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Cabin Fan

8K views 8 replies 8 participants last post by  TonyInMemphis 
#1 ·
Have something odd, while parked, and I think driving, the cabin fan changes speed, and I didn't touch it.

First I thought it was like my Volt as it changes fan speed when your on the phone. And which is what I was doing waiting to close out my service ticket.

But it just seems to randomly change speed, and usually not different speeds, just whatever it's set at and then lower, then return back to what it was, after a while.

Haven't seen anyone else come across this yet.
 
#2 ·
I don't spend much time parked with the fan on, but I have noticed that my fan noise seems to change when I am on the highway. I haven't experimented with it much yet, but it seems like when I go past a certain speed, it is automatically going into 'cabin recirculate' mode and then back out again when I slow down. It feels like the airflow rate changes, and the noise changes, but it seems like it is the same change that happens when you hit the recirculate button.

Maybe this is a feature and not a bug? It is a bit strange when it suddenly seems to have a mind of its own - it's not like we have automatic climate control...
 
#3 · (Edited)
Me too. Same thing as you. I assume it must be when the front rad fans kick in
and draws that much power,or the computer is doing a charge for the battery?
It seems to last about 5 minutes if I recall.

(Edit) Now that I thought about it. It does not do it when the rad fan kicks in.
 
#4 · (Edited)
I think this is that darned auto-recirculate thing. While driving, try pushing the recirc button. If it lights but you hear nothing happening (ie., actuator closing/opening door), then its already recirculating. I've noticed if I push the button again (for fresh air) the light goes off, then I hear the door/actuator move, the fan is a bit quieter, and I smell fresh air. But it only lasts one minute, then it goes back into auto-recirculate. The description in the owner's manual lists a whole set of conditions necessary for auto-recirculate to happen: high outside temps PLUS fan on high PLUS temperature selector all the way to "cold" PLUS vent settings anywhere from front A/C vents to floor vents - but this simply isn't true. It auto-recircs when the dash says the outside temp is 82 - warm, but not really hot enough to warrant auto-recirc. It does it when the fan speed is set halfway. I've tried setting the temp selector one notch back from full cold - still it auto-recircs. And it seems even the heat/defrost combo settings allow auto-recirc. The only way I've found to guarantee I'm getting fresh air (while smoking) is to set the system on full defrost. It doesn't cool as well of course, but at least I'm not running my smoke thru the system. Sure wish there was some other way to modify the auto-recirc deal! Hate it! *I* should be able to decide if I want to recirculate or not.

But then, yes, I need to quit smoking.:|
 
#5 ·
I have also noticed a fan speed change while idling and wondered why. While I was in the shop with my PM the tech was telling me about how great it was that we have a fresh air AC filter. If I'm understanding it correctly it filters the air when you don't have recirc selected. Could it be that having recirc off only works when air is forced into the system by way of the van moving forward?
 
#6 ·
Well see, I'm wondering if the fan speed change you guys are hearing is really just that it sounds louder because its gone into recirculate mode. That's what mine does. And perhaps its not always noticeable when traveling at speed. (When it auto-recirculates the little green recirc light on the fan knob does NOT come on.) I'm wondering if the system is designed to go into recirc so much, so easily or if something is wrong with mine. I can force it into fresh mode by cycling the recirc button on then off. But it only stays in fresh for one minute then returns to recirculate. I can clearly hear (and smell) this happening. Is this what others are experiencing? Granted, I'm in Texas and its hot here.
 
#7 ·
I've noticed the change in fan sound a couple times now. I've had it on one of the higher fan settings, A/C on, and while accelerating to get on the highway it sounds like the fan speed increases. Didn't know anything about "auto recirculate" going on.
 
#9 ·
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SAME ON 2020 RAM PRO randomly it changes not cooling when it slows down. High if cools great did any find out what this problem is.
 
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