and i know where it is coming from..... sometimes when i turn on the AC there is a loud thunk coming from the hump in the floor. what's under there???

 

That could be the door in the blower housing closing the outside air vent when you switch to max AC. Make sense?

Hobbit

 

I'm with Hobbit.

 

I just experienced this thunk the other day. It's the compressor trying to pump oil. Instead of compressing a gas, it's compressing a slug of oil and this causes the thunk. The compressor is at the bottom of the system and if you don't run it for a couple of days or so, the oil drains down to it.

It should only thunk once and only after the a/c has been OFF for a while. If you run the a/c every day, I don't think you'll hear the thunk.

 

My F150 also makes this 'thunking' sound. Is this a 'normal' sound or a potential problem? Has anybody asked Ford or their local dealer about this sound?

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2000 F150 XLT 4.6V8 4X2 SS SC Deep Wedgewood Blue

 

when it comes to the ford a/c package be thankfull its only a thunking noise. as long as it consistantly is blowing cold air and is reliable your doing fine. there are a number of vent closing and opening proceedures that occur when the a/c begins operation, as well as some mechanical operations that occur.. the compressor is located on the passenger side bottom front of the engine. have it checked if it continues, when it comes to a/c units preventive maint. is much cheaper then repair.

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2001 Super Crew 4x4, Amazon Green Lariat, Med. Parchment Leather, 5.4 liter, Keyless Entry, Towing Package, Captains Chairs, 6 CD Changer, Running Boards, Duraliner, Limited Slip, 3.55 axle, Skids, and Slider, K&N Equipted