Hey guys, newby here to the forum. I'm on my second 3rd gen RAM. My first was an 03, and I recently bought an 08 Hemi QC.

My problem is that when idling, I feel a harmonic vibration through the steering wheel. The vibration cycles about every 2-3 seconds. This only happens when the AC is running. Thinking it could be the AC compressor, I turn off the compressor. However, the vibration continues until I hear the AC condenser electric fan shut off. At this point the vibration completely goes away and does not return until I turn the AC back on. Thinking the electric fan is out of balance, I check the fan but do not feel it vibrating...perhaps there is some resonance between the fan and the engine? I also notice the idle RPM is about 600 with the AC on, and it drops to about 500 with the AC off...so maybe the vibration is related to idle RPM? My 03 never had any of these vibrations.

Thanks in advance for any and all ideas. I dont have confidence the dealship will be much help...so I want to be armed with some ideas when I bring it in.

RamTX08

 

Test test. The forums won't let me post a thread.

 

2-3 seconds is much longer than then the period of anything rotating on that engine. what you are experiencing is the superposition of two different waves that happen to align every 2-3 seconds. sorry i don't know exactly how the accessories are set up on the rams (yet), but assuming they are all belt driven by one serpentine, if you feel it in the steering, my guess is that the compressor is the problem, and you're feeling it through the belt, through the power steering.

 

Yes, the AC compressor is my initial thinking...but when turning it off (with the compressor button) the vibration continues until later when I hear the condensorcooling fan turn off. The vibration is completely gone at that point. Also...one other thing is that with the AC on, the vibration goes away if I rev the engine a bit > 700 RPM. I did read that a previous year model had a TSB (TSB 11-002-05) for some exhaust vibration that sounded very similar to what I am experiencing. I assume the 08 models would have corrected that issue.

 

After more troubleshooting...I think the AC Condenser electric fan is causing the harmonic vibration felt in the steering wheel. It may be the combination of the fan runningalong with the engine/accessories. But when this fan shuts off the vibration goes away. I can reproduce this behavior by turning the AC on, then off, then waiting for the fan to turn off. At least thats something I can show the service department...

RamTX08