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View Full Version : Heater not blowing hot air & HVAC Communication error



woolveren
10-23-2013, 05:33 PM
Car is a 98 1.8t. A bit history on the heater; it was working absolutely fine early this year in spring, used to blow real hot air at high temp settings.
But now, the heater is blowing only luke warm air even at the highest ĎHIí setting on the dial. Engine temperature is coming up properly and always sits at the middle. I just came back from a 1 hr drive, but still it blows luke warm air.

Iíve recently flushed the antifreeze with genuine audi coolant and really donít think it's a clogged heater core because it was fine till some 7 months ago. Can this be caused by a temperature sensor reading bit off? I am not sure how the system does the calculation or how many sensors are used for it. I have changed the IAT(Bosch) and ECT(Genuine Audi) sensors couple of months ago. I did the on board diagnostic for the HVAC and below are the values I got; Can somebody confirm whether these sensors values are looking normal or not?

1 System malfunction - displayed as a Diagnostic Trouble Code (DTC), see chart below- .0
2 Digital value of Interior Temperature Sensor, in Headliner (G 86)- 14.6
3 Digital value of Interior Temperature Sensor, in Instrument Panel (G 56)- 13.7
4 Digital value of Fresh Air Intake Duct Temperature Sensor (G 89)- 11.1
5 Digital value of Outside Air (Ambient) Temperature Sensor (G 17), front- 12.3
6 Digital value of Outside Air (Ambient) Temperature Sensor- 15.8
7 Digital value of Ambient Temperature Sensor At Fresh Air Blower (G 109)- 17.6
8 Digital value of Temperature Regulator Flap Motor Potentiometer (G 92)- 9
45 Calculated interior temperature (internal software, in digits)- 28.1
46 Outside (ambient) temperature, filtered, for regulation (internal software)- 13
47 Outside (ambient) temperature, unfiltered, (internal software, in deg C)- 0
48 Outside (ambient) temperature, unfiltered, (in digits)- 6
51 Engine Coolant Temperature (ECT) in deg C- 90


Also, I tried to talk to the module using registered VCDS; but it connects to module, then disconnects, then connects again, and goes on like that. Finally it will show the error ďToo many communication errors to continueĒ. Does anybody know why VCDS is not able to communicate to the Auto HVAC controller? I can connect to all other modules using the VCDS though..

http://img6.imageshack.us/img6/2053/38zi.jpg (http://imageshack.us/photo/my-images/6/38zi.jpg/)

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Wraith600
10-23-2013, 06:19 PM
Not a 100 percent sure but I believe that I read somewhere that the auto hvac module is only for the newer models and not the b5 platform so you get comm errors when trying to communicate with that specific module. Check Ross tech's site on the specifics to that module.

As a side note I am having the same issue but am getting the core flushed this week because I can't be sure that's not my problem since I got the car used.

Why did you change those sensors?

If I keep my fan at about 2 or 3 bars its warm but as soon as I crank it up its like the core ant keep up with the air flow going over it and that turns it cooler. I would love my issue to be a sensor but I just can't see how that's possible.

woolveren
10-23-2013, 06:56 PM
As a side note I am having the same issue but am getting the core flushed this week because I can't be sure that's not my problem since I got the car used.

Why did you change those sensors?


I am still thinking whether a heater core can go bad in just seven months?? [confused] As I said, it was working perfectly alright early this year in spring..


I changed the IAT and ECT sensors because car was having some cold start issues; like it 2 or 3 more cranks for start.

woolveren
10-24-2013, 11:33 AM
So today I was looking at the outside air temperature and it's connection to see whether it's plugged in properly, but then I found this below.

Does anybody know what I am missing at 1 and 2? Also, which one is exactly the outside air temperature connector(in front of radiator)?

http://imageshack.us/a/img818/6977/8ytl.jpg (http://imageshack.us/photo/my-images/818/8ytl.jpg/)

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Toolaa
10-24-2013, 06:50 PM
Iíve recently flushed the antifreeze with genuine audi coolant and really donít think it's a clogged heater core

Today was the first winter like day in Baltimore. Similar problem. Only luke warm air after 30min driving and set on highest settings.

I changed my Turbo a few weeks ago and had to drain and recover the coolant. When I poured back my old coolant I had about 1/2 gal more than I took out. I opened the small bleeder valve above the fuel injectors and some air did vent so I was able to add about 4 more oz but not all coolant. So i have to believe there is some air trapped on the loop somewhere.

I read somewhere that the heater hose has some little hole on top and you remove the clip to slide back the hose which aligns the hole in the hose with a small hole on the heater core nipple. This is supposed to vent air trapped inside of the core.

However I looked at my hoses near the heater core and I couldn't see any hole.

Maybe we both have similar problems.

nynoah
10-24-2013, 06:54 PM
Basically lift up your coolant resevior really high and then run the car to temp. Use gloves and massage various hoses to get air out. I also use a mini funnel to pour coolant into the smaller hose that articulates into the top of the reservoir. In order to do that, you need to pull it off the reservoir. That helps with filling the system.

woolveren
10-24-2013, 07:19 PM
I think the heater core turned out to be a bitch in mine..

There is a good amount of temperature difference between heater inlet and outlet hoses when HVAC set to HI and on full blow..The heater inlet hose was pretty hot and not so easy to touch, but I can keep my finger on the outlet hose for longer times ..Sounds like a clogged heater core, right??? [headbang]

I still don't understand why this just happened in 6 months, the same core was blowing hot air in spring...

nynoah
10-24-2013, 07:47 PM
air in the core will also restrict flow and act like a block

Toolaa
10-25-2013, 03:29 AM
Ok I found the super massive thread explaining various methods of resolving heat problems

http://www.audizine.com/forum/showpost.php?p=5904838

Im going to look again for the small hole in the heater core pipe and see if i can get the air out.

Toolaa
10-26-2013, 08:26 PM
I think the heater core turned out to be a bitch in mine..

There is a good amount of temperature difference between heater inlet and outlet hoses when HVAC set to HI and on full blow..The heater inlet hose was pretty hot and not so easy to touch, but I can keep my finger on the outlet hose for longer times ..Sounds like a clogged heater core, right??? [headbang]

I still don't understand why this just happened in 6 months, the same core was blowing hot air in spring...

I have been messing around with this issue for the past two days. The inlet hose to the core is hot, the outlet hose is luke warm. When I pull the hose back a few drops of coolant come out at most. Rev Engine, Burp, Repeat...If the heater core was blocked then it wouldnt even get hot. I read the thread I linked from top to bottom along with half a dozen other threads about coolant and heater problems. I know there is air in the system. I've been burping and bleeding the frigging thing all day and I cannot get all the air out. My frigging knees are killing me from the akward bending to get to the bleeder hose and I'm getting coolant all over the place.

Tomorrow I'm going to go to Autozone and grab one of these things.

http://www.audizine.com/gallery/data/500/61hzJbLqqSL_SX425_.jpg

I am going to replace the outlet hose from the heater core to the oil cooler and insert the 3/4" tee right in front of the heater core nipple. Then I can easily attach a hose to the Tee and pour coolant right into the are that has the air bubble.

If this does not work then I'm ordering an Airlift 550000. Basically it's the same V.A.G. 1274 tool that the dealer would use.

http://www.audizine.com/gallery/data/500/VAS_6096_-_2.jpg

I'll let you know how things work out tomorrow.

ToXicXxX
10-26-2013, 09:42 PM
Or...

CLR + 3/4 hose on both ends of heater core. I did one flush, let it sit 45 minutes and BAM heat! Still works too, 2 weeks later. Rinsed the CLR out with copious amounts hot water after the fact.

Toolaa
10-27-2013, 01:53 PM
Looks like i'm making some progress. The Tee helped.

http://img.tapatalk.com/d/13/10/28/6ujysy7u.jpg
http://img.tapatalk.com/d/13/10/28/a8u9yhu6.jpg

I was able to top off to the highest point. I attached a small length of hose and massaged the different hoses. I could see air bubbling up and the level would drop slightly. Then I just added a little more water.

Now the heat from the vents is noticeably hotter. However it's also much warmer outside today. It still cools off at idle but not as much. We'll see tomorrow morning at startup when it's below 40 deg.


Or...

CLR + 3/4 hose on both ends of heater core. I did one flush, let it sit 45 minutes and BAM heat! Still works too, 2 weeks later. Rinsed the CLR out with copious amounts hot water after the fact.

I've never heard of CLR before but it looks like lots of peeps have used it before to clean coolant systems. The manufacturers instructions say it's not recommended for Aluminum surfaces. Do you run it through the engine or just the Heater Core?

woolveren
10-27-2013, 02:14 PM
I've never heard of CLR before but it looks like lots of peeps have used it before to clean coolant systems. The manufacturers instructions say it's not recommended for Aluminum surfaces. Do you run it through the engine or just the Heater Core?

I saw mixed reviews on CLR, some guys on other forums(not Audi) tells not to use in any automobile parts. This said, you REALLY don't want to run CLR through the engine. It may ruin your engine and other plastic parts. Just run it thru the heater inlet and outlet hose if you want to try it..

ToXicXxX
10-27-2013, 08:22 PM
I saw mixed reviews on CLR, some guys on other forums(not Audi) tells not to use in any automobile parts. This said, you REALLY don't want to run CLR through the engine. It may ruin your engine and other plastic parts. Just run it thru the heater inlet and outlet hose if you want to try it..

Just let it sit in the core, don't let it in your motor...

Wraith600
10-29-2013, 06:56 PM
Jus a quick follow up on my issue. Had it flushed today and upon picking the car up I was like 90 percent better. I only drove it for about 5 mins and as soon as the rad temp hit operating temps it was fantastic in comparison to what I had before. The true test is tomorrow morning when it's 3 degrees here.

I would make damn sure you use the proper coolant. (G12 if I recall). I used the genuine Audi coolant last time but I just wasn't confident that it was done properly. As well, I changed to a different brand as recommended from a euro tech, not sure if that mattered. My tech mentioned that he said the one hose leading to the back I the motor was better to flush from that the upper to a lot of how to's suggested. Honestly I haven't looked to see what he means. The key point was it provided a better flush point and wouldn't cause potential air / poor performance.

Hope that helps in some way.

woolveren
10-29-2013, 08:21 PM
Had it flushed today and upon picking the car up I was like 90 percent better. .

Coincidence or what, I had it flushed today as well and the heat is back.:) Upon driving the car for a while, I had to roll down windows as it was blowing pretty hot with 80F dial setting... In the past I had to keep it at 'HI' all the time with low fan speed to get some heat, Lol.

Anyway, I am glad that the heater is back to normal with a simple flushing. [drive]

Toolaa
11-02-2013, 12:05 PM
First chance I have had to work on the car all week. I use the Airlift to check for leaks and remove the air bubbles from my system. The thing works great. It's a bit messy trying to pre-fill the coolant suction hose. No big deal though.

Anyway, after evacuating the air my heat only slightly improved. Does anyone know for sure what temprature a working car should see comming from the vents?

I felt the hoses to the heater core and the lower hose was very hot and a bit uncomfortable to touch. The upper return hose is warm but not really hot still. I'm not sure if this is just normal as I would expect that as the hot coolant flows through the core it looses heat and cools down.

I scanned codes and got this:

00716 - Air recirculation Flap Positioning Motor (V113) 41-10 - Blocked or No Voltage - Intermittent

After searching it seems most other posters with the same error have a problem with weak AC but I didnt see any heat related issues when pulling that code. Does anyone know for sure if the Air recirculation flap would cause a reduction in heat comming from the vents?