Heater Temperature Control

Hi,
Have searched the forums but can't find anything the same as my heater problem. If I have the heater on 22 both sides the temperature keeps on going up so eventually you have to open the windows! If you lower the temperature the fan speed seems to slow down, but the air coming out of the vents is still really hot even when the car inside temp is well over 22 and the heater is set to 16. If I put the heater on LOW then it does go cold, but put the heater back up to 16 and you get baking hot. I have checked that the cabin heat sensor fan is running and fluff free. Anyone any idea what I should check next?

The Temp settings is to set the internal temp to the desired level no the heater output level...

So if the car is at say 5degC and you set it to 16...the heater will supply hot air until the interior is close to 16...it will then reduce the outlet temperature and modulate the temp and distribution to maintain that selected Climate level...

If after a while the temp is still hot...I would be looking at the blend motors...

Do you have the Book symbol up on the display??

There is no book display and as I said, if the heater is set to just 16 the temp in the car goes way beyond comfortable i.e. well over 22 and I then either have to open the windows or set the temp to LOW and then it goes cold very quickly.

We have found that you can't have either side more than 6 digits out from each other but do have a book symbol come up on display sometimes.
O/s tends to be really warm in ours where n/s I would say is about right - if a bit on the cool side sometimes.
Sorry can't help - we new to our p38 and still learning lots !!!

Maybe it is time to get it on a full fat Diagnostics device to recalibrate the Blend Flaps and use it to force them each position and observe the temp output....could be they just require a recal so they know there set positions per temp setting!

Could be the little fan in the dash that supplies cabin temp to the sensor - next to the radio (small grill) or blends.

as above....I have checked that the cabin heat sensor fan is running and fluff free. Anyone any idea what I should check next?

Saint.V8 said:

Maybe it is time to get it on a full fat Diagnostics device to recalibrate the Blend Flaps and use it to force them each position and observe the temp output....could be they just require a recal so they know there set positions per temp setting!

Click to expand...

Could be the actual sensor then as the blends usually cause the chequebook symbol

jeffers said:

as above....I have checked that the cabin heat sensor fan is running and fluff free. Anyone any idea what I should check next?

Click to expand...

That does not mean the sensor itself is not faulty. As you have no book symbol, it's unlikely to be the blend motors. You need to look at the cabin sensor output on diagnostics. Also check the external air temperature sensor, does it give the correct temperature on the HEVAC display?

Datatek said:

That does not mean the sensor itself is not faulty. As you have no book symbol, it's unlikely to be the blend motors. You need to look at the cabin sensor output on diagnostics. Also check the external air temperature sensor, does it give the correct temperature on the HEVAC display?

Click to expand...

Apologies for the delay in responding, other non Land Rover issues interupted me.
I assume the sensor is a thermistor, if so I will check it tomorrow. The external temperature seems to display correctly. Does anyone know if I can get the diagnostics output without going to a main dealer ie anyone with the required device to read the codes anywhere near me in South Wales?

Made some progress, ill share what I did for others.
I decided to remove the HEVAC control unit and do the checks on the leads going from connectors C245 and C246b.

Here are the details of the pins for the sensors and the readings you should get with a multimeter.

Outside air temp C245 pins 7(White/Black) & 8(Blue/Orange) reading at 12 degrees is around 17K ohms

Internal air temp (aspirator) C246B pins 9(Brown/Blue) and 18(Black/White) again at 12 degrees is around 17K ohms.
If you blow in the hole in the dash the reading in my case went to 14K ohms within a second or so.


Heater core temp C246B pins 2(Slate/Orange) and 10(Black/White) this is a different type of sensor and will read open circuit with a meter.
I took it off and put a meter with a diode checking position across the sensor and heated it up with a soldering iron. The reading did change so I assume it is OK. I'm going to change this anyway as I broke the bracket when I took it out (new one = £15)
This sensor being removed does bring up the book symbol on the HEVAC but the heating still seems to work.

Changed the sensor and the book symbol no longer showing. All seems to be working OK.