Cabin temp sensor fan won't shut off
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Mudding
Joined: Nov 2014
Posts: 230
Likes: 53
Cabin temp sensor fan won't shut off
The temperature sensor fan under the dash next to the steering wheel doesn't shut off. Even if I take the keys out of the ignition. It keeps running. If the car sits for a day or two, it kills the battery.
Is this a problem with the fan, or is there some relay that is not disengaging. I also noticed that the HVAC system will occasionally stay on as well unless you manually hit the power button. I'm assuming these two are related?
Any ideas? I'm getting tired of having to jump the battery every time the thing sites for more than a day.
Is this a problem with the fan, or is there some relay that is not disengaging. I also noticed that the HVAC system will occasionally stay on as well unless you manually hit the power button. I'm assuming these two are related?
Any ideas? I'm getting tired of having to jump the battery every time the thing sites for more than a day.
Thread Starter
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Mudding
Joined: Nov 2014
Posts: 230
Likes: 53
Anyone else ever experience this?
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Mudding
Joined: Nov 2014
Posts: 230
Likes: 53
That's why I come here for help.
Recovery Vehicle
Joined: Jul 2012
Posts: 973
Likes: 154
From: Mideast US
Disconnecting the motor alone may work to bypass an electrical problem that keeps it on. Disconnecting the assembly plug will impair the heating.
Learned that when I removed the fan/sensor assembly hunting for a rattling noise source.
Learned that when I removed the fan/sensor assembly hunting for a rattling noise source.
Baja
Joined: Aug 2013
Posts: 5,845
Likes: 368
From: Near Bordeaux, France
The cabin fan and sensor are essential to maintain the cabin area at the correct temperatures in climate control and heating. It may be totally blocked up with dust and crud so take it out and clean it first, if it still plays up and continues to run then replace it. It is a tiny fan that draws cabin air over a sensor so prone to clogging up.
Pro Wrench
Joined: Nov 2015
Posts: 1,935
Likes: 189
From: Coastal Georgia
In-car temperature sensor
The in-car temperature sensor is an encapsulated thermistor that provides the ATC ECU with an input of cabin air
temperature. The sensor is integrated into the inlet of an electric fan, which is installed behind a grille in the fascia
outboard of the steering column. The fan runs continuously, while the ignition is on, to draw air through the grille and
across the sensor.
The in-car temperature sensor is an encapsulated thermistor that provides the ATC ECU with an input of cabin air
temperature. The sensor is integrated into the inlet of an electric fan, which is installed behind a grille in the fascia
outboard of the steering column. The fan runs continuously, while the ignition is on, to draw air through the grille and
across the sensor.
Ignition switch supply
When the ignition switch is in position II, the feed from fusible link 8 flows through the ignition
switch to the passenger compartment fusebox on a W wire and passes through fuse 31.
From fuse 31 the feed passes on a GK wire to splice joint A9/A144. From the splice joint the
feed is divided into three separate feeds as follows:
�� A GK wire supplies power to the Air Temperature Control (ATC) ECU.
�� A GR wire supplies power to the in-car temperature sensor.
When the ignition switch is in position II, the feed from fusible link 8 flows through the ignition
switch to the passenger compartment fusebox on a W wire and passes through fuse 31.
From fuse 31 the feed passes on a GK wire to splice joint A9/A144. From the splice joint the
feed is divided into three separate feeds as follows:
�� A GK wire supplies power to the Air Temperature Control (ATC) ECU.
�� A GR wire supplies power to the in-car temperature sensor.
In-car temperature sensor
The in-car temperature sensor receives a feed from fuse 31 in the passenger compartment
fusebox. The feed passes on a GK wire to splice joint A9/A144. From the splice joint the feed
passes on a GR wire to the in-car temperature sensor and is connected to a motor which
draws air over the sensor. The motor is connected on a B wire from the in-car temperature
sensor, via header C0760, to earth header C0017 LHD/C0018 RHD.
A reference voltage from the ATC ECU pin C0791-8 is connected on a BW wire, via splice
joint A145/A146 to the in-car temperature sensor. An input from the sensor is connected on
a WB wire to the ATC ECU pin C0792-7.
The in-car temperature sensor receives a feed from fuse 31 in the passenger compartment
fusebox. The feed passes on a GK wire to splice joint A9/A144. From the splice joint the feed
passes on a GR wire to the in-car temperature sensor and is connected to a motor which
draws air over the sensor. The motor is connected on a B wire from the in-car temperature
sensor, via header C0760, to earth header C0017 LHD/C0018 RHD.
A reference voltage from the ATC ECU pin C0791-8 is connected on a BW wire, via splice
joint A145/A146 to the in-car temperature sensor. An input from the sensor is connected on
a WB wire to the ATC ECU pin C0792-7.
Bottom line unless ign switch in II it should not be powered.
There is not a relay between fuse 31 and the sensor.
......
Last edited by number9; Jan 23, 2018 at 01:38 PM.
Camel Trophy
Joined: Dec 2009
Posts: 3,883
Likes: 951
From: Charlotte
One of the two things other than the sensor powered by fuse 31 is the Air Temp Control ECU. Does the display on the heating-A/C control unit turn off when the ignition is turned off. In other words, does another thing that's supplied with power from the same source also stay powered when the ignition is off?
This is a weird one, especially for a system that is not complex. Are you dead-certain the sensor fan is running with the ignition off?
Let's look at something else. A common cause of phantom battery drain on a DII is the Self Leveling System if the truck once had air springs in the rear that were replaced with coils without the air springs/coils setting being changed in the SLABS computer. Was your truck converted from air springs to coils?
This is a weird one, especially for a system that is not complex. Are you dead-certain the sensor fan is running with the ignition off?
Let's look at something else. A common cause of phantom battery drain on a DII is the Self Leveling System if the truck once had air springs in the rear that were replaced with coils without the air springs/coils setting being changed in the SLABS computer. Was your truck converted from air springs to coils?
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Mudding
Joined: Nov 2014
Posts: 230
Likes: 53
I can literally, open the door, reach into the Rover, hit the power button on the HVAC, and turn on the blower motor.
Without ever inserting the key.
The entire interior heating and cooling system remains on when I take out the key. If I don't remember to manually turn it off, it kills the battery.
Does that sound like the ignition system?
