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Discussion Starter · #1 ·
I have a 2008 f450 KR and when it is on defrost or a/c i get a clunking noise every 60 seconds or so..... just one clunk at a time does it once then it's gone. i can feel it in the floor boards and it sounds like it is coming from passenger side. thanks in advance.

Kevin
 

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No clunking here. Why in the heck would you have air conditioning? Cooling anyway, I know ya need the heat!!!. Sorry I'm an aircraft mech. Most folks don't realize air conditioning also means heat.

737tdi
 

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I can't say I've ever heard it.

I can say that I use a/c year around in the south if needed. Not so much where it's dry but in the near 100% humidity we have it seems to work much better. Of course you still put the heat on with the compressor running. Doesn't the compressor come on when you use defrost?

Basically when I see a/c I think compressor. Hot or cold. As in the auto part 'a/c compressor'.
 

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You just bought the truck, take it to the dealer... and make them fix it!!!!
 

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Hey Kevin, I have a 05' F250 and mine does the same thing,but not all the time. It drives me up a wall.( only does it when the A/C is on).
 

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Not sure if the systems are anywhere close to the same but my 04 Expedition did that and they replaced the compressor and I think the evaparator and it quit doing it. Same thing though, mine would rattle the floor boards when it did it.
 

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Mine does it as well, i dont worry about it i guess, just thought it was the compressor clutch engaging and disengaging... mine makes a similar clunking while switching from p to d or p to r
 

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Mine also makes that noise. I guess I figured it was normal... Let us know if you bring it in and they are able to fix it.
 

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I have a 08 6.4 that had a noise in the passanger floor, Found that the down pipe was hitting the frame.I repositioned the pipe with a prybar to give proper clearance .The pipe is on a compression flange to the turbo so it came be pushed over with out having to loosen the bolts.Worked for me no trip to the dealer.
 

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I talked to Marc about this a few months back. All it is, is vaccum closing a valve. mine does it everytime. some are louder then others. He said it was normal for this to happen.
 

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Ah yes. That noise. I have not heard it on this truck but I have heard it before on others. If that's what it is though it should only do it when you change the air flow. Does the air change direction when you hear the noise?
 

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Discussion Starter · #15 ·
no it does not change direction. the dealer says it is normal and some trucks are louder than others....
 

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Reviving this topic. My 08 F350 KR has a clunking noise every 20 seconds (yep, timed it)when the defrost is on. Any ideas?
 

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open your hood and watch the AC compressor pulley. they click when they engage, and cycle like that. i dont think youll be able to hear it in side the truck though =\

good luck
 

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It is the compressor clutch you are hearing and there is a TSB on it, take it to your dealer. I think they install a different accumulator on the ac system.
 

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It is the compressor clutch you are hearing and there is a TSB on it, take it to your dealer. I think they install a different accumulator on the ac system.
can this TSB be found online? I would like to have in hand if I took to my dealer...so they dont just blow it off
 

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this is what I have found


A/C clunk :TSB 09-4-1 - AC ACCUMULATOR ASSY - thumping or bang noise from the A/C unit. This noise happened each time the A/C engaged.

I think this is the one.......
 
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