Periodic chirp and stumble with fan on?!?

[Robs]

I have noticed a periodic "chirp" while driving when I have the fan controls set on auto. The chirp seems to be coming from behind the dash or the engine compartment. For a while I assumed this was related to fan bearings going bad (which it could be). However, when it chirps you can detect a slight engine stumble. It took me a while to figure out that it only happens with the fan on auto (on). It has occurred to me that the stumble might cause the chirp - meaning that the two things are unrelated.

I have read that this might be related to the A/C compressor. I have noticed that occasionally on start-up there is series of chirps/squeal that sounds belt related. I have had the truck die on me out of the blue while driving twice. Had the dealer go over it and they could find nothing wrong. Overall the truck is in excellent condition but with almost 200,000 miles. I thought I would appeal to the great collective brain (forum) for insights.

Thanks, Rob

 

[ezdaar]

Remove belt and wiggle all pulleys. look for ANY wobble.
Check tensioner, does it move back and forth any?

Your "chirp" is a very fast and minor belt slippage, its cause by the compressor temp locking or a pulley being dumb due to the extra load the comp puts on it.

buy a New belt before checking pulleys. No reason to take off old belt and not put a new one on while checking pulleys.