Thermometer Issue

Angus1990 · Jan 8, 2014

Hello

Recently when I get in my Range Rover in the morning the thermometer reads 24 Degrees when its more like 4 outside! After driving for a bit it does go down to around 10 but its defiantly colder outside...!

Where is the thermometer sensor and has anyone else experienced this?

Many thank for your help!

Angus

wammers · Jan 8, 2014

Behind grille to right hand side. Though early models had it fitted into inlet ducting of L/H blower fan.

Moreirinha · Jan 8, 2014

If you read the ETM it´s explained there that only after reaching a certain speed for a certain amount of time the becm will assume that the temperature reading is the correct one, so first thing in the morning will be a default value..

Datatek · Jan 8, 2014

Moreirinha said:
If you read the ETM it´s explained there that only after reaching a certain speed for a certain amount of time the becm will assume that the temperature reading is the correct one, so first thing in the morning will be a default value..

Really? Mine gives pretty accurate readings from start up, certainly not a default reading. It's on the nearside or on you right if you face the front of the car.

wammers · Jan 8, 2014

Moreirinha said:
If you read the ETM it´s explained there that only after reaching a certain speed for a certain amount of time the becm will assume that the temperature reading is the correct one, so first thing in the morning will be a default value..

BECM has no input into Hevac ambient temp reading. It is a function of the Hevac unit alone. Think that is more to do with changing a sensor, were the Hevac will not change the reading from that of the old sensor to that of the new one, until the vehicle is moving at 15 MPH or more for a period of time.

Moreirinha · Jan 8, 2014

It´s the HEVAC not the BECM, my mistake.

but:

"Ambient Sensor
This sensor measures the temperature of the
external air flow into the vehicle.
The ambient temperature sensor is located behind the
LH side of the vehicle in front of the condenser. The
revised location improves the response time of the
sensor. The new HEVAC software will not update the
ambient temperature sensor readings unless the
vehicle is travelling over approximately 15 mph (25
km/h)."

Datatek · Jan 8, 2014

Moreirinha said:
It´s the HEVAC not the BECM, my mistake.

but:

"Ambient Sensor
This sensor measures the temperature of the
external air flow into the vehicle.
The ambient temperature sensor is located behind the
LH side of the vehicle in front of the condenser. The
revised location improves the response time of the
sensor. The new HEVAC software will not update the
ambient temperature sensor readings unless the
vehicle is travelling over approximately 15 mph (25
km/h)."

Well, that's would seemt to be wrong, I can park mine with +11C on the display and come out in the morning and it's shows, correctly, -5C for example with the snowflake ice warning illuminated.

wammers · Jan 8, 2014

Datatek said:
Well, that's would seemt to be wrong, I can park mine with +11C on the display and come out in the morning and it's shows, correctly, -5C for example with the snowflake ice warning illuminated.

Of course he missed the text off that said after a new sensor had been fitted. If the sensor is reading wrong and you change it, the new sensor will not register a change on the Hevac readout until the car has travelled forwards at 15 MPH or more for a period of time.

Datatek · Jan 8, 2014

wammers said:
Of course he missed the text off that said after a new sensor had been fitted. If the sensor is reading wrong and you change it, the new sensor will not register a change on the Hevac readout until the car has travelled forwards at 15 MPH or more for a period of time.

Fairnuff

Moreirinha · Jan 9, 2014

"Ambient temperature damping
When the ambient temperature increases, the ATC
ECU imposes a rate of change limit of 0.5 °C (1 °F)
/minute. When the ambient temperature is decreasing,
the ATC ECU accepts an unlimited rate of change.
Ambient temperature input strategy (from VIN
381431)
The ATC ECU incorporates a software strategy to
overcome the effect of radiant heat from the engine
and cooling systems on the ambient temperature
sensor:
At vehicle speeds of 15 mph (24 km/h) and
above, the input is considered valid and
changes are accepted. The value of the
input is stored in memory and constantly
updated while the vehicle speed is above
15 mph (24 km/h).
At vehicle speeds below 15 mph (24 km/h),
changes of input are considered suspect
and changes are ignored. In place of the
actual input, the ATC ECU uses the value
stored in memory.
When the ignition is switched on, if the
ATC ECU detects warm heater coolant, it
uses the ambient temperature stored in
memory. If the ATC ECU detects cold
coolant, it uses the input from the ambient
temperature sensor."

I knew had seen some where...
But apart to trying to prove you guys wrong, not my intention as we all know the invaluable knowledge so many time shared by both of you, my point is when i start the car in "extreme" temperatures, cold or hot, it takes a while to get the correct reading.

wammers · Jan 9, 2014

Moreirinha said:
"Ambient temperature damping
When the ambient temperature increases, the ATC
ECU imposes a rate of change limit of 0.5 °C (1 °F)
/minute. When the ambient temperature is decreasing,
the ATC ECU accepts an unlimited rate of change.
Ambient temperature input strategy (from VIN
381431)
The ATC ECU incorporates a software strategy to
overcome the effect of radiant heat from the engine
and cooling systems on the ambient temperature
sensor:
At vehicle speeds of 15 mph (24 km/h) and
above, the input is considered valid and
changes are accepted. The value of the
input is stored in memory and constantly
updated while the vehicle speed is above
15 mph (24 km/h).
At vehicle speeds below 15 mph (24 km/h),
changes of input are considered suspect
and changes are ignored. In place of the
actual input, the ATC ECU uses the value
stored in memory.
When the ignition is switched on, if the
ATC ECU detects warm heater coolant, it
uses the ambient temperature stored in
memory. If the ATC ECU detects cold
coolant, it uses the input from the ambient
temperature sensor."

I knew had seen some where...
But apart to trying to prove you guys wrong, not my intention as we all know the invaluable knowledge so many time shared by both of you, my point is when i start the car in "extreme" temperatures, cold or hot, it takes a while to get the correct reading.

Don't think that is any different than either Keith or i said to be fair. There was one version of the Hevac that had problems in displaying temperature but it was sorted on later versions. On the version that had the problem if the day was bright and warm and your temp read -15 obviously the sensor was duff. But if you changed the sensor the temp would still read -15 regardless of engine temp until the the car had been driven at +15 MPH for a short distance. That was changed on later versions to be as stated in the last sentence. At least that is my understanding.

rasheed · Jan 9, 2014

My temperature sensor has never, ever read true. From new. Usually raises the value by 5 - 7 degs. Like setting your watch ahead by 10 minutes I just ignore it. Everything seems to work fine anyway. Oh and mine's in the blower duct.

wammers · Jan 9, 2014

rasheed said:
My temperature sensor has never, ever read true. From new. Usually raises the value by 5 - 7 degs. Like setting your watch ahead by 10 minutes I just ignore it. Everything seems to work fine anyway. Oh and mine's in the blower duct.

That is the early version that had the problems i think. When it was moved the Hevac got a software upgrade.

Thermometer Issue

Angus1990

New Member

wammers

No longer with us, RIP

Moreirinha

Member

Datatek

Well-Known Member

wammers

No longer with us, RIP

Moreirinha

Member

Datatek

Well-Known Member

wammers

No longer with us, RIP

Datatek

Well-Known Member

Moreirinha

Member

wammers

No longer with us, RIP

rasheed

Well-Known Member

wammers

No longer with us, RIP

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