Hilux 4x4 Forum

Hi All,

I performed a compression test today and afterward while I was re-assembling the horn started blaring incessantly. I pulled the fuse which stopped it however after putting everything back together and taking it for a test drive the problem persists! (when the fuse is plugged in)

The good news is that the compression was consistent and I was able to clean the surprisingly dirty throttle body and MAF sensor.
1 - 150
2 - 160
3 - 150
4 - 160

But now I have no horn.

I had a look in my Haynes manual but it was of no use.

It is possible that this was a huge coincidence as the horn wasn't working when I purchased it AND when I drove it this morning I felt a few drops of water fall onto my feet (heavy rain in Melbourne ATM)

Appreciate any leads!

Once I get the horn fixed I plan on checking the valve clearances, loving the car so far

Hmmmmm ..... a number of possibilities. It appears that in the course of your work that you may have somehow either pinched a cable, shorting it out or reconnected what may have been previously disconnected.

Firstly I wonder if the contacts in the steering wheel behind the horn button haven't fused or stuck closed. Follow the wires and loom from the horn and look for any damage. Another area of possible damage is inside the fender where the loom from the fuse box under the hood passes through the engine bay side-wall into the fender space. The loom can chafe through there sometimes and create a short. Also where that same section of loom passes into the cab in the area of the fuse box behind the kick-panel.

Go over all the areas where you worked and look for any possible causes.

Well I stuck my head under the footwell and everything looks fine except the steering shaft (uni joint thing) is caked in fluff and crap.

Wires look fine in the engine bay too. Is the horn relay behind the driver footwell fuse box? Should the relay click when the horn is depressed because mine does not. Or would it not click because the horn fuse is pulled?

Looks like a fiddly job to access the rearside of the fuse box.

Thought it was something to do with the hazards as they don't work but then I realised they share the same fuse lol

I'm not sure if the horn circuit has a relay but if it does, that might be the most likely suspect - contacts could be fused inside, in which case it may not click when energised, but it's worth a try. Disconnect the horn itself and listen if there's a clicking when you connect / disconnect the fuse. If there is then you should be able to locate the relay, remove it and test it.

After a bit of dismantling I was able to remove the horn relay which is behind the driver foot well fuse box, ordered a new one that will arrive tomorrow.

Fingers crossed this solves the issue. Short of removing the entire steering wheel and checking the column I'm not sure what to look at next?

To recap - the only electrical things that were pulled are MAF, Ignition Coils and the EFI Fuse and the horn started blaring while they were all out.

Apparently some cars horns will blare as an anti-theft feature however I can ensure you that my basic poverty pack Hilux has no anti-theft features

I noticed that when I put the negative lead back on the car I can hear an electric whirr / pump noise, is this normal?

Probably the HP fuel pump for the EFI. You should only hear this when the ignition is on. Try locate the source of the whir to satisfy yourself that it is indeed the fuel pump.

Good news!

Horn is functional again.. however I cant 100% say if it was the relay at fault. I discovered that the wire connecting to the horn had a little black heat shrink that is obviously protecting some dodgy wiring that was tucked behind the radiator. I have wrapped in as a short term solution. But my thinking is that perhaps water got into it? and shorted the relay?

I would have thought a fuse would have blown before the relay?

Regardless it now works! I am quite paranoid that it will go off again though

Good to hear! I'm sure that's been the fault.