Outside/ambient/climatroinc temp sensor problems

[chrisw4266]

Having an issue with the outside temp reading it's way below what it should be, approx 10 degrees too low. I've tried 3 different outside sensors ( the one behind the nsf bumber grille ) admittedly they where all from scrap yard, but I've checked the resistance on all 3 and they where very similar.I even warmed up the sensors and the resistance changed 

The weird thing is the reading goes up after 5 mins of driving but is still too low, and comes down again in traffic. I've checked at the multi-plug and found 5v on 1 wire and earth on the other, having checked the wiring diagram the 5v comes from the climatronic unit so I'm assuming  that side of things is O.K. any ideas would be great. 

The main reason I want it sorted is this restricts the A/C operation, because first thing in the morning it's reading -11 degrees so won't switch on the A/C which is a pain as it helps demisting. I've even tried disconnecting the sensor and it still gives a reading way below the actual temp.  :think:

[chrisw4266]

Forgot to add it's both the climatronic display and the dash display I assume they use the same sensor.

[mac11irl]

might it just be out of calibration and a plug in and adjust jobby with VCDS?

[chrisw4266]

might it just be out of calibration and a plug in and adjust jobby with VCDS?

Can they just go like that? As it was fine till about 2 weeks ago. Also I haven't got vcds.

[chrisw4266]

Had a go with the climatronic obd and found the reding for the fresh air vent temp fluctuates when driving

This is defo a incorrect reading the bumper sensor reads.

The displayed temp is.

So think my fault is the one sensor behind the pollen filter on top of the air box.

Will try disconnecting it and see what happens.

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[mac11irl]

I had another thought on my way to work this morning, might it be corrosion in the plug?

given that electric thermistors work by resistance increase/decrease with temp change calibrated to

equate the resistance to what it should be at a given a temp.

dodgy wiring somewhere could be adding resistance or dropping the voltage in the circuit which is screwing with the read out..

Edited 13 March, 2014 by mac11irl

[chrisw4266]

I did think that myself gonna remove the sensor on the air box side check plug and wiring and if ok order new sensor. They're only £27 from TPS.

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[IulianE]

strange problem....these sensors are pretty acurate

[chrisw4266]

strange problem....these sensors are pretty acurate

 

 

Turns out its the sensor in the air-box removed it today and reading is much more accurate, so new part arriving Monday and all will be fixed. It's No.15 on this pic.

 

 

They list it as evaporator temp sensor but on elsawin and the climatronic OBD its called fresh air temp sensor. Here's a link to the Climatronic self diagnosis PDF I used may help others with issues.http://www.saunalahti.fi/~jues/Climatronic_Self_Diagnostics.pdf

[IulianE]

what the hell,is another sensor there?

[chrisw4266]

what the hell,is another sensor there?

This ones the fresh air sensor. There's another in the foot well vent and one in the climatronic unit it's self.

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[mac11irl]

makes sense i sopse, climate control needs to know air temp in, air temp out, and cabin temp to regulate properly.

[chrisw4266]

The more I read about the climatronic set up, the more I think 3 knobs is a better bet  

Edited 14 March, 2014 by chrisw4266

[IulianE]

No,I love this climatronic setup...Last summer I was to Greece,I drove from the mountins in Bulgaria where outside temp was 21deg to Xanthi where temp was 46 deg,and I couldn't believe is that hot outside watching the dash reading,but when I opened the window it really was.In the car I didn;t noticed the smallest rise in temp.

[eka567k]

How did you get to that temp sensorunder the pollen filter please? Look like a right pita!

[shm]

This thread sounds like exactly the same issue I'm having with my octavia - the temp displayed is always significantly lower than it really is.

I'll try disconnecting the air box sensor and see if the readings are more accurate.

What's the part number for this, should it need replacing?