Just bought a used 2007 RX400H and found that horn does not work properly. It creates a sound, but gives ~10 times less sound than required.
I have cheched the fuse. It's OK. Also, the alarm produces good sound, so the horns are fine. Could it be a relay or switcher problem? if so wehere they located? I have another RH400h where I removed all visible switchers (2 boxes with fuses), but they seems to have no effect on sound.

Any idea? Thanks

 

Interesting experience: I connected the horns directly to battery. The sound was low, so something was with the horns or there are 2 relays from alarm and horn itself. Then I changes one horn from another Lexus (I have 2) and it was working fine. So, I removed horns and paid attention that water is leaking from one of them. It appears that horns have minor holes in the body and somehow water was collected inside. I stressed the horns and removed at least some water and connected them back to the battery. They are working somewhat better, but still need some drying. I think the water could penetrate in the horns during high pressure washing.

 

Is this on your RX? If not what ride?

 

The horns on the RX are in front and are facing down. They are the trumpet style, one high and one low. Both of which have relays.