TRWright

works fine with engine off. ideas?

2001 tt

TRWright

horn works perfectly with key off. turn key on and no horn.

SSST

No idea why that would be the case. Has the car had any electrical work done on it recently?

jpflip

First time that I read a problem with the horn...May be your ignition switch? Weak ignition switch was related in many cases with headlights problems, a/c problems.... But this is only a guess. Can it be the relay? Easy to troubleshoot because you can switch it with the one in position 12, fog light, it is the same part number. The horn relay is in position 10. And the relay part# is 141 951 253 B. The relay carrier #1 is located at your foot , a bit left of the driver side ....