Defroster noise

[Jimmy9190]

This may be one for the tribologists here. I recently had to replace the blower motor resistor in my truck. So now it moves a lot more air with more velocity thru the AC and defroster vents. That was earlier this summer when the temp control was always on maximum cool or not too far from it. Everything was fine this past summer.

Now it is getting cold here and I used the heat/defrost setting this morning for the first time this season. I live in Florida so "cold" means it was about 55 degrees this morning on my way to work. Anyway, with the fan setting on its second lowest speed and the temp selector in about the middle between cool and warm, there is a whistling sound from the top center windshield defroster vent. If I leave the fan on the second setting and move the temp selector a few degrees one way or the other, the noise stops. If I put it on the lowest fan speed the noise stops. Of course if I put the fan on high speed I hear no noise. The heater function in my truck is set up so that a minimal amount of air comes out the defroster even when the full floor heat is selected on the dash control panel. I get a little air out the defrost on AC and dash vent output too.

Anyway I am wondering if any BITOGer's have any idea on the whistling noise. I looked down the defroster vent and saw no obstructions or anything else to cause the whistle. I wonder if "warm" air exiting the defroster vent moves slower and the air on the middle temp setting is moving at just the right speed and temperature to make this noise?

Any help here is greatly appreciated.

 

[EricZoom]

Just a suggestion, but you might try changing the cabin filter if you have one in that truck. Somtimes certain noises in the system can come from there. I also hope it remains "cold" here for the time being. It feels great.

 

[Jimmy9190]

Truck is a 2001 Dodge Dakota. It doesn't have a cabin air filter. I went out and pulled up the header panel and removed a 3 inch piece of foam insulation tape from the edge of the opening on the defroster vent and ran the engine and defroster just sitting in my carport. I was thinking maybe the edge of the foam tape was sticking out into the defroster vent just enough to catch the air flow and whistle like that. The noise sounded like it was still there, just not as loud. I'll have to drive it tomorrow morning and see if it has really changed anything. I have a feeling that this is probably something I will just have to learn to tolerate.

I am realy enjoying our cold spell too. This is what makes it worth putting up with the heat and humidity here in summer. I did some work on my truck on Sunday and didn't even break a sweat.

 

[Jimmy9190]

I found a cure for the noise. It's called a radio volume knob. The noise is still there and I have no idea how to get rid of it. But I can mask it with the radio or change my heat and fan settings. Once I get the truck warmed up I usually keep it on the lowest setting anyway.

This is just something I will need to get used to.

 

[mechtech2]

Your temp control is simply moving a door that routes air .
At that angle, and with that air flow, you are getting a whistle noise.
Simply adjust it away with a minor twist of the wrist.

 

[GMBoy]

Originally Posted By: mechtech2
Your temp control is simply moving a door that routes air .
At that angle, and with that air flow, you are getting a whistle noise.
Simply adjust it away with a minor twist of the wrist.


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