Weird Noise: Cause for alarm or Normal? Help Please

[DeluXXXe]

I have a 2007 Jeep liberty with about 18K miles on it, bought used from Chrysler in September.

I noticed in October that the engine will make a weird noise (how can I describe a noise here?) when the engine temperature gauge is midway, never heard it when engine is cold.

Its not from the fan, it from this "thing" circled in red. Im not a gear head, I have no idea what it is (so what is it?) The belt runs over it and while the engine is running the outer part of this "thing" spins, but every like 30 seconds the INNER part of this will click on and spin for about 10 or 15 seconds and then stops. It continues over and over. I opened the hood and saw this happen and pinpointed the source of the noise. It makes a noise which I can hear and feel in the car (like waiting at red light) its a minor noise though, almost like the engine is revving a little harder. The headlights will dim EVER so slightly when it starts and return to full brightness when the noise stops and the inner part of this "thing" stops spinning.

So, is this a cause for alarm? What is this device?

My warranty runs out at the end of 2010, so I figured I had time to worry about it later if a problem comes up... BUT with Chrysler's future in question I want to take care of it now if its a problem just in case Chrysler isnt around in 2010.

Ps. this photo was found on the web, its not MY engine. It is a Liberty 2007 engine though.

Help?

And Thank you all in advance...

 

[tommudd]

Thats your AC compressor, it does kick on every so often to circulate the cabin air, if it extremely loud the bearings maybe going out so you need to get it checked as soon as possible, if it freezes up then the belt will come off and no power steering, alternator will not charge etc.

 

[DeluXXXe]

Hmmmm So if the fan isnt on in the cabin.... Shouldnt make any noise?

I got to give that a shot.

Thanks.

Its not that it makes an abnormal noise, just never encountered that before. Is dimming of lights and noise normal?

 

[JeepJeepster]

Its normal for any car that has A/C.

Remember your liberty will turn the A/C on in every position except for the 'face' position.

If the belt starts squealing then the bearings are probably shot. Replaced the A/C compressor on a 94 ZJ last summer but it had 160k miles at the time.

 

[Corwyyn]

Remember your liberty will turn the A/C on in every position except for the 'face' position.

I thought the only time the A/C would run without the button pushed was in the 'defrost' position (the A/C coming on to help dry the air and clear the windows faster).

 

[jnaut]

Its normal for any car that has A/C.

Remember your liberty will turn the A/C on in every position except for the 'face' position.

'Face' position? What year do you have?

My 04 turns compressor for Recycle, the two snow-flake (air conditioner) positions, and the two defrost, main and floor. But the two positions without 'snowflakes' on them, floor, and floor/face have no compressor.

 

[JeepJeepster]

I thought the only time the A/C would run without the button pushed was in the 'defrost' position (the A/C coming on to help dry the air and clear the windows faster).

That all changed in 2005+ libertys.

On the 2002-2004 it will only run on Defrost/feet and pure defrost. And of course it will run if you have it in a A/C position.

'Face' position? What year do you have?

My 04 turns compressor for Recycle, the two snow-flake (air conditioner) positions, and the two defrost, main and floor. But the two positions without 'snowflakes' on them, floor, and floor/face have no compressor.

See sig. Mine is the same as yours.