +12V on it. Fuse 9 (horns) has power all the time, while Fuse 2 (heater fan) is only powered when the ignition is on.

-Bryan

[Baz]

thank you Bryan,
All fuses seem to be ok...the horn, after I improved the earth, then pushed the button seemed to get a noise response from a group of relays, but the horn sound itself weak...
I have three relays in the same area where that came from, so i'm thinking there is a problem there, to be honest, the car has been converted to RHD and the loom as best I can tell is ordinary. So I just gotta keep trying, probably and auto electric guy...
but thanks for the response..
baz

[18Fiatsandcounting]

...the horn, after I improved the earth, then pushed the button seemed to get a noise response from a group of relays, but the horn sound itself weak...

Do you have the original air horn with a compressor, or a modern electric horn (no compressor)? If the air horn, the compressor may need a cleaning and rebuild. After this many decades, sometimes they just get jammed from old oil and don't spin very well.

-Bryan

[Baz]

no...just the horn unit, no compressor. I have so many little boxy relays in the loom, I am thinking relays.....as when I re-earthed the horn, I got a croaking sound each time I pressed the horn, from a cluster of 4 relays on the engine well bulkhead, with the odd toot here and there. When I held down the button for 3 seconds...all went silent.
Anyway...Oh the joy.....
cheers
Baz

[18Fiatsandcounting]

It sounds like you have a modern horn, and those are grounded simply by being bolted to the car body. If you have +12V to the power lead of the horn when you press the horn button on the steering wheel, and all you hear is a "croak" or a "squeak", then that sounds like you simply have a bad horn.

If you aren't getting +12V to the horn, then yes, I would suspect a bad relay or poor connections. Usually the way it works in Fiats is that the horn button on the steering wheel grounds the relay (which has +12V all the time), turning the relay "on", and that supplies +12V to the horn.

-Bryan