Noisy Air Conditioning Compressor

[ScottGreen]

I've got a '06 3500 Dually. In addition to the loud bump when the A/C is turned on, I've also got a roar after the A/C runs for a few minutes. Is this a normal thing, or do I have a bad compressor? It seems to blow cold, but it sound awful, especially going under an overpass. Sound stops if I turn off A/C.

 

[roperteacher]

My 06 had a humming vibration issue, only when the compressor was on. I think the roar you are hearing is the fan clutch?

 

[rbattelle]

Sounds like the fan, which must activate at low speeds to provide sufficient airflow to the condenser.

Ryan

 

[Tejasdge]

I have concerns about my AC clutch, mine has a loud metallic slap sound that I never heard until this past year when the truck is first started up with the AC on. Earlier this summer, at just under 90k on the stock system, I added a bit over 12 oz of 134a because it was freezing up and showed low on the gauges. Cooling was greatly improved, but the slap persists. Is there any adjustment in the clutch, or do I just wait for a very hot day in the middle of nowhere?

 

[Crunch]

I have concerns about my AC clutch, mine has a loud metallic slap sound that I never heard until this past year when the truck is first started up with the AC on. Earlier this summer, at just under 90k on the stock system, I added a bit over 12 oz of 134a because it was freezing up and showed low on the gauges. Cooling was greatly improved, but the slap persists. Is there any adjustment in the clutch, or do I just wait for a very hot day in the middle of nowhere?

Mine was freezing up too. Turned out to be a problem with the evaporator not regulating and/or monitoring the system. Fixed on the skin of the teeth of the warranty. No problems since the repair, but it's only been a couple of weeks.

 

[JDerrick]

Mine will engage with a load slap also now and then ... ... ... ... .....

 

[Tejasdge]

I remember the discussion a while back about the freeze-up TSB. I believe moving the evaporator sensor was part of that fix. I had no problems with freezing until the system got low on 134a. I just hope it hangs together for a while longer and will hold this charge.

 

[rbattelle]

Mine freezes up a lot. I regulate it myself by turning off the compressor for a few minutes. I'd rather do that than deal with dismantling the dash.

Ryan

 

[Crunch]

I remember the discussion a while back about the freeze-up TSB. I believe moving the evaporator sensor was part of that fix. I had no problems with freezing until the system got low on 134a. I just hope it hangs together for a while longer and will hold this charge.

That's interesting because I remember a similar discussion. But when I asked the service guy about TSBs for the AC he said it was for the 1500s. After I described the symptoms he said I needed a new evaporator. I haven't had any real disappointments with my truck, but the AC is the critical feature I am least impressed with. You'd think that as important as the AC is the manufacturers would just go ahead and put an oversized AC in vehicles, especially heavy duty trucks. The AC in our trucks should be able to freeze raw fish, and the vents should move the hair on people in the back seat when it's set to high.

 

[Tejasdge]

Now that we have hijacked the thread, I have no major complaints about the AC when your scooting down the highway. But when you try to cool it down in 100+ degree weather from an idle or in stop and go traffic, it dissapoints. I would like to add a pusher fan for such instances.



I have never seen anyone mention this, but when my truck is in park idling, if you bump the throttle it will idle up to over 1000 rpms. Mines an 03 so I can't get the cruise idle up flashed since the early 3rd gens are (what is politically correct) missing quite a few bytes that should have been in thier DNA, umm, memory string.

 

[rbattelle]

but when my truck is in park idling, if you bump the throttle it will idle up to over 1000 rpms.

Wow, I've never heard of anyone doing this. Pretty useful I think. I'm quite certain mine won't do it...



Ryan

 

[jman]

My 03 does the same thing and it is not normal. I think the FCA is bad and causes the idle to stick. Mine didn't start this until about 85K and it is a 95K now. I need to get it in and get it fixed before 100K. Mine is way worse when it is cold. Every stop sign you roll up to the idle is stuck at 1000 rpm until you let out the clutch in gear then is idles down. Nothing major, but it can be a pain at times.

 

[Tejasdge]

Dang it JMAN, you made me go out and get some learning on FCA's. I have avoided the CP3 mod threads since I don't/can't need/afford to have another item on my wish list. I have the Outlook and have not noticed a drop in rail pressure, but will pay more attention. When I'm in gear, I don't have a high idle problem, it only seems to do it in park. I'll play with it in different gears and see what happens.



For those that want more information, I found this thread;



https://www.turbodieselregister.com...7/162586-modded-cp3-issue-maybe-not-hmmm.html



Interesting and lively discussion.

 

[JDerrick]

I had a manual throttle advance in my 99'. when parked for long periods on rescue scenes and such I left the auto trans in neutral set the park brake and spun the motor up to between 1500 and 2000 rpms, and it blew ice cubes from the dash in the middle of summer in the Las Vegas desert ( 115 deg plus at times) . the AC NEVER missed a beat, and the truck never over heated in this configuration. I have had similar luck with the 06' with the electronic throttle . place in neutral set brake and run at 1500 rpm. stays cold. HOWEVER I have noticed that in traffic the AC does have some trouble keeping up until you are moving nicely down the road.

 

[jman]

I'm sorry I stirred up a hornets nest for you!:-laf I first noticed mine rolling up to a stop sign in neutral and the silly thing was stuck at 1000rpm. I put in 1st and started to engage the clutch and it idled down. It is very pesky in cold weather, but acts up quite often all the time. If I rev the engine it takes 2-4 seconds to idle back to 750 rpm. It's like you are holding the throttle and just slowly easing off off it until it's back to idle.



I should just go buy the part and change it. It isn't hardly worth taking it to the dealer even if it is under warranty.

 

[hsmith]

Have you guys checked the low pressure switch? It should cycle the compressor to prevent freezing unless you leave it on low fan speed for a long time.