What is the low humming or fan noise in the CAB

Tiny
STEFFAN279
  • MEMBER
  • 2004 MITSUBISHI CARISMA
  • 156,000 MILES
I have a low humming noise or what sounds like a fan in the dashboard just after starting the engine all electrics are off ie fan radio etc
Tuesday, November 8th, 2011 AT 10:38 PM

1 Reply

Tiny
DRCRANKNWRENCH
  • MECHANIC
  • 3,380 POSTS
If the heater fan is off, there are only a few things that I can think of;

The valve that changes the flow into the heater caore, which adjusts the interior heat, might not be closing all the way and creatting a high pitched noise.
The thermostat might be stuck partially open and stuck in a position it does nto normally operate in which could cause a high pitched noies.
Resonance from interior metals or engine bay parts could vibrate against each other and casue noises.
There could be worn out accessory belts that needs replacement or adjustment.
The power steering level may be low.
The timing chain/belt could need replacement.

Check out those possibilites and maybe try to see where the noise sounds like it is coming from if the hood is open and you look around for its source.
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Tuesday, November 8th, 2011 AT 11:13 PM

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