Car not getting hot

[ti rich]

In this cooler weather i have noticed that despite a 40 mile drive my car isn't getting up to temperature. It stays around the 50 point - is this normal??

I do take it easy and not a lot of traffic on my daily drive by even so it doesn't appear right to me.

[gregpawley]

I have similar with mine, again a 2.0 TDI S Line, seems so to take about 15 miles before registering any temperature. after a while will eventually read the 4 bar normal reading however if you turn the heater onto max it drops the temperature to the bottom of the scale.

Another thing is the auxiliary heater how effective are people finding it? after a couple minutes from the cold, the heater seems to take the edge off the air coming from the vents, although not what you would call warm. and to get any decent flow have to turn the fan speed to manual and max, or increase temperature from the 22C normal to the Hi setting.

[dgarside]

Nothing to add other than I'm experiencing exactly the same. Was going to check with dealer when I could get down.

[gregpawley]

Think the effectiveness of the cooling system and the engine so efficient is the major cause. Even before this recent cold snap turning the heater onto full would bring the temperature gauge down to the minimum quickly.

Would be keen to know what the dealers say

[fayraz]

I have the same issue.

[a8 tech]

Units are warmed up in two phases:3.0l V6 TDI CR (CDUC / CLAB)

my understanding of the new systems AND MAY NOT BE 100% TRUE

coolant is stored in the engine from cold with no or only internal engine circulation to produce the heat required for fast cabin temp hence the dash is reading low until the temp is achieved and coolant flow now started as per normal, flow through to the coolant sender and thus the gauge now moves to normal operation temp as per coolant management.

Phase 1( STATIC COOLANT)

.. The stationary coolant produces a faster
increase in temperature within the engine
thereby reducing friction losses. The injection
cycle can also be optimised
.. After the faster heat-up phase, a transition is
made to phase 2

Phase 2 (START OF COOLANT FLOW)

.. The hot coolant is now used to quickly heat the
gear oil in the heat exchanger. For this purpose,
the heat flow is diverted by an electrical
switching valve actuated by the gearbox control
unit. To avoid excessive thermal stresses and to
prevent the hot engine coolant from being
circulated completely at once (this would
impair the engine's friction properties), the
mixing phase is cycled

.. If the customer wants the cabin to be heated as
quickly as possible, heat is transferred as
quickly as possible in order to heat the vehicle
interior. In this case, the coolant is not
stationary in the engine

.. However, the gear oil is not only heated, but
can also be cooled as required. Since no
separate cooling circuit is available, the gear oil
is cooled down to the temperature level of the
engine cooling circuit. The coolant flow to the
gear oil cooler is shut off by the coolant flow
control valve during the optimal gearbox
temperature phase


So in short all new platform engines are thermal managed to direct heat (if you demand it )to the cabin thus actual engine coolant readings will be lower due the demand of the driver in warming your little feet's

Actual readings at the dash are true but using more ecu trickery

new stuff

2 sensors

G694 Temperature sender for engine
temperature regulation

G62 Coolant temperature sender
Gear oil heating / Cooling

Heating shut-off

Mapped engine cooling thermostat
(650C-900C)

Oil cooler bypass thermostat

[gregpawley]

Hi a8 tech, thanks for the technical breakdown.

So what this boils down to (pardon the pun), is now there is some electronic trickery in the form of actuated valves that now replace the mechanical thermostat of old. And in this weather where the user will probably have the heater set to Hi this draws the coolant away from the engine extending the cycle obtaining the normal operating temperature?

What we see where the car not reaching the normal temperature is the by-product of the effectiveness of the heater matrix removing heat from the coolant circuit, and the efficiency of the engine not generating heat.

I see you have quoted 3.0l TDI engine, would this also be the case as for the 2.0l TDI as I believe most of us in this thread have?

Greg.

[a8 tech]

Yes, I will of course find the true answer and for 2.0 common rail as well

[ti rich]

Thanks, that really explains a lot. Time to turn down the cabin temp if you want to save on the MPG!

[gregpawley]

Just done a little experiment, started the car from cold (ambient 7.5C) with the aircon turned off. drove 2.0 miles to the dual carriageway then set cruise to 70MPH, after total of 3.0miles 0.06 hours the second bar on the temperature gauge lit, 5.2 miles and 0.08 hours the third bar lit and at 6.1 miles 0.09 hours the forth (90C) lit.
I then turned the aircon on with the fan and temp set to max, after a minute or two the temp dropped to the third bar, but did quickly go back to 4, it seemed to stay there then happily for the duration.
As soon as I pulled off the dual carriageway and back into town driving it dropped to three then two bars. I parked up with the engine idling and with a couple minutes dropped to the minimum one bar.

So it looks like that our engines are warming correctly, however in normal morning start stop driving in towns with demand on the heater is preventing (delaying) them getting to the normal operating temperature.

So the choice is heater off and let the car warm, or heater on and let the car suffer...

Greg.

One thing I did notice with the heater and heated windscreen off, stopping at traffic lights within a mile of starting the the start stop kicked in, the drive select was set to Auto for this.

[a8 tech]

If you have demist on start stop is inactive

Start stop looks at cabin temp and outside temp amongst other variables so if windscreen demist on start stop will not activate as it presumes your vehicle is cold also with aircon on it will again be inactive as it presumes your hot lol

Lots of variables for start stop

[a8 tech]

At outside temperatures under 5°C the engine temperature fluctuates according to the display in the dash insert between 50 and 70°C or till the coolant temperature reaches 90°C. The phenomenon occurs mainly when driving at low engine speed


Because of a very good effectiveness of the engine in low rev range, little engine heat is passed on to the coolant. At low outside temperatures the coolant temperature does not reach 90°C. If the heating is used, the coolant loses further heat depending on the blower level. As a result, the coolant temperature can fluctuate between 50°and 90°C.



Below an outside temperature of 5°C and a coolant temperature of 70°C the standard PTC auxiliary heater is activated, to heat the interior. The best effectiveness of the PTC auxiliary heater is achieved when the temperature is on 22°C and the air conditioning on "auto".


Sent from my iPhone using
My fat fingers

[robbyg]

auxiliary heater? Whats that?

How does all this relate to "residual heat" which is part of the 4 zone climate pack? I assumed that uses some sort of heat store or uses the AC as a heat pump like my volvo does to warm the cabin up faster than by engine heat?

[dgarside]

Not using E'fficiency mode and sticking in Auto till it warms up makes a big difference on my journeys. E mode was taking an age to warm up nearly an hour and 30 odd miles at times.

[fayraz]

Not using E'fficiency mode and sticking in Auto till it warms up makes a big difference on my journeys. E mode was taking an age to warm up nearly an hour and 30 odd miles at times.

I have mine on Econ mode all the time I will try mine on Auto mode and see if it warms up quicker.

I thought Econ mode was supposed to be more fuel efficient?

[shabazmo]

auxiliary heater? Whats that?

How does all this relate to "residual heat" which is part of the 4 zone climate pack? I assumed that uses some sort of heat store or uses the AC as a heat pump like my volvo does to warm the cabin up faster than by engine heat?

From my understanding, when the stop function operates, the engines continues to pump water from the hot engine into heater matrix therefore continuing to warm up the car by using the stored heat in the engine. Those cars without the 4 zone system can only use the risidual heat in the heater matrix which would last only a minute or two.

[nealeb]

I have mine on Econ mode all the time I will try mine on Auto mode and see if it warms up quicker.

I thought Econ mode was supposed to be more fuel efficient?

Maybe it's because the aux heater uses electrical power that must be made up by using engine power later, and Audi have decided that this uses more fuel overall than having an engine that warms up more slowly? Interesting comments, though, and it rings a bell with something that I read in the manual. This A6 seems to warm up at about the same speed as my previous A6 (C6) but maybe that's because mine is always in Econ/Efficiency mode. Must try something else sometime!

[johnsimcox]

Maybe it's because the aux heater uses electrical power that must be made up by using engine power later, and Audi have decided that this uses more fuel overall than having an engine that warms up more slowly? Interesting comments, though, and it rings a bell with something that I read in the manual. This A6 seems to warm up at about the same speed as my previous A6 (C6) but maybe that's because mine is always in Econ/Efficiency mode. Must try something else sometime!
Auxiliary Hester and Residual Heat are different. Auxiliary Heater is in effect a diesel powered boiler (so has no electrical drain) that operates to speed up the engine heating and cabin heating process when the external temperature is cold. Without this it would take ages for the car to defrost on an icy morning. It can be turned off via the MMI. Residual heat is a function of the 4 zone AC system on the C7 (also works on the 2 zone digital display system on the C6). After turning the car off pressing and holding the AC or Econ (button name varies between different systems) will cause the fan to reactivate and continue to heat (or cool if the exterior temp is higher than the car) the car for a period of time.

[shabazmo]

[QUOTE=a8 tech;696970]Below an outside temperature of 5°C and a coolant temperature of 70°C the standard PTC auxiliary heater is activated, to heat the interior. The best effectiveness of the PTC auxiliary heater is achieved when the temperature is on 22°C and the air conditioning on "auto".

What is the PTC aux heater, how does it work and is it electrical. I have it set to on on the MMI, bur can't notice ant difference when I start the car from cold with the aircon on and without the aorcon on.

[johnsimcox]

[QUOTE=a8 tech;696970]Below an outside temperature of 5°C and a coolant temperature of 70°C the standard PTC auxiliary heater is activated, to heat the interior. The best effectiveness of the PTC auxiliary heater is achieved when the temperature is on 22°C and the air conditioning on "auto".

What is the PTC aux heater, how does it work and is it electrical. I have it set to on on the MMI, bur can't notice ant difference when I start the car from cold with the aircon on and without the aorcon on.
Not sure what the PTC piece is that A8 Tech refers to but the Auxiliary Heater controlled via MMI is in effect a small version of a domestic central heating boiler that burns diesel and heats the coolant so that the heater for the car is effective sooner and therefore windows can be defrosted and the car warmed up. This is one of the reasons why the fuel consumption of diesels is worse in cold weather. Interesting that it is most effective when the temp is set to 22°C, I'll have to try that as I usually have the temp set lower than that

UPDATED
Just been out and tried the car at a higher temp and noticed no difference in the speed of the car warming up so not sure if the 22°C bit is true ands amy actually require it to operate longer as it will take longer to get the car to 22°C than to say 19°C and thus take more heat out of the coolant system and slow down the overall process of getting the car and engine up to temperature. Also noticed that when you have the windscreen defrost activated the a/c comes out of Auto so again the efficiency of the auxiliary heater seems unlikely to be directly affected by this setting although the speed of warming the entire passenger compartment will be enhanced with the system on Auto as it will optimise the airflow

[foxy367]

I'm a bit confused here. My simple engineer mind says that the guage is irrelavant in terms of the actual engine temperature. This guage refers to 'coolant' temperature and that oil temperature is completely seperate. Although the coolant temperature is lower the engine shouldn't be any slower at getting to temperature due to the effects of combustion. In colder weather it is obvious that the coolant won't be as warm as the ambient temperature is lower. However by turning off heaters and AC and the like this won't affect the engine getting to temperature as the combustion process will in effect heat the block which in turn heats the oil it is not the water in the coolant which heats the engine.

Back in the day if your car was overheating you could turn the heater on inside the car which would lower the coolant temperature and help prevent your coolant from boiling. There is clearly electronics at play these days but the principles are the same. By increasing the cabin temperature the coolant temperatrure will drop as you are tranferring the heat 'contained' within the coolant system.

For info I drove 40 miles today at temperatures between 0 and 2 degrees and the coolant temperature sat somewhere between 50 and 90. The internal temp was set at 25.

[KAM]

Not sure what the PTC piece is ... At last, something I know about! PTC = Positive Temperature Coefficient. This is used as short-hand for a type of material whose electrical resistance rises rapidly with temperature. Lots of stuff has a +ve temp coefficient for resistance, but some have a very high coefficient. This makes them very suitable for rapid heating applications. To start with, low temp results in low(ish) resistance. However everything with resistance produces heat, so the PTC item heats slightly and its resistance jumps up. Higher resistance results in more heat which produces a higher resistance which ...
So this "PTC unit" must be battery-powered, even if it is used for only a brief period of time to get things up and flowing nicely.

[fysmd]

Units are warmed up in two phases:3.0l V6 TDI CR (CDUC / CLAB)
...
So in short all new platform engines are thermal managed to direct heat (if you demand it )to the cabin thus actual engine coolant readings will be lower due the demand of the driver in warming your little feet's
...
found a little vid which explains this also:
Innovative Thermal Management > Efficiency technologies > Audi Worldwide (http://www.audi.com/com/brand/en/models/efficiency/efficiency_technologies/energy_management/thermal_management.html)

[Thriftmeister]

I'd like to resurrect this thread, I hope that's OK.
I'm new here, I was searching for answers to the slow warm up issue and found you all. I have just collected my C7 2.0 TDI Avant having handed it to the "experts" to sort it. Some great stuff here. I appear not to be alone with my issues. Oddly I didn't notice these issues last winter but it I think it wasn't as cold.

What have I learnt?
Firstly, Audi said it was a faulty stat. Well, after a 29 mile trip yesterday morning there is no change. If I turn the heater up above 22 the temp drops to 2 bars and stays there. I drive at 70mph/2000rpm on the motorway and yesterday averaged 49mph for the 29 miles so not exactly dawdling.
If I turn the heater off, and I mean completely off it warms up in 6 miles with temps of about 5 degrees. Turn the heater on and it drops back down.

When my C7 was in the garage they gave me an A6 Ultra s-tronic Avant. I scraped ice off the car and drove away. It was warm in 4 miles and stayed there. After sitting for 4 hours it was warm in 2.5 miles and the heater was on at all times. Does anyone know if the 190 engine has been modded? The garage didn't know.

As for Aux heaters, I doubt anyone with a UK spec car has one. What we all have is a supplementary heater, an electrical element in the heater matrix which helps warm your toes/clear the screen when the engine is cold. It is standard fit on the diesel. Question is how do I confirm it works? When should it work? Is there a simple test? The car does produce heat reasonably quickly but so does my other car, a 1.4tsi Golf. Would the dealer have been able to test it with VAG.COM OBD?

I find it is fine if the temperature is above about 9 degrees but below that I rarely see 4 bars on the gauge. True to my screen name:Blush2: there is another issue here and that is the fuel consumption rockets from 50 to low 40s as soon as it gets cold. Same commute, same speeds. What might it be doing to my engine & my DPF?

[Thriftmeister]

Wow not a single response.

Anyway, I have learnt a thing or two some of you may be interested in.
The new 'stat has made no difference. The temperature slips back down hills even after 20 or more miles if I go down a hill or slow to 40-50. See photo.

You can see when the supplementary heater kicks in on the DIS. Go to Efficiency Program and it shows a bar graph for consumers. The supplememtary heater adds about 1cm to that graph and I can hear a relay clicking in when it switches.
In drive select efficiency mode I haven't seen it work at all even down to zero degrees. It works as I'd expect in other modes.
In drive select - systems, scroll to AC and if the system is in ECO it rarely works unless the cabin temp is selected to Hi (max). In normal and intensive it works even with 20 degrees selected.

Now the shock was fuel consumption. In efficiency mode below about 6 degrees the consumption for the first 10 or more miles is about 20% higher than on a warm-ish day. But select AC to normal and drive select to Auto and consumption improves markedly. Not warm day levels but far better than in so called efficiency modes!

In efficiency & ECO modes & cold weather the engine takes anything up to 15 miles swift driving to get warm. In other modes it's more like 6 to 8 miles. Efficient?

Any other ideas how to warm-up will be much appreciated.

[ukgroucho]

I'm not sure I can really add anything to this other than to comment on my amazement that a car being driven "normally" is not getting the coolant up to a normal operating temperature. Now I take onboard the comment from a previous post that coolant temp as indicated on the dash may not reflect oil temp - which is the important bit - but my experience is that they are inextricably linked.

My BiTdi fairly quickly shows water temp climb to 90C - even in winter. In summer it gets there in 2 or 3 miles (fairly gentle B road stuff) and in winter it is 3 or maybe 4 miles MAX!. The oil temp lags behind it - so once water reaches 90C it takes a while to see even 60C on the oil - usually 1 to 3 miles and then it climbs into the 90C+ range in a pretty linear manner.

I know this because I was fortunate to have Splash visit me with his laptop and VCDS and we enabled the "lap timer" function in the MMI (colour DIS).

I really do not need a lap timer (never used), the turbo boost gauge is interesting, the little digital MPH readout is nice .. the gear shift indicator bars ala F1 race car are amusing (when you are in manual shift mode)... none of that really matters 'cos the icing on the cake is you get a lovely little digital oil temp readout.
If you're really interested in what is happening inside your engine then find someone with VCDS (and check the sticky top of the forum for instruction) and get it switched on.

I really miss the battery voltage and oil temp gauges that my old Audi 80 Avant had in the dash :(

[EssexGonzo]

If it helps , my 13 yo A2 Tdi and my C6 2.0 behave in the same way and have diesel powered aux heaters too. Someone once said that the engines are thermally efficient by way of explanation.

I've just done a 45 minute stop start drive including 3 miles of 60mph dual in the A2 and the temp gauge is barely off the bottom . 3 deg C . Cabin nice and toasty though.

[ukgroucho]

I've just done a 45 minute stop start drive including 3 miles of 60mph dual in the A2 and the temp gauge is barely off the bottom . 3 deg C . Cabin nice and toasty though.

I don't recall that behaviour in the 1.4 TDi A2 that we had for 8 or 9 years.... I'd have noticed.

[EssexGonzo]

Fairly widely reported on the A2 forum, hence most Tdi models have the aux heater fitted.

[Thriftmeister]

Very enlightening info thanks. Makes a change from the "please can you help me decide which of the 50 shades of Audi grey shall I specify on my next car?":aargh4:

As I said above the Ultra I borrowed warmed up almost like a petrol. 4 miles at 0 deg. Any techies know what's changed?

I do not have a diesel powered aux heater. I asked at my local main st(d)ealer and they can't recall ever specifying it as an extra on a new car. They weren't around as long ago as A2 production days. They weren't bright enough to know whether it is standard on any models but it certainly isn't on my old 2.0 TDI A3 my 3.0 TDI A5 nor my current 2.0 TDI A6.

I love the car, and as it's leased I don't care if it dies, but as an engineer I hate to run something that just doesn't seem right. And at this level of luxury I shouldn't have to sacrifice cosy toes to heat the block.

[johnsimcox]

Very enlightening info thanks. Makes a change from the "please can you help me decide which of the 50 shades of Audi grey shall I specify on my next car?":aargh4:

As I said above the Ultra I borrowed warmed up almost like a petrol. 4 miles at 0 deg. Any techies know what's changed?

I do not have a diesel powered aux heater. I asked at my local main st(d)ealer and they can't recall ever specifying it as an extra on a new car. They weren't around as long ago as A2 production days. They weren't bright enough to know whether it is standard on any models but it certainly isn't on my old 2.0 TDI A3 my 3.0 TDI A5 nor my current 2.0 TDI A6.

I love the car, and as it's leased I don't care if it dies, but as an engineer I hate to run something that just doesn't seem right. And at this level of luxury I shouldn't have to sacrifice cosy toes to heat the block.
But you do have the Supplementary Heater, which I understood was diesel fuelled not electric. The Auxiliary heater is only offered as an option in very cold climates, can be activated via the remote or using a built in timer in the MMI system and allows the car to be preheated without having to start the car. Also if you look at the Audi Self-Study guide (you will need to do a search as it is not permitted to place a link to it here) you will see that selecting Eco mode for the car reduces the output of the Supplementary Heater

[EssexGonzo]

But you do have the Supplementary Heater, which I understood was diesel fuelled not electric. The Auxiliary heater is only offered as an option in very cold climates, can be activated via the remote or using a built in timer in the MMI system and allows the car to be preheated without having to start the car. Also if you look at the Audi Self-Study guide (you will need to do a search as it is not permitted to place a link to it here) you will see that selecting Eco mode for the car reduces the output of the Supplementary Heater
Works at or below 7 deg C and on the A2 sounds like a little turbine, also slightly extra dieselly smell outside. In the A2 disabled if Econ button is lit.

[ukgroucho]

Definitely did not have the "little turbine" affair in our A2 - but maybe it was not available on the very first ones... ours was an early one on a Y plate.

[Thriftmeister]

I'm not sure about the A2 but the A6 supplementary heater as in the MMI is definitely electric. Attach an ammeter & one can see the current drain when you hear it start & there's a click of the relay too. It's effectively an immersion heater in the heater matrix. Being fully automatic it seems to switch off when the engine produces some heat but then the heater matrix takes all the heat the engine can produce at low loads so stays cold.

Does anyone know if there is a separate thermostat in the heater circuit? If so could it be that which may be faulty on mine? Stat open so supplementary heater not needed, so car stays cold???