Heater temperature dial calibration

[CPN]

Ok, here's one to stretch the brain!

One of the things that I have noticed about the climate control in the Mk4 Yaris is that the temperature set and what you actually get, differ wildly.

If you set the temp to 21°C on the controls and let it settle on a journey, the indicated temperature inside the cabin and also via the OBD port is usually 23-24°C and not 21!

So, I went hunting with the Carista app and sure enough, under customisations, there is a section on Heater controls and particularly "Temperature dial calibration" like this...

This leads to a bit of head scratching because it doesn't really indicate what you are actually changing?

Does anyone actually know? Is it saying that if you set it to -2°C, then 21°C will really be 19°C (but still saying 21)? Or is it saying that the temperature inside the cabin will change by 2°C downwards?

Help!!!

[MikeSh]

1 hour ago, CPN said:

Is it saying that if you set it to -2°C, then 21°C will really be 19°C (but still saying 21)? Or is it saying that the temperature inside the cabin will change by 2°C downwards?

Probably both. It'll reduce the signal sent to the control by 2, but hopefully the setpoint reading will still be 21, and thus the cabin will get 2 cooler. 

If not that then you'll have to try it and see.

[bathtub tom]

I've a similarly, obscurely worded instruction for my home central heating thermostat/programmer. I found it meant the room temperature would have to change by the amount set (one or two degrees), before it would trigger the boiler on or off.

Of course, it may mean something completely different in your case.

[YarisHybrid2016]

It's an offset. Whatever the temperature is set to on the display (e.g. 21) then if you set -2 in the app, the system will set whatever 21 was, minus 2 degrees, as the temperature.

I wondered how accurate it actually was, too.

From what I read, the correct way is to get the cabin to the set temperature, switch off the fan, and measure at chest height at the driver position.

[anchorman]

I’m nesh thanks to beta blockers.  The temp in my Lexus is way off compared to the Yaris.  I could settle for 22 in the Yaris but I’m 25-27 in the Lexus.  I suppose it’s down to calibration and where you measure it but my feet say crank it up.   I’ll rent them to you if you need to calibrate yours.  They like tea.

[APS]

12 hours ago, CPN said:

Does anyone actually know? Is it saying that if you set it to -2°C, then 21°C will really be 19°C (but still saying 21)?

Yes, exactly that. Well, that would be the logical deduction at least.

Have you measured this over a longer trip? All the Toyota and Lexus cars that we have had, that had climate control would, crank up the heat - clearly a bit over the set temperature - for the first 30-40 minutes of a journey and then drop the temperature to at or just below the set temperature after that. 

[MikeSh]

On the MK3 the cabin temperature is measured at the climate control panel where there is a small vent. (The is a little grille on each side, in the corners. The left one has the microphone and right has a pipe going to the return air section with the sensor just visible inside.)

I imagine the MK4 is similar.