Double Bass High-pitched electrical hum

[David Kaczorowski]

Anyone have an idea of what could cause a really high-pitched hum from electrical circuitry? I've heard it before from an old video monitor, but in this case it's coming from behind the dashboard on passenger side of a new truck.

 

[Huy Nguyen]

Bad wiring in your building. Fluorescent lights. Many different things. Those two are most common tho.

 

[Jake deVilliers]

"Those two are most common tho."

Not in pickup trucks HD!

 

[moles]

Is there a speaker or two situated in that area of the truck?

 

[Jake deVilliers]

How loud is it? Can you hear it over the engine or just when you energise the ignition?

It could be part of the injection/computer system doing its thing. My '86 Vanagon with Bosch Digifant injection has an 'idle stabiliser module' that hums quietly to itself all the time. Its very evident when the ignition is switched on, before cranking.

 

[Huy Nguyen]

Oh man, I totally missed the last part. I need to stop reading so fast.

 

[David Kaczorowski]

I discovered it's coming from a silver box with lots of wires (the ecu?) under the dash, behind the glove box. It's audible when the key is turned to on prior to ignition and while the engine is running. Sometimes it's very loud and drives me crazy, sometimes not as loud, but I have very sensitive ears. I am kinda getting used to it. My wife can't hear it without sticking her head under the dash. On another forum I learned it's fairly common and it was suggested that wrapping it in foam rubber silences it. I have to find some foam rubber.

 

[Jake deVilliers]

There's a good reason for putting the engine in the back!

David, you'll need to be careful about wrapping it up and keeping the heat in there. That ECU needs to keep from overheating.