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Old 05-17-2019, 11:22 AM   #1
vanhoozj
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Question Help identifying a sound behind center console

Iíve got an 86 240 that is making a noise from behind the center console by the center vents. Iím not sure itís the blower motor but wanted to see if anyone here has had a similar experience before I go that route.

To me itís sounds more electrical vs mechanical; like the dull spinning noise of a motor being turned by hand almost a grinding or growling kind of thing. The sound begins when I am up to roughly 20-25 mph and air is coming through the vents even with the blower in the off position. I know airflow in the off position is partially by design with the A/C system.

The noise increases in speed as I accelerate and airflow through the vents also slightly increases. The noise goes away when the car is at a slow enough speed and airflow decreases as I decelerate. Once stopped there is no air flowing through the vents and no noise, again all of this is while the blower is in the off position.

The blower fan works in all positions and has no effect on the sound. Iíve pressed in the recirc button to attempt to eliminate airflow into the air box from the cowl and it doesnít affect the sound either. The noise remains both while recirc is engaged or disengaged.

My initial thought was that somehow air is passing through the firewall and spinning one or both of the impeller fans causing the motor to rotate; therefore, making the noise. I canít see anywhere that air is getting into the firewall as all the grommets look intact and sound.

Iíve also checked for exhaust leaks as a trusted mechanic suggested. The car has a larger exhaust than stock and a larger cat, but no luck isolating the noise to a leak.

Another mechanic simply said it's the blower motor but the motor operates fine at all speeds, no noise when Iím idling or under 20mph and this noise occurs even with the blower in the off position again at higher speeds so Iím just not sure thatís the issue.

Any suggestions?
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Old 05-18-2019, 12:25 AM   #2
stove
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Is the A/C knob FULLY turned Counter Clockwise? You damn near need to use pliers to get it to it's full OFF position.
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Old 05-20-2019, 09:40 AM   #3
vanhoozj
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Is the A/C knob FULLY turned Counter Clockwise? You damn near need to use pliers to get it to it's full OFF position.
Yep, as far as I can get it turned to the left in the Off position.
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Old 05-20-2019, 09:59 AM   #4
apachechef
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3 position fan speed switch with a 4 position resiter?
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Old 05-20-2019, 09:39 PM   #5
vanhoozj
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3 position fan speed switch with a 4 position resiter?
4 speed fan switch
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Old 05-20-2019, 11:16 PM   #6
bobxyz
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From the passenger footwell, take off the center console side cover, stick your head all the way forward and, with a flashlight, look above the tunnel at the front of the air box. You should see the big recirc flap. At idle, push/pop the recirc button and see if the flap moves. From your description, I'm wondering if you have a vacuum leak and the recirc flap is staying in the no-vacuum recirc/opened position.

Even so, I'm not sure how this would be related to the noises. As a different experiment, you could tape over the cowl vent, or stick a sheet of cardboard under the hood, across the cowl, and tape it to the windshield, then go for a drive and see if the noises are different.
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