Whistling sound from the dash area

[Carl Boudreaux]

Hi to all I am new to the forum and have a problem with a whistling noise i need help with
I have a 2004 Beaver Monterey 40Ft with the Cat engine and while driving I hear a rather load whistling sound that come from under the dash area and mimics the sound of the engine. The sound gets louder while accelerating and when shifting occurs the sound diminishes. Could this be coming from the air pressure gauge or is there any vacuum line that may operate anything in the the dash area? The sound seems directly related to the engine rpm that why I think it is a vacuum line but I do not know if a vacuum line is used to change a/c or heater vents or does anything else with the instruments or other devices and may be leaking causing the whistling sound?  If anyone  has  any ideas or experienced that kind of sound while driving a similar unit I would appreciate your thoughts on what I might look for to eliminate the annoying sound...Thanks in advance for your help... Carl

[Roy C Tyler]

 Is the volume turned up on your rear camera?  Could be hearing the engine turbo through the speaker.

[Edward Buker]

Carl,

The vacuum line for the dash AC/Heat is run off an electric pump given diesels do not pull a vacuum. There is no engine tap for a vacuum source like in a gas engine manifold. You might try an inexpensive mechanics stethoscope and try and source the noise. Any auto parts place will sell one. As Roy points out most cameras have a microphone that may be run to the radio or display electronics.

Later Ed

[Carl Boudreaux]

Thanks for the replies did not know there was a volume on the rear camera but will definitely check that... Carl

[Joel Ashley]

Nice catch, Chuck!  I'd forgotten the many times I've left the rear camera's audio turned down but just audible enough for me to scratch my head where the odd noise was coming from, perfectly in synch with the engine revs  .  It's a very likely answer to Carl's question.

If you have a Sony Alladin monitor, Carl, there is a volume knob on it.

Joel