Buzzer always on!

[jpomerenke]

Hello,

Hopefully someone can help me.  Just bought a
1968 250SL

When I start the car, an annoying buzzer start buzzing someone behind dash cluster.  Sometimes it will take a second to start buzzing, but seems to kick in when RPMs go up.  (ie: may not go on the second I start the car, but if I rev the engine it will kick in)
I am assuming this is the buzzer for door ajar?

Buzzer will not go on with key in ignition and door open.  Only when I start the car.

I have taken out every relay and connection I can find under dash and even fuse #1.  Still wont go off.  This has me stumped.   electrical short or some sort?

Any ideas?  Or better yet, where is the buzzer coming from and how can I just disconnect it? 

[mrfatboy]

Could this noise becoming from the tach because of a worn gear?

[Atazman]

I suspect mrfatboy is correct in diagnosing the tach being the problem.  Suggest disconnecting the tach drive cable beside the engine to see if the noise goes away.

[Pawel66]

Same thought came to my mind- the sound of a bad tacho can be similar to an aggressive buzzer noise.

As a quick check - put the tip of your finger on the tacho - can you feel it vibrate a bit? If it does - you know what it is.

If tacho is not vibrating, it can still be the tacho or its cable. The disconnecting of the cable as the next step can help determine that.