Horn not working

[TomScrewz]

I have a 2001 1.3 Corolla.

My horn works when the ignition is off. When I start the car the horn doesn't work. So I can't use my horn while driving. I replaced the horn relay but the problem remains.

Does anyone know what the problem is?

[oldcodger]

Hi,

Have a listen, or check with a multimeter, if you can hear the relay clicking when the ignition is on and your press the horn button.

If nothing then suspect the fault is around the steering wheel.

However you need to take extreme care and follow a Battery / airbag  disconnection routine before doing any work around that area as you could set the airbag off, even causing serious injury.   Probably a job for a garage/auto electrician.

Diagram below is from a later model but expect its very similar to yours.

 

[TomScrewz]

1 hour ago, oldcodger said:

Probably a job for a garage/auto electrician.

I think I'll just take it to one.

[Mooly]

Strange problem.

Has it worked normally in the past or, have you just acquired the car and find it doesn't work. If the later then I would suspect some 3rd party wiring changes might have been done, perhaps in the fitment and removal of any in car entertainment systems.

[TomScrewz]

8 minutes ago, Mooly said:

Strange problem.

Has it worked normally in the past or, have you just acquired the car and find it doesn't work. If the later then I would suspect some 3rd party wiring changes might have been done, perhaps in the fitment and removal of any in car entertainment systems.

I've owned this car for 15 years. This problem just started mysteriously. The horn functioned normally before.

[oldcodger]

Think I would suspect the spiral cable inside the steering wheel /column, or some other wiring down there, but you need to have all  other points checked properly before having that replaced.

You can see what iI mean in this video , skip throgh to about 7mins on .

https://www.youtube.com/watch?v=VblczY9PzMc

[Mooly]

3 hours ago, TomScrewz said:

I've owned this car for 15 years. This problem just started mysteriously. The horn functioned normally before.

That's very strange then.

Further to @oldcodgersuggestion I'm also wondering if its worth you checking all the fuses (there will be more than one fusebox remember)... hazy thinking... could the horn relay be being 'back fed' from somewhere else when the ignition is off and not getting a supply when on. I know that sounds bizarre and crazy but its worth a look.

[oldcodger]

Really needs a volt meter in the relay socket coil pins to see what is going through and then perhaps some resistance / short  checks. 

The Horn Button switches the coils  0v connection, could be + is getting on to that lead when the ignition is on ?

Hard to really say exactly  without being there ....

[TomScrewz]

I came across a similar problem here:

https://mechanics.stackexchange.com/questions/3197/horn-hooter-works-when-car-is-off-not-when-car-is-on

 

Here is his final feedback:

"Just to report back - I hate leaving questions unanswered on the Stack... forums.

 

I don't understand it, but when my mechanic swapped the 2 wires that connect the horn-push-button to the steering wheel, the horn started working properly.

 

Perhaps this had something to do with grounding or something...

 

Anyway, there it is - thanks for the other suggestions all."