The needle from the temperature gauge drops when the heater is running. When the heater is off, there is no issue. When the car is stationary and the heater is on, the temperature drops even faster. At the same time, the air coming from the vents feels colder. The more I increase the heat output, the faster the temperature drops.

When I turn off the heater, the temperature needle returns to normal. I have already replaced the thermostat, but the problem was not resolved. All possible checks were carried out, but nothing was found. The car stayed at the garage for 10 days, and they still couldn't identify the problem.

They told me it might be an issue with the ECU or the instrument cluster. What’s your opinion? Any advice would be appreciated.

As no one else has replied, my 2p worth (not worth 5p?) Is it the simple controls or the DEATC (dual, fancy) system?

I'd be using Forscan and looking at any and all temperatures engine, inside, outside, both sides to see if there are any clues?

Your post implies that the amount of heating supplied to the inside can drag down the entire system which does seem strange?

4 minutes ago, Shearers said:

As no one else has replied

Are you talking to yourself again ? 🤣

Maybe @efstratn is still waiting for a reply and didn't want to nag?

As usual, I'm aiming to be welcoming and start a dialogue, if he comes back or not.

We shall see, or not

On 4/27/2025 at 6:34 PM, unofix said:

Are you talking to yourself again ? 🤣

Hi. My car has DEATC. I have downloaded the forscan. I have purchased an OBD II and I am waiting to start investigating the malfunction of my car. Does anyone have any idea of what the problem might be?  

33 minutes ago, efstratn said:

Does anyone have any idea of what the problem might be?  

I'm not sure you actually have a problem. The 1.6 Tdci engine does not produce a huge amount of excess engine heat, unlike a 1.6 petrol engine. In an ideal world an internal combustion engine would produce no excess heat.

When you have the cabin heater on then much of the heat from the engine is used by the heat exchanger in the cabin, and therefore it is usual that the engine temp would drop. When the engine is at idle then it will be produce much less heat then when running at 3000rpm, so again no real surprise that you would see the engine temp drop further.

 

For those wondering what DEATC is:-  Dual-Zone Electronic Automatic Temperature Control.

2 hours ago, efstratn said:

I have purchased an OBD II

Hopefully it's a Forscan compatible (i.e. V-Linker etc)?
As above, lets not second guess it and have some temperature data and trends from engine, interior and DEATC at warmed up idle and on the motorway (record the temperatures and no operating computer for safety sake - or get someone else to make notes or you do that with another insured driver?)
If unsure how to use Forscan, look at Skoda Yoda on You Tube for tutorials:

And thanks for coming back.

Thank you for your help. I would like to clarify that the temperature drop is quite significant. The needle on the gauge moves noticeably to the left from the center position. Additionally, I have not yet received the OBD device, so I am currently waiting in order to begin troubleshooting the issue. Thank you very much. I will follow up once I receive the OBD.