A/C warm and cold

**lanman1** · 08-02-2008 08:47 PM

Please help.......I have a 2003 A4 1.8T cabriolet and the a/c coming from the vent to the left of the steering wheel is cold, the A/C coming out of the windshield defroster vent is cold but the air coming out of the right hand and center vents varies from lukewarm to a little cold. I have tried running the temps all the way to hi and back down to low and the air blows hot then cools again. You think maybe one of the blendor motors isn't closing the mixer all the way? Is there a way to access the ducts and flappers without tearing the whole dash apart? Anyone with a manual have any sort of a layout diagram of the duct system?

TIA

**brewmastr** · 08-02-2008 09:17 PM

all the stepper motors for the heater box are easily accesible by removing the glove box, there is a stepper motor for left and right side, right side is identified by a violet linkage and the left side is identified by a red linkage, this is copied from my resources i have here it is some crap about the linkages.

NOTE: This positioning motor moves two flaps, these flaps are connected in the air conditioner via a coupling rod (not visible from outside). In the event of a temperature control complaint, the connection between the flaps can be checked with the heater core removed but without removing the air conditioner (for visual inspection check flap through the opening). Reach through hole of heater core into air conditioner and move flaps via the external actuator lever.

in all honestly that sounds like a pita, i would try replacing the right side temp blend motor and see what you get.

**lanman1** · 08-03-2008 05:20 AM

Thank you very much for the info. I'm going to start tearing it apart right now.

**diagnosticator** · 08-03-2008 06:03 AM

Originally Posted by lanman1

Thank you very much for the info. I'm going to start tearing it apart right now.

With a VAG-COM, and a Bentley, there is extensive diagnostics and functional output tests available, as well as relevent trouble codes. Can you have the A/C controller scanned for DTCs?

**lanman1** · 08-03-2008 07:23 AM

Originally Posted by diagnosticator

With a VAG-COM, and a Bentley, there is extensive diagnostics and functional output tests available, as well as relevent trouble codes. Can you have the A/C controller scanned for DTCs?

I do have a VAG cable and bought the full version of the software. What would I look for?

I just took it apart and put it back together. It doesn't appear to be blendor or motor related. The motors go through their full travel and the linkages seem solid. When I manually move the linkages they do seem to close the flappers as far as I can tell. I am hoping that it is just low on freon or that it's the orifice tube and that since it isn't cooling as well as it should, some vents are just warmer than others???????

Thanks again for all the help/advice

**diagnosticator** · 08-03-2008 11:48 AM

The first thing is to scan the A/C controller for Fault Codes. Save any stored codes, and clear the existing codes. Drive the car and rescan to see what codes are again stored. In Basic Settings, after accessing the A/C controller, in Measureing Block 001, will reset the air flap servo motor feedback values stored in the controller.

Scan for codes, and post back what you find, and we can go from there. If there is a large temp difference between vents, it's not an issue with the refrigerant, if that was the case, the air temp would be to warm overall, not just from some of the vents. But, there may be a seperate need for a recharge, it's not the cause of the large difference in vent air discharge temp however.

**lanman1** · 08-03-2008 06:09 PM

Originally Posted by diagnosticator

The first thing is to scan the A/C controller for Fault Codes. Save any stored codes, and clear the existing codes. Drive the car and rescan to see what codes are again stored. In Basic Settings, after accessing the A/C controller, in Measureing Block 001, will reset the air flap servo motor feedback values stored in the controller.

Scan for codes, and post back what you find, and we can go from there. If there is a large temp difference between vents, it's not an issue with the refrigerant, if that was the case, the air temp would be to warm overall, not just from some of the vents. But, there may be a seperate need for a recharge, it's not the cause of the large difference in vent air discharge temp however.

Thanks for the help. I did t read all the way through your instructions before I started so I screwed up. There were some fault codes the 1st time in but I cleared them without saving, sorry. This may have been caused by my tinkering earlier today unplugging the servos and temp sensors. I did the meas block 001 and it went through the recalibrate procedure. I drove it 15 minutes or so and still no codes.

I did a little more troubleshooting not that it has cooled off this evening and found this.
If I turn the fan down really low, all the vents get cold. When I turn the fan up above 1/2 way or so, the middle and right vents start to warm a little and the left vent stays cold. Coul this just be low freon or the orifice tube and the left vent's airflow is coming across a cooler part of the A/C core?

**lookaught** · 08-05-2008 11:03 AM

Before my car's AC system was recharged the drivers side vent near the door was significantly colder than the rest. Once it was recharged, they all blow very similar cold air. The pre-recharge temp difference was quite large, it would be uncomfortable on the passenger side of the car b/c no vents blew cool air, while the drivers side was pretty comfortable b/c of that one vent.

So it could be that you are just low on refridgerant... have you checked that?

EDIT: I fixed mine with a $25 recharge kit that has a gauge about a month ago. Works perfectly now. It is apparently important to vacuum bleed the system first per diagnosticator, but I didnt do this and my AC works really well. Its up to you, at least its a cheap first attempt before you take your car into a specialist. I kick myself for not doing it sooner, I drove all last summer and half of this summer with really really shitty AC, and a recharge fixed it in 10 minutes in a parking lot.

**lanman1** · 08-05-2008 03:25 PM

You were 100% correct. I took it to the shop and they evacuated the system, put in compressor oil, added dye, and refilled. Now all the vents are cold. The only thing I can figure is the leftmost vent and the defroster vent are closest to the coldest part of the core.

Thanks again for everyone's help and advice.

**strider-g3** · 06-29-2012 10:54 PM

same problem with my 04 3.0L. only left vent is giving coldest air. regardless of outside air or A/C air. cold air only blows out of one vent. hope the refill thing works for me too!

**gsommerp** · 08-01-2012 12:51 PM

Strider-g3

did the refill fix yours? I have the same issue, cold on left, warm center right, and warm right.

**shane_yank** · 11-25-2012 12:27 AM

Originally Posted by gsommerp

Strider-g3

did the refill fix yours? I have the same issue, cold on left, warm center right, and warm right.

gsommerp, I'm flipping this back on you :)

Did you every get a recharge? If so, did it work? This past summer I had the most uncomfortable drive to/from Tahoe!

**gsommerp** · 12-23-2012 10:31 PM

I still have not done anything with mine. Now I notice in the winter, the heat seems to have the same issue. The car never really heats up like it used to. Do you have that issue, now that it is winter. I am about to take mine in next week to a tech. Sorry for the late response, I have not been on here for a while.