Small motor keeps running after engine off??

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  #1  
Old 02-25-20, 02:36 PM
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Small motor keeps running after engine off??

So I'm the guy that asked about the little blue light a month or two ago (still a mystery) on my "new" 2012 Scion xB. Now I've become aware of another mystery: After shutting off the engine but leaving the switch on "Accessory" (ACC) (to listen to the radio during lunch, for example) I've noticed a barely audible motor/fan sound coming from immediately behind the dash. Once the switch is turned off, it stops. Turn on ACC again, it starts.
The only reason I noticed it, is that the bearings are shot, and it rattles after reaching a certain speed. It will rattle then run smooth, then go back to rattling, in 1/2 to 2 second intervals. The rattle can be heard with the engine off, but to hear the smooth running, you have to put your ear to the center A/C outlet. It sounds like a very small fan of some sort. (The regular A/C fan is off, of course, and anyway, it's blower is down near the floor). Now it seems that if the ignition switch has been off for some time, turning the switch to ACC will not cause it to run, but if the switch has been off for only a few minutes, the mystery motor will turn back on when ACC is selected. There's nothing in the rather extensive Owners Manual about it (In fact, most of the Owners Manual is CAUTION/WARNINGS....). Any ideas?
 
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Old 02-25-20, 02:45 PM
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Try just turning off the radio and see if the fan stops. Some built in radios have small built in fans to keep them cooler.
 
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Old 02-25-20, 05:16 PM
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Son had Scion, no radio fans.
I'm leaning towards a relay humming.
 
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Old 02-25-20, 05:30 PM
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It rattles with radio off (can't hear it with radio on anyway) and it's not a relay....a small motor shaft makes a distinctive sound when the bearings have gone out.... altho it may not be the motor bearings themselves, but rather the squirrel cage blower or fan bearings the motor is driving. I can't feel any breeze coming from the vent tho, but I can't think of anything else a small motor would operate behind the radio.
 
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Old 02-26-20, 06:28 AM
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Check the floor vent, HVAC direction doors usually default to the floor when the engine isn't running. So it may indeed be the HVAC blower running on slow speed to keep air moving through the cabin.
 
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Old 02-26-20, 07:12 AM
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IIRC, some manufacturers have a "fume fan" that pulls gas fumes into the charcoal canister after engine shutdown.

Check a Chiltons/Haynes manual or parts list for "fan" and see if anything shows up in the dash.
 
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Old 02-26-20, 07:16 AM
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My 89 K1500 did that till I moved to temp control a little off full hot. I think those door motors return to a certain spot when you turn the key off.

If it is a door motor, good luck getting to it under there.
 
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Old 02-27-20, 06:10 AM
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Fume fan runs several hours after engine shutdown and is in the rear. Next to fuel tank.
If it's indeed blower motor running, likely, climate control is off some, still powering it with fan in Off position. So is the fan switch in ON or OFF?

leaving the switch on "Accessory" (ACC) (to listen to the radio during lunch, for example) I've noticed a barely audible motor/fan sound coming from immediately behind the dash. Once the switch is turned off, it stops. Turn on ACC again, it starts.
 
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Old 02-27-20, 08:18 AM
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The fan switch is off, that's the whole point. I suppose it's possible the main blower could be running at a very low speed, but when it's turned on to any of it's 4 speeds, there's no rattling at all. It runs smooth as silk. This sounds like a separate motor, very small, and not a door actuating motor. It's like a fan running at very low speed. @Hal_S, any online wiring diagrams for cars you know of that don't charge a fee?
 
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Old 02-27-20, 09:31 AM
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You might want to try on Scion owners club sites.

 
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