4th Gen - Horn Not Working

[Scott560]

I've tested both horns with direct power to them and have deafened me.

I don't know anything about 4th gens, but if you can hear relays clicking when pressing the horn button, then it suggests either relay output is not present, or the wire is broken (assuming the horn earths to the slam panel, confirmed by the fly lead test hopefully), or some incompatibility between the engine loom and body loom.

Plenty of hours on your back upside down under the steering wheel for you!

I guess the next tests would be:

1) confirm the pinout of the relay so you know what is what.
2) confirm that the input to the relay works via the horn switch (we assume this already works)
3) Confirm that you have 12v ready on the input to the output side of the relay (eg 12v is ready to go when relay output closed)
4) with the relay removed confirm that using a bridging wire will sound the horn (probably won't).
5) check continuity between the relay output pin and the horn input, This is where you (and i) suspect there is no continuity (hence no power).

I'm guessing that point 5 is the key, the output of the relay must not go anywhere, probably because of a mismatch between the body and engine looms? Maybe you will need to re-pin one of the multiplugs.

Good luck!

[arif_manji]

have you tried this first suggest of scotts? i would do this then work backwards - the replacements you've used may be faulty

Have you tried running a 12v fly wire to the horn to check the horn sounder physically sounds?

I have indeed. Also, any parts that were replaced were tested on the donor Prelude. Then the original part fitted back. Both horns are working, tested with a 12v fly wire too.

[arif_manji]

I've tested both horns with direct power to them and have deafened me.

I don't know anything about 4th gens, but if you can hear relays clicking when pressing the horn button, then it suggests either relay output is not present, or the wire is broken (assuming the horn earths to the slam panel, confirmed by the fly lead test hopefully), or some incompatibility between the engine loom and body loom.

Plenty of hours on your back upside down under the steering wheel for you!

I guess the next tests would be:

1) confirm the pinout of the relay so you know what is what.
2) confirm that the input to the relay works via the horn switch (we assume this already works)
3) Confirm that you have 12v ready on the input to the output side of the relay (eg 12v is ready to go when relay output closed)
4) with the relay removed confirm that using a bridging wire will sound the horn (probably won't).
5) check continuity between the relay output pin and the horn input, This is where you (and i) suspect there is no continuity (hence no power).

I'm guessing that point 5 is the key, the output of the relay must not go anywhere, probably because of a mismatch between the body and engine looms? Maybe you will need to re-pin one of the multiplugs.

Good luck!

Hi @Scott560,

I think there is a incompatibility between the engine and body loom. I'm going to try and obtain the loom from someone who is breaking a Prelude in Suffolk as I have scrapped H22a donor Prelude I had. The 4th Gens don't have a earth point on the slam panel like the 5th Gen do.

Thank you for those steps, ill try them in a few weeks.

Thanks again.