A/C makes a loud clunck

[mikeg135]

Has anyone had any problems with a loud clunk while turning on their A/C. Mine does it intermittantly. And only after it sits overnight and when the days are hot.



It does this when the A/C first cycles, and sounds like someone just beat the hood with a baseball bat. It also is bad enough to shake that 7000lb monster while it does it.



The stealer could not make it do it, however they were to DUMB to follow instructions on when it occurred.



Someone told me that, it may be slightly overcharged with too much freon(or whatever refrigerant it takes).



Any suggestions would be helpful.



Mike

 

[1tuffram]

My '95 will do it when driving down the highway and I turn it on for the first time. Not sure why it happens but the clunk sounds like something is going to break, so I now turn on the A/C when the engine is at idle. If driving down the highway I will push the clutch in and let the RPM's come down to idle then turn on the A/C. I don't think it has to do with being over-charged because my system is needing a "tune-up", it doesn't cool near as well as when new. I think maybe it has to do with the A/C clutch getting old (just a guess), cause mine never did it when new, just noticed it the last few years. Typically around this time of year more threads will start popping up on A/C and A/C clutch replacment. Some guys have found a few places where you can buy just the clutch and not have to replace the whole compressor ($$$).

 

[lschultz]

I've got 50000+ on mine and it has did this several times since I had it. It has been discussed on here before. Do a search and maybe you will find it. I am not worried about as long as it keeps cooling. I'll see if I can something on it.

 

[RonaldLarson]

Ah, the dreaded clunk

The only failure on my truck has been the AC compressor. It, too, went "clunk" when I turned it on after sitting in hot weather all day. One big difference; it almost stalled the engine! Twice!

Got a new one under warranty because the condition was easy to duplicate in front of the dealer's technician. One scary sound guys, like a gunshot.

Ron

 

[Motorhead]

clunk

The sound could be one of the "air doors" inside the heater/ac unit inside thge truck. Different positions on the dash selector ports vacuum to different air director doors inside to divert the air where you want it. I hear it in my truck but it is not real loud. Try changing the knob while it is on and see if it makes the same sound repeditly

 

[mikeg135]

ol ron,



that sounds about right. the clunk is loud and shakes the entire truck. I am passed the 36,000 mile mark, but it had been in with this reported problem.



Will this be covered under the 100,000 engine warranty? Or will I be fighting the Stealer on this one.



Mike

 

[1tuffram]

Originally posted by mikeg135

ol ron,



that sounds about right. the clunk is loud and shakes the entire truck. I am passed the 36,000 mile mark, but it had been in with this reported problem.



Will this be covered under the 100,000 engine warranty? Or will I be fighting the Stealer on this one.



Mike

I'm pretty sure the A/C is only covered under the 3/36 warranty . Dealers have a way of either: 1) not being able verify / duplicate a problem 2) "It's normal", when the truck is under warranty. Take it back after warranty when you are paying thier shop rates and I'm sure they will have NO problem finding what's wrong. I think DC sends all 5 star Service Dept and Warranty Managers to a class on "The art of avoiding warranty repairs" and the second part of the coarse is "The joy of voiding warranties". Sorry for the sarcasim, I'm in one of those moods today.

 

[Mingoglia]

My '01 ETC has made the loud clunk a few times here in AZ. The first time it did it, it scared the crap out of me. It's probably done in 2 times in the last month.

 

[HoleshotHolset]

Just wait until your starter hangs up and your truck won't shut off... . or when your headlight switch decides to go up in smoke... . or when your transmission doesn't like OD while going down the highway... ...



Those are tense moments..... but would you rather drive a vehicle with no soul?



I have yet to hear the clunk... . but I'm sure I will.....



Matt

 

[MCummings]

My truck has one it several times, but it happens only when the A/C is turned on for the first time when it hasn't been turned on for about a week.



Once it NEARLY stalled the truck,, (Went to about ~450RPM) and the several other times it has happened it rocks the truck pretty hard.



For you manaul transmission guys for a comparison it shakes the truck MUCH MUCH harder than just letting the clutch out real fast in Neutral. The truck actually rocks back and forth a few times recovering. I personally am suprised the Serpentine belt hasn't broken, or Screeched/Slipped when the act does happen.



I'm with Matt on this one.



Driving a Dodge Cummins is driving a truck with personality, they are all different and if you have to explain why you like driving a Dodge Cummins to somebody, then they probably "Wouldn't understand"



Merrick Cummings Jr

 

[HoleshotHolset]

Merrick:



It's Cummins/Dodge... . not Dodge/Cummins.....



I bought an engine... . the truck just came with it. I must admit, the truck itself isn't all that bad... . it's pretty darn good. With the help of the TDR and it's knowledgeable members... . we can make these trucks very reliable, powerful, comfortable, and look good too... .



Matt

 

[Whitmore]

I am by no means a HVAC guru but here is my theory of the clunking , when you s/d the ac unit and let it set a while the freon , or what ever that stuff is they use now,will condense in the compressor, then when you re -start the ac unit the compressor has liquids in it and we all know that you cannot compress liquids just like you cant pump vapors.

I went thru the clunk thing 2 times before I figgered out what to do , so now before I s/d the ac unit I will take the controls out of ac 2 minutes before s/d the truck, havent heard the clunk since ... ... ... ... ... ... ... ... ..... Kevin

 

[mikeg135]

What do you mean by "s/d"?



Mike

 

[Doc Tinker]

I think he means "shut down"



Doc

 

[lschultz]

Whitmore- that kinda makes sense. When I turn off the highway going to my house its about . 3 mile. I started turning the AC off then and just leaving the fan on to run. Started doing this mainly to dry out the evaportor so it would not get that mold smell. Haven't had that smell with this truck like I did my 98 but I was just in the habit of doing it on the 98 so I continue to do it. But for awhile I was forgetting to do it and thats when I noticed the clunk. But I haven't heard it for awhile. You might be on to something.

 

[Whitmore]

yes

s/d is shut down, sorry for the terminoligy we use it daily at the job and its common lingo for me.





Ishultz... ... ... ... ... good one, I didnt think of the added bennifit of the no mold smell, I guess I was getting that too as a bennie ... ... ... ... . Kevin

 

[RonaldLarson]

My failure...

had nothing to do with operating the ac, then sitting at rest, then restarting later. My failure occured after the ac had not been run for at least 24 hours. I started the truck, turned on the air, and "BANG", nearly stalled the engine. The ambient air temp was around 85 degrees. After removal fronm the truck, the compressor was found to be locked up big time.

Ron