Hi guys, my AUM 20VT just developed a new habit.  When I start it, after 5 min I turn on the heating, for 15-20min hot air is coming out.  After that, the air coming out is cold (!)  Any guesses?  And I think some times I see the outside temperature going up to 16C, when the weather outside is no more than 8C. 

 

Any guesses?

When you have problems with internal heaters going cold, it's usually more often than not an air lock in the cooling system.

 

However, combined with the fault you are reporting of the external air temperature mis-reading, it may be more than that I guess.

 

You need to go back to basics to diagnose this.

 

Firstly - has any work been done to the car - AT ALL - prior to this problem? If yes, please give details.

 

If no - then it may be due to the external air temperature sensor mis-reading as you say. Simple way to check this is to run the heating in manual, and not use the climate control mode, which will utilise the external and internal temperature sensors.

 

Put the system into 'Econ' mode. Then turn the temperature control up to 'High'. Run the car....has this solved the problem, or is it still going cold after a while?

 

Let us know

well, the battery went dead and it took me 20days to change it.  That was the only thing I can think of.

 

How do you run the heating in manual? 

What I usually do is set the temp I want, e.g. 24C, and then set it to 2 bars, and then leave it there.  After sometime the air goes cold.

 

Will try the ECON thing you said in the weekend and will let you know.

Must say have not checked the fuses due to poor weather

it is still going cold after a while still...

hey theo,

 

well have you got any misting in the car, is your coolant level corect or low, can you see any leaks in the lower front footwells?

(check these to eliminate heater matrix leak)

 

does the car get up to normal temp ont he gauge?

how old is the thermostat and CTS (coolant temp sensor)

does the fan blow on all speeds?

What happens if you increase the set temperature to, say, 27 degs after you notice it going cold?

The reason I suggest this is because of the way climate control works. Once the set temperature has been reached, it will blow cooler air out of the facia vents than footwell vents; more so if the sun sensor on the dashboard detects sun heating. You may just need to set a higher temperature request.

I have mine set at 24 normally but increase it as necessary in winter. Try it and let us know. If the heating comes back with a higher temp set, then we can eliminate air-locks etc.

24 degrees is enough for me to get heat stroke

24 degrees is enough for me to get heat stroke

 

Its just a number as a guide, just like your heating thermostat at home.

 

I prefer to set for warm feet and cool head using the other controls so 24 is not what you get all over. 

well, Oet talked about coolant, I know I am missing some because every now and then the handbrake light comes on and beeps.  Shell near my house ran out of G12, so will try again tonight and will let you know guys.

 

no matter what temperature I set it to, after a while it comes out cold even though the desired temperature is not reached in the car.

 

and since we are on it, some weird spongy bits are coming out of the centre vent that blows on the windscreen.  Cabin filter is brand new.  It seems as if something spongy is in the way of the air blowing in the car and little by little is getting destroyed and the bits are coming in.  It was doing that before I changed the cabin filter.

the handbrake light is linked to the brake fluid res, that only comes on if the brake fluid res is low, should have nothing to do with the coolant loss.

Are you actually losing coolant? how much?

 

does the car steam up easily?

coolant smells funny, you should notice this in the car if the matrix is leaking, plus the steaming of course.

I must admit this is a bit embarrassing, somehow I thought that when the exclamation mark bleeps and there is a sound, it was the coolant. 

So to start with I will check the brake fluid.

Then I will check the coolant.  I did have a look the other day and it seemed ok and within the min and max lines.

don't worry, just check your brake fluid too then, and make sure you put in the right stuff.

there is always mist!

 

brake fluid is ok, it just bleeps when i go uphill(!), a bit above the minimum line, will put some more in (ferodo 5.1)

the coolant is fine as well, well above the minimum line.

 

I dont think anything is leaking, however the car steams  up.  Tomorrow will check the carpet all around the car too.

 

any other ideas why the hot air turns into cold after 10-15min?