TCS Horn relay question

[rjbaren]

I bought the compact air horns from R.D. Enterprises.  I removed my old "Clear Hooters"  horn and installed the air horn.  Not too bad a job.  The box shows a relay and I was all set to do it with the relay and fished a wire to the fuse box but then I decided to see what the horn sounds like and it worked fine without a relay.  So I installed it without a relay thinking, there is no power going through the horn till you beep it and even then it is not usually on for a very long time.   Is it OK to skip the horn relay?

[Grumblebuns]

Any high amperage component on a car should have a relay to actuate it. Remember that all of the current is going through the horn switch when you operate the horn. When you release the button, the break in current will cause a arc across the horn contacts. Over time the build up in scale on the horn contacts from the constant arcing will cause a reduction in voltage to the horn and possible failure to operate when you most need it. I would install the relay myself.

[BDA]

 

The best thing is to take as much load off as many switches as possible.

[jbcollier]

Generally speaking, most air horn compressors draw more current than the stock horn so it is a good idea to fit a relay even though it works without one.  Some compact air horns meant for motorcycles would be fine without a relay, and more than loud enough.

Most common air horns (Hella, “Maserati”, etc) take a wee bit of time to spool up.  I use a much larger compressor from a Citroen DS.  The horns come instantly on and are much louder.

[GavinT]

Installed a set of Stebel Nautilus compact air horns similar to the RD ones on my daily driver.
The Stebel ones apparently draw 18 amps, so definitely need the relay I reckon.

[rjbaren]

All right, glad I asked. 

If I were to add relays to my headlights I assume the wiring would be similar?  A separate power and ground.  I also assume the power would come from the hot side of the fuse box with an inline fuse of about 20 amps?

[jbcollier]

Take it off the brown side so you go through the least number of switches and connections.  Better yet is a feed straight from the battery but that is a long way in a Europa.

Use Lucas 35 amp fuses or US 15 to 17 amp fuses.

[rjbaren]

I installed the horn relay today and the horn still works.  I tried like the dickens to fish something through the console to the engine compartment with no success.  So I connected my fused wire to the brown wire side of the fuse.  I had to move my radio hot wire from the brown wire side of the fuse to the white wire side of the fuse and now the radio can only be on when the ignition switch is on.  The horn is always live.  It could be my imagination but the horns seems louder.

[BDA]

Good job! You could have had some losses in the switch so your horn might actually sound louder. In any case, you have a better a arrangement now.