Interior temperature sensors - Where are they? What are they

[BenH]

A simple question of curiosity: where are the interior temperature sensors in my W210 E200? And what are they?

The air conditioning reacts impossibly quickly to changes in the interior temperature (when I open a window, for example) and I just can't work out what would react so quickly to the temperature. Where are the sensors? I can't see anything that looks like a sensor, but they've got to be in the middle of the car somewhere to keep the back seat passengers happy, surely?

(Mine's the simple AC, with the thermostatic temperature control, but not full climate control.)

TIA,
Ben Harvey

 

[Matt Crooke]

Interior temperature sensors

I cant actually visualise the dash layout of your car, but generally, on or near the A/C controls there will be something that looks like a tiny vent. This would be the sensor. I know its a totally different car, but in my old Rover Sterling, there was a little black dome, about the size of a 20p piece on the top of the dash, near the screen demist vents, this was the sunlight sensor for the climate control. The actual temp sensor was to the left of the heater controls, and again was a slotted vent type thing. The same applies to my father inlaws 2001 Peugeot 406, the little vent is actually on the A/C control panel. I notice on my 190 (which dosent have aircon, but some do have i believe) on the interior light surround, next to the seat belt warning light that flashes for a bit when you close the door, there is a slotted vent looking affair, i would imagine this is where the temp sensor would be had aircon been fitted.  

Hence, tonight i will expect you to be on your driveway looking for mysterious vents all over the interior of your car!!!!

All the best.

 

[BenH]

Interior temperature sensors

Ah-ha! You may well be right. Because I'm a sad nerdy type and I love my car, I've  spotted such a slatted vent near the rear-view mirror in the past. That must be it.

Thanks! I shall go and pipe steam on to it and then blow cold air and see what happens!

(Edited by BenH at 12:49 pm on Aug. 28, 2002)


(Edited by BenH at 12:51 pm on Aug. 28, 2002)

 

[BenH]

Interior temperature sensors

Actually, no. Thinking about it I'm not sure you're right - the E-Class has independent temperature controls for the left and right of the car, so there must be two sensors, I would have thought. I haven't actually gone out to the car and looked yet, but I will. I'll let you know what I find!

Ben ("Sherlock Holmes") Harvey

 

[Matt Crooke]

Interior temperature sensors

Good point actually Sherlock, ive got dual temp in my 190 as well. Because of that perhaps im wrong about the mystery vent. Please let me know what you discover, as im intrigued now!!!

Good luck in your quest!

 

[Martin]

Interior temperature sensors

From previous experience with a C class, and my current E class looks very similar, I believe you'll find the sensors under the slotted vents to the left and right of the rear view mirror surround.

 

[BenH]

Interior temperature sensors

You're right - I've just been out to look. However, I think I'm being cheated by MB!There's only one temperature hole, so presumably only one sensor.

I'm now baffled by this: if the left and right controls are set to different levels, what temperatures does the system pump through the vents? Perhaps the dials only adjust the vented temperature in relation to the average internal temperature. So, if the sensor detects 18 degrees near the mirror and the passenger control is set to medium-hot then the passenger gets 18 degs vented air plus an arbitrary level of heat added. If the driver's control is set to normal (white) then the driver gets 18 degs air, until the whole car heats up from the passenger's side, after which the driver's air will (presumably) get cooler.

Hmmm.... I'm not convinced. Could this work? Am I taking this far too seriously?

We need someone who knows these things to explain the theory. Andy? Are you there? Someone put me out of my misery, please!

(Edited by BenH at 2:10 pm on Aug. 28, 2002)

 

[Matt Crooke]

Interior temperature sensors

I think Einsteins theory of relativity would be easier to explain than this one!!!

 

[rpalmeida]

Interior temperature sensors

Theres 1 temp sensor (with a blower fan in it to recirculate the air thru it), probably on the over head control panel.
If the fan is working, it will hold a 1cm by 1cm piece of paper in place because of the fan sucking air in.

The dual temp controls dont need two temp sensors, it can use temperature of the water returned from the heater stuff - and theres more than one of those sensors.

If you hold down the rest button for about 10 seconds, you get diagnostic mode on the display of the aircon (if you have climate control that is)
- it shows the test number on one side of the display and the value on the other. Certain buttons will cycle up and down thru the tests  (can remember which).

From memory test 1 is the inside temp, test 2 the outside temperature

Cheers
R

 

[BenH]

Interior temperature sensors

A mini-fan in the overhead trim panel? Temperature sensors in the heater matrix water return pipe? Water return temperature being an indication of the interior temperature of the car?

Sounds bizarre, but I'll take your word for it!

 

[rpalmeida]

Interior temperature sensors

Try the paper trick - the mini fan is certainly there on newer vehicles.

Ill dig out my list of the test numbers for the climate control - its an interesting insight into how this all works !
The aircon actually uses the outside temp to adjust the actual interior temp to make up for the way people perceive temperature when getting into a car from a cold or hot outside temperature !

R

 

[Matt Crooke]

Interior temperature sensors

Ahh, ive just been reminded of something. There was a post on here about 6 months ago of a guy who's car started making a very irritating whirring sound from around the sun roof area. He searched everything, and kept being puzzled as to why the sound slowed down and stopped when he switched the ignition off. Then someone on here pointed out that there is a little fan in the light surround etc etc.

So it is true, there is a fan up there

 

[BenH]

Interior temperature sensors

Wow. Those clever chaps at Mercedes think of everything!

I was thinking about the paper test - static electricity would have a similar effect, although Matt's mention of someone with a problem in that area justifies the fan theory.

My system isn't the full climate control - just the thermostatic temp control. You're right about the exterior temp sensor having an effect on the AC. My outside sensor went bananas earlier this year and registered temperatures of over 40 degrees. Until I fixed it, the temperature inside the car became unbearably cold!

I'll try sticking something into the roof fan to see what happens, like naughty schoolboys do with fans!