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Heating not working properly

Old 01-21-2013, 01:52 PM
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Default Heating not working properly SOLVED

I have a weird issue with my 2006 W12.

The fan motor never goes over 5-6 in auto mode (max is 12), and i've noticed that the car is not warming up as fast as it could, especially now as the outer temp is below freezing point.

Today i had to take more clothing on, while driving 150km in an outside temp of around -15c.

Luckily i had my diag with me, and took some readings of the ac control panel.

If i understood right, the roof sensors were reading 19 and 20c in the front, and the sensor in the panel itself was reading 16c. I was asking for 28c. The fan was at speed3 on auto.

In the first couple ten kilometers the windshield centre vent was blowing arount 10-15c air, the floor around 40c, and the middle vents 30c.

If i put the fan blowing faster, the air coming out would only be switched to colder.

No matter if i asked for 20 or 28c, i wouldn't get any hotter air out.

The engine was of course at over 90c.

The weird thing was that the rear heating wasn't blowing any warm air at all...

could i have something clogged up in the system, as i got no sensible faultcodes, apart from right and left footwell heater faultcodes (these seen to be "normal" on our cars), and heated windshield (haven't got one)

What could be wrong?

The fresh air filter in front of the windshield is one month old, so that's not clogged up.

Last edited by volvopentaman; 03-03-2018 at 02:03 AM.
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Old 01-21-2013, 02:16 PM
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Default How about the basic (aka complicated) heater regulator valve?

Remember in the old days when heaters just had a cable that pulled a simple valve open and closed that was in line in the heater hose? If that valve gets stuck or clogged some, it would restrict the hot water flow. Since you have an engine at op. temp (90+ C) and report less feeling of heat with more blower fan speed, that's why I'm thinking the heater water regulator set up. On newer cars like the D3 of course (or anything post D1/C3 I think) the old mechanical set ups got superseded by electrical controls.

If I remember, you even have a W12 like me so I have better familiarity than I would w/ a D3 4.2. The valve that serves that function is under the engine plenum cover at the rear, just to the left (U.S. or European non-UK passenger side) of the HVAC air filter if you are looking underhood. You will see water lines going to and from it--which are heater related of course) and a few electrical plugs. IIRC it has two circuits for the passenger and drivers separate sides. On at least the W12 there is also an unusual one way flow element to it that is interrelated to the after run water pump the car uses to keep the engine cool. They don't want hot water going through the heater core w/ the afterrun pump on a warm day because the cold AC related panel would condense out a bunch of water and then tend to fog the windshield on start up. If you ever see a fogging windshield on a warmer day by the way, a possible clue this part is acting up. I haven't ever had to diagnose it beyond a tiny physical leak at a clamp, so you would need to check the service manual or start playing with it, especially obvious stuff like the electrical connectors, anything VAG COM might report about it, etc.

Aside from that diagnostic, I might say the basic motor thermostat set up as a possible, but since you report good engine op. temps, that seems less likely unless there is something specialized to that set up also relating to the heater. But per the above about the specialized flow features they already have in the W12, I expect it is handled by the heater valve set up.

Later edit: If it helps by the way, the W12 HVAC related concepts are pretty well discussed and explained in the W12 motor SSP, at least the US version--I know there is a Euro/German version too that if anything seems yet more comprehensive when I have seen occasional reference too it. The heater regulator (and the non return valves) are explained, plus other overlapping things like the after run pump, the auxiliary water pump, the water temp. sensor, etc.

Last edited by MP4.2+6.0; 01-21-2013 at 02:32 PM.
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Old 01-21-2013, 03:32 PM
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Could it be that you have some air in the system?
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Old 01-21-2013, 04:46 PM
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It could also be the pump on the HVAC system. If this pump stops, the flow through the heater cores would be limited. There is a separate fuse for the pump and valves, which also controls the rear HVAC. Check the fuse first and see if this might be the problem.
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Old 01-21-2013, 07:58 PM
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Originally Posted by mishar View Post
Could it be that you have some air in the system?

When I did my rebuild there was an air pocket and the heater would not work well, you have to burp the system. The manual calls for a complicated vacuum thingy which I do not have, but running the car and opening the reservoir at intervals (CAREFULLY) got rid of the air bubble.
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Old 01-22-2013, 01:33 AM
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Started mysef too to think about air in the system, as i think some of the heater hoses are higher up than the engine.

I swapped the thermostat when i bought the car, soon 2 years ago, and got out maybe a cup or two of fluid. I also broke the bleeding line to the expansion tank, while digging around the manifold in the summer. And now a couple months ago, when the weather got cold, the car started to ask for fluid (because if the level is in hot weather at the limit, it will be less when the weather gets cold, because the fluid volume contracts more than the engine+hoses volumes in cold weather.

I shall vacuum out the air, by taking out all fluid and suck it in again with a vacuum pump.

Air would explain the problem, as the air coming out cools as the fan speed increases, BUT it the heat increases dramatically in 2-3 seconds, from about 40c to 15c, if i put the fan from 3->12. That seems a bit too radical for me, and i'm starting to think the air blending motor could be acting up too...
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Old 01-26-2013, 12:37 AM
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Did some research on the stuff yesterday. Tried the bleeding screw that is beside the blower motor, no air there, absolutely no air.

Then i noticed that the heating works flawlessly when the engine-preheater WEBASTO is running.

But when i drive the car, especially on highways, the temp starts to drop if i have it set around 22celcius.

When i set the temp to around 16-18celcius, i start getting some heat. If i set the temp to 28celcius, i mostly get just cold air. If i set the temp to HI, i also get cold air. If i set the temp to LO, i also get cold air.

The AC control unit sensor sees the correct temp, and also the sensors in the dash air ducts see the correct temps that come out.

The weird thing is that the air direction switches sporadically, especially often if i have the steering wheel heater on, from the windshield to the dash vents. The floor always gets warm air, but the windshield mostly cold air, except for when seldom it chooses to give me heat.

And the weird thing, is that the air direction and heat of the air is sporadically changning, without me doing anything.

The rear ac only gets cold air, no matter wich temp i choose from where, both the center, floor and rear door vents.

No faultcodes, except for missing heated windshield (i don't have that installed, and not coded, same thing with my friends 2005 A8 4,0TDI, and that works), and the normal rear footwell heater faultcodes (mostly the right one).

I wonder if i could have mistakenly coded the control unit wrong (while i was tampering with my ACC install), or done something else, because this is totally weird.

I found a control module channel map, so i know which channel does and displays what, but the problem is that I do not know what fault to search for...

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Old 02-17-2013, 12:34 AM
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Have you tried to read G150 and G151 values?

I have kind a same problem.
Left sensor reading always 20-30C* more than left one and right exchanger itself seems to be roughly.

I removed flaps for footwell heat and tried to touch the exchanger and it won' t getting all the way warm.
If i raise manually fan speed, exchanger is cooling even more.

Anyway, coolant temp withc goint to exchanger and back is the same, with for left one - so, no problem with pump and valves.

I removed the exchanger and tried to clean it, nothing- looks like have to replaced with new one.
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Old 02-17-2013, 07:23 AM
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Shall check the G150 and 151 values again, if i remember they are quite the same as is the G190 too.

The problem isn't as big when the outside temp is around 0celsius, but it takes ages to warm up the cabin compared to my volvos.

I also have the problem that if i turn up the fan, the air that comes out gets cooler.

Shall check this thing out in about a week, when i have better time after my exams coming friday.
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Old 03-03-2013, 02:39 PM
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Did a scan on the climatronic today, and noticed that the coding was atleast bogus. 87047, meaning a SWB V8 RHD model with heated windscreen and rear HVAC control. The only thing that was right about the coding was the rear HVAC control.

I don't have heated windscreen, my car is LHD, LWB and W12, is equipped with sunroof and heat insulated glass (missing from coding).

The coding that i read was 87047, and it should have been 111835.

Still, there is something wrong, the heating is now way much better, BUT the centre-vents aren't working as they should, and the front passenger-side still gets colder air.

Shall try more with the coding tomorrow, as i did an actoautor test, and all actuators seemed to work as they should, except for the centre vents, that worked the wrong way or something...
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