Ok, its finally cooled off enough in Phoenix to have a reoccurring issue that I have not seen/heard since last winter. Goes like this:


The truck has to be moving at about 45mph or anything higher. If the AC is off, but the ReCirc button on there is a "chirp" from the fan unit under the dash. The "chirp" sounds just like parakeet. Now the funny thing is the "chirp" is on a 15-17 second cycle. The fan speed has no effect on the loudness nor the frequency of the chirping sound. Its loud enough that you can hear it over the radio. Turn the AC on and no chirp. Turn the AC off, and the chirp returns. If the truck is not moving, or less than about 45mph, no chirp. One other thing, with the AC off and moving at 45+mph, I can make the darn thing chirp every time by switching from the outside vent to Recirc. It never does it going back to the outside vent from the Recirc, only from vent to recirc. What the devil is going on here?

The chirping I get is from the fan belt chirping every time the A/C compressor cycles. Remember the compressor is on and cycles in the defrost modes regardless of temp setting. My chirping noise you would swear is coming from the steering column under the dash. As far as being related to recirc setting, not a clue. If the fan switch is off, the compressor won't cycle at all. Hope this helps!


Mike

Mine does not seem to be related to the AC compressor at all. AC on = no chirp. Only with AC off, Recirc on, Fan at any speed except off. Higher or lower speeds do not effect the 15-17 second intervals between chirps. The chirps seem to be coming from the fan motor area under next to the floor and below the glove box. Irritating little bird!

Mitchagain - Well, after spending all summer in there, I bet the little critter wants the paper changed in the bottom of the cage! http://www.dieselplace.com/forum/smileys/smiley36.gif





edit - Hmmm - What keeps the flapper door closed on these things. Recirc inside air - over 45 mph - there c/b enough external air pressure build up that the ( probabaly) ?electric motor? and the "closed flapper" position sensor need to activate to reposition (close) the flapper. Under 45mph - not enough air pressure to force the flapper out of position.





hmm - going out of recirc not chirp, into = chirps - could there be a slight binding when the flapper 'closes' / repositions.


So how the heck does this thing work, anyway? Edited by: MTTwister