Ok with the temp outside almost reaching 100 sometimes i GOTTA turn on the AC. my car dash will read 84-94 lets say. + degrees.

i run the AC juuuust fine. then all of a sudden lets say 45 mins later my temp on the dash starts going crazy!!!!!!!! it will read -56 degrees and the AC wont turn on b/c .. it thinks its toooo cold!

whats going on!?

98 A4 1.8t.

also, is anyone in the NYC area able to lend me a hand to fix the sun roof. this sucks! i have a couple of bucks, but not enough to pay a damn stealership.

 

I am having exactly the same issue with my 2001 A4 avant - it was 90+ degrees this weekend and the temperature guage was bouncing back and forth between -40 and +60, blowing hot air most of the time.

The dealer just replaced the thermostat two months ago, and now of course they can't find anything wrong. Help!

 

yeah i had the same problem but it only happened when it rained so the only defrost it had was hot. didnt do anything and it hasnt done it lately. if you find out what it was pm me

 

Dealer has now been able to replicate the problem, and is replacing the interior temp sensor. I am dubious but hopeful that this is the answer...

 

There are two sensors total,
1, the exterior temp sensor which is located behind the bumper which tells you the outside temp.
2, the interior temp sensor which is located inside the a/c control head
If the exterior temp sensor can turn off the a/c if it reaches below 32 degrees, so if that sensor malfunctions replace that and check the resistance of the wires.
If the interior sensor malfunctions, the interior temp will fluxuate. For instance if you set the temp to 70 degrees and its 100 inside the car it should turn on the a/c when in the auto function, when it malfunctions it might not turn on the a/c or even the heater.

 

so.. replace the bumper temp sensor?? if the temp on my Car Dar is reading -40 when outside its 100 degrees lol. ok. ill try this.

 

My dealer replaced the exterior sensor about a month ago, so theoretically it works. He's saying the interior one is the issue now. Not sure how they communicate to the AC controller.

 

im not into A/C but I do know it has to be set up at 22c for the system to work correctly VAG or read the manual

 

Basic setting[/align] Basic setting[/align] Preconditions: �Coding checked and corrected if necessary => Page01-69. �Fault memory interrogated => Page 01-67. �Engine still idling after the interrogation of the fault memory �Air conditioner switched on ("auto" mode). [/ul] → Indicated on display Rapid data transferHELP Select function XX[/align] ‒Enter "04" for the function "Starting basic setting". [/ul] → Indicated on display Rapid data transferQ 04 - Starting basic setting[/align] ‒Confirm entry with Q key. [/ul] → Indicated on display Initiate basic setting Q Enter display group number XXX[/align] ‒Enter "001" for "display group number 001" and confirm entry with Q key. [/ul] The following positioning motors are actuated consecutively and their end positions stored in the operating and display unit -E87 (resistances of potentiometers installed in the positioning motors). ◆Temperature flap positioning motor -V68 ◆Central flap positioning motor -V70 ◆Footwell/defroster flap positioning motor -V85: ◆Air-flow flap positioning motor -V71 [/ul] Note: Up to Model Year 1996, the installation of the positioning motor -V71 was dependent upon equipment and it is therefore not installed in all vehicles (e.g. not in right-hand drive vehicles). → Display readout: Basic setting 1⇒ XXXXXXXXXXXX[/align] It is possible to track the movement of the positioning motors on the display (feedback values change). → Display readout: Basic setting 1⇒ 0000[/align] When the display zones show 0, the basic setting is finished. ‒Press ⇒key. [/ul] → Indicated on display Rapid data transferHELP Select function XX[/align] ‒Interrogate fault memory => Page 01-15. ‒When the last fault has been displayed and printed out, rectify the faults according to the fault table => Page 01-18. [/ul] Notes for vehicles up to Model Year 1996: ◆The positioning motor -V71 or the refrigerant temperature sensor -G110 depend upon the equipment and are therefore not installed in all vehicles. During the basic setting, equipment-related absence is stored as a fault.
-Refrigerant temperature sensor -G110 "Open-circuit /short to positive /SP".
-Potentiometer -G113 in positioning motor-V71 "Open-circuit/short to positive /SP". ‒Check whether these components are installed in the vehicle. ‒If they are not installed, when the last fault has been displayed and printed out, press the ⇒ key. ‒Erase the fault memory => Page 01-67. [/ul][/ul] ◆The interrogation and erasure of the fault memory immediately after the basic setting cause an equipment-related absence of the positioning motor -V71 and/or the refrigerant temperature sensor -G110 to be stored and no longer displayed until the initiation of the next basic setting. [/ul]

 

Turns out there was a loose wire which was getting caught in the fan and intermittently shorting out the system. Dealer only discovered this while attempting to replace the interior temp sensor. Everything now working fine.