Cabin temp issues

[daveabra]

Hi. Thanks for reading my post.
I have a 406 hdi 90. I am having some trouble pin pointing a issue i have with the tempature of the air coming out of the heater/aircon. Firstly the air is either hot or cold. It doesn't mix at all. Secondly the auto function seems to do nothing. Although when i press the auto button, the fan slows. so appears to do something but if the air in the car is cold, and i put the temp up on the control, the fan does not increase to warm the car up. Same if the car is hot and i select a low temp. All is ok if i use manually. but if like today it is 14 outside but really sunny (so hot in the car), i have to select 14 on the control to get the ac to cut in and make the car cool.

i think a sensor is at fault but which one.
The outside temp reads 4 degrees less than the actual temp. Is this a problem?
i have cleaned the cabin temp sensor in the light fitting and so it is all nice and clean and the fan can be heard spinning. Not sure if this is at fault.
It could be the control modual itself.
I have been looking for a new cabin temp sensor so asked peugeot. They are not made anymore which is annoying. But the chap did say there was another temp sensor behind the control modual. Is this true.

So my question is. Which thing is at fault.

Any thoughts would be appreciated.

Thanks again.

David

[gumby6371]

The cabin temp sensor is under the interior light assembly, it gathers dust easily in the air sampling fan. A paint brush and a gentle hovering usually does the trick.

[steve_earwig]

He already cleaned it.

I can't find another temperature sensor in the wiring diagrams, I thought there was another one somewhere but...

You know, I think mine maybe doing something similar but I'd put it down to maybe needing a regas or perhaps even forgetting how it actually works because I don't drive it enough

[benczuk]

I have this issue, had it since I got the car. I ran it on PP2000 and all the sensors show sensible values but the heater continues to ignore them ( reading of 12 degrees in the car, engine warmed up, control set to 22 flap position remains on cold, reading 24 in the cabin, control set to 18, flap remains on full hot )

I sourced a replacement control panel (thanks Kelv) which seemed* to fix it for a while but it is back to its old tricks again. The system only has 3 positions as far as I can tell on PP2K hot, cold, and mix. Sometimes I can get by leaving it on 24 which seems to make it stick at mix, but most of the time I have to stick it up to 30 to get noticeable heat, then back to 14 when it gets too hot. If I don't go to the these extremes and drop from 30 to 20, it just sticks on hot.

The latest theory is that the actuator/flap is sticking, and will only move when asked to go fully one way, rather than half way. The actuator test in PP2K seems to only move it all the way, top to bottom, with a note when it is in the middle, rather than hot [stop], middle [stop] cold [stop] so I cant actually test this and I haven't had the inclination to take the dash apart to try a replacement motor / test how free the flap is. This would make sense, if it has only 3 settings, as it must dance quite a lot to keep a stable temperature.

Auto "not blowing much" seems to be the norm. It seems to not like making a racket and would rather warm you up slowly (though I may yet be corrected on this )

PLEASE report back if you manage to fix it!

[Welly]

The air con evaporator and the heater matrix are in one big box and constantly running (unless your a/c if goosed) and the climate control uses an air flap (s) to control what comes out of the vents. The system looks at outdoor temp, cabin temp, coolant temp and sunlight intensity and uses all these signals to achieve the cabin set point as quickly as possible.

The 'Auto' in heating mode is very sedate, it's effectively waiting for the engine coolant to heat up but even then you will never get 'blasted' with hot air, this would be rude, instead you get drizzled with pretty damn hot air (over 50 deg C) I always found the heating to be quite good despite wanting/expecting the air flow to be stronger.

The 'Auto' in cooling mode only comes into its own when the outside temp is 20 deg C or above, THIS is when you'll get the fan speed going nuts trying to lower the cabin temp quickly.

Clearly if the actuators/flaps are not functioning the result will be weird fan speeds and temps.

[nutski]

When i got my current Coupe it was either hot or cold with no mixing it all, I swapped over the interior sensor and also control panel with no change to how it worked, in the end i found a setting in PP2000 where there were two modes of operation for the system, I changed it and it's been fine ever since.
(I'll have to load up PP and remind myself what option it was)

I did test it on another 406 where i changed the modes and effectively recreate the same problem.

[daveabra]

Thank you for your posts. I am current waiting for a new wing mirror to arrive so I can rule out the outside temp sensor. I am hace trouble finding an inside temp sensor as they are not made anymore. I did try disconnecting it to see if that helped but no luck. Wierd thing happened in the last two days. Ac worked on way home from work. Temp sensor said it was 15 outside which was nonsense. Had ac set to 14. Then yesterday similar temps but no ac. Very annoying. What systems are you referring to which need looking at.

[PeterN]

If the outside temperature sensor is not giving a correct reading, that will give all sorts of strange effects, I had this problem on my C5, worked fine after I replaced it - apart from the temperature sometimes staying at max on the passengers side, that can usually be fixed by turning it to max and then min again. That's not something that afflicts 406's though.

Peter

[daveabra]

If the cabin sensor is unplugged and it made no difference to the performance of the cooling, would that suggest it has a part toplay in this.

[daveabra]

Hello again. So my new wing mirror with ambient temp sensor arrived and is fitted. First thing it shows is that the temp is 21 degrees. I think this is to high. The one I took off said it was 10 which is also wrong. But it proves one thing. The outside temp does make the ac work. So my question is. Is there something which collates the data from the senors and uses it to alter temp. Any thoughts would be great.
dave

[PeterN]

I don't know exactly how it works but on my C5 you could only get maximum heat or nothing so it obviously uses the data from the sensor to determine the settings. Once I replaced mine it worked fine only I just replaced the sensor not the whole mirror.

Peter