CABIN HEATER NOT WORKING!

W

Whyte3237

Member
hey all,

The other day, due to the cold weather, I decided to turn the climate control on. On doing so the bars went up to indicate the speed of the blowing air. Eventually these bar slowly but surely went all the way down till off and no air was being blown out the vents!

I’ve tried manually adjusting the speed but regardless of that no air is blown out the vents and the bars slowly but surely decrease till fully off and only displaying a temperature on the display.

Any reason why this is happening?

I have also noticed my temp gauge barely reaches 70degrees. I have a suspicion it is either the temp sensor or the thermostat. Would these effect the blowing of the air out the vents? I’ve also heard about the AUX heater or webasto heaters failing? Could that be it? It’s not a big deal to me but I deifnently want to get it fixed considering the current weather conditions!

Vehicle details:

2003 1.4TDI 75ps.
 
It is likely to be the thermostat.

If the system senses that the engine is not hot enough to warm the cabin it reduces the fan until it is at the right temperature.

On a cold morning you will always find that the “Auto” setting will start off with virtually no fan and only start blowing when the engine is up to temperature.

So I would recommend that you replace the thermostat.

Steve B
 
Whyte3237 said:
Surely though when the engine is at the right tempterature the fans should work in essence, right?
Click to expand...
But if it is not getting above 70 it is not getting to the right temperature, it should be 90.

It will not blow if the heat from the engine is not warm enough to increase the cabin temperature to the selected heat.

Steve B
 
Okay I’ll give changing the thermostat a go and keep you updated on whether it fixes it. Is removing the coolant pipe that goes to the thermostat housing a necessity or is it a case of just un-doing the two 10mm bolts taking the old thermostat out and replacing with the new one?
 
Also one thing i did forget to mention is the car has always, since I’ve had it, read at 60-70degrees but the cabin heater used to work. It just decided on day not to...
 
Perhaps the temperature sender has coincidentally failed too (Very common).

Remember that the one temperature sender (the green one) has TWO circuits, one for the ECU and one for the dash gauge. and so it MIGHT be "telling" the ECU that it even colder.

Any hesitation to start when warm?

Steve B
 
Whyte3237 said:
Okay I’ll give changing the thermostat a go and keep you updated on whether it fixes it. Is removing the coolant pipe that goes to the thermostat housing a necessity or is it a case of just un-doing the two 10mm bolts taking the old thermostat out and replacing with the new one?
Click to expand...

on the TDI the only tricky part is getting a spanner to one of the bolts (due to the proximity of the alternator mounting.
Try to get a good quality thermostat, you don't want to have to replace it for a while.

That should give you a steady 90 on the gauge and while the coolant is empty (ish) it is worth replacing the temp sender at the same time.

Steve B
 
Birchall said:
Perhaps the temperature sender has coincidentally failed too (Very common).

Remember that the one temperature sender (the green one) has TWO circuits, one for the ECU and one for the dash gauge. and so it MIGHT be "telling" the ECU that it even colder.

Any hesitation to start when warm?

Steve B
Click to expand...
Not really, an ever so slight extra turn over here and there but that was in particularly cold mornings. Apart from that it usually is very instant!
 
same problem. I am also suspicious of temp sensing or sending as experienced hot starting problems. Thermostat was replaced last year. no fault codes. but CC not working as in fan not kicking in. Has anyone had the diffuser/resistor for the fan fail? I know that can sometimes mimic this sort of issue? as in no fan running
 
It is more often the fan itself.

Not that easy to get at but not impossible, worth seeing if you can (with the ignition OFF) try and spin it through the recirculation opening under the passenger dash by the floor.

Steve B
 
The fan fail shows on the climate control as the fan speed indicator rising to whatever it is set to for a short moment and then dropping to nothing with no air having been blown. Turning on and off will do the same. At least that’s what happened to mine.
Replacement fan and all was good.
It’s not too bad - glovebox off. Tufty did a pictorial tutorial which shows the hard to reach top screw where you need to go through a structural member in the dashboard with a LONG extension.


Sent from my iPhone using Tapatalk
 
I got a second hand on from A2Steve and fitted it. I'm a mechanical numpty and it didn't take long and worked perfectly... therefore it's easy. cost wasn't much - can't recall. Certainly cheaper than dying of hypothermia.


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Wow, that's a coincidence, I was just looking for advice for my cabin heating / temperature gauge issues.
I have had an issue that the temperature gauge on the dash has been intermittently not moving - it used to go straight to 90 after a time driving. Occasionally, seemingly randomly, it will still move, but not reach 90.

A garage checked the temperature sensor and said it was good.
It was suggested that it was a cabling issue, but I was not that bothered if it was just affecting the gauge.
I even asked a garage to check the thermostat while replacing the alternator, but they said that it was un-necessary according to the symptoms. They suggested a cabling issue too.

I have recently had the temperature on high to try to dry out the cabin after getting frost on the inside of the windscreen so know that the blower was working fine then.
Sometimes, recently, the hot air coming through the vents was unexpectedly hot while the climate control was set to auto and temperature set to 20 degrees.

Occasionally the engine would loose power as if it was overheating or something, but rectified itself after pulling over and switching the engine off and back on again. With the temperature gauge not working I could not conclude that the engine was actually overheating though.
No warning lights on the dash either.

Last night I drove home and could not get the windscreen de-misted.
Put the temperature to high and fans to high - no heat through the vents.
Checked the coolant level, it was OK.
Checked the blower fuse (16), it was OK.
When I cracked open the windows while driving I could feel some warm air coming through the vents.
I had a fiddle with the heating controls this morning after driving ~25 miles and the fan speed indicator bars stay at full when I set the fan to max speed, but no air coming through the vents. I could hear the flaps moving OK when switching demisting on and switching heat between the dash and the foot well etc.

Reading the above posts I am still not sure what might be wrong.
Sensor?
Sender?
Thermostat?
Fan?
Cabling?
Several different things?
 
You say you were not getting heat through the vents, but could you feel any forced air? If so then I would assume that the flaps are set as they are moving the air around but it is not heated. See if the engine comes to temperature at standstill as driving it will increase the time it takes to come to temperature (if at all). The thermostat has not been checked so it could be an issue there or an issue with the control unit if you had hot air randomly coming through when not set on hot.
 
The sensor for the temperature that will affect this has TWO circuits and even if the temperature gauge was showing perfectly correctly it still might be the cause. One circuit operates the gauge and the other circuit (in the same sensor (4 wires) feeds the temperature to the ECU to enable it to make decisions on what to do about fuel mixture and also the climate fan etc.
These sender are known to fail.

My advice is (as I have said) that basically your temperature gauge should be reading 90 when the car is fully warmed. Yours is not.
So the engine is either running colder, which is matching the symptoms you are having, or the sender is broken.

But replacing both at the same time makes sense here no matter what the Fan is doing (in my mind).

Eliminate the less costly and easier to fix options first and since there are many A2s that have a broken sensor and/ or a failed thermostat it will not be a bad thing to "refresh" those anyway. THEN you can have a car that runs at the correct temperature and with the gauge showing that and so then you can look at other causes if you still have the problem.

Eliminating possible and/or likely causes is not a bad approach.

Steve B
 
Neil50 said:
You say you were not getting heat through the vents, but could you feel any forced air?
Click to expand...
No forced air, hot or cold.
Neil50 said:
If so then I would assume that the flaps are set as they are moving the air around but it is not heated.
Click to expand...
Flaps are moving but no air movement.
Neil50 said:
See if the engine comes to temperature at standstill as driving it will increase the time it takes to come to temperature (if at all).
Click to expand...
How do I check if the engine comes to temperature if the gauge only works intermittently - I feel that I can't rely on that to tell me the engine temperature. One garage checked the sensor and said that it was working OK though.
Neil50 said:
The thermostat has not been checked so it could be an issue there or an issue with the control unit if you had hot air randomly coming through when not set on hot.
Click to expand...
By the "control unit" what do you mean?
 
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