logo elektroda
logo elektroda
X
logo elektroda
Advanced Search
logo elektroda

Audi A4 B7 1.9 TDI: AC Stops Cooling at Standstill After Compressor & System Repairs

henryxxl 10422 11
ADVERTISEMENT
Treść została przetłumaczona polish » english Zobacz oryginalną wersję tematu
Report a violation of the law
Reply | New topic
  • #1 16622335
    henryxxl
    Level 26  
    Posts: 1402
    Help: 32
    Rate: 103
    Hello.
    My car is audi a4 b7 1.9 tdi. Last year I bought this car and at the beginning I added a factor to the service and unfortunately I found it unlucky to have it so bad that it has seized a compressor that worked earlier. I chose another better service and replaced the compressor, air conditioning coolers plus cleaning the entire system from filings (yet another service replaced the compressor without cleaning it and the other one has faded). I replaced the compressor twice, the overall costs increased to a large sum but now everything is fine. The air conditioning is cooling for the second year but the problem appeared in the heat which now passes through our country, so the air conditioning turns off at a standstill, while driving it cools as it should.
    The air conditioning fan is spinning but it turns out to be too inefficient. The service that fixed my air conditioning firmly stated that the fan controller was to blame. My question is whether it is for sure because I do not want to put extra costs in air conditioning which has cost me a lot anyway. I borrowed a cable with a laptop from a friend who possesses vcds. I did read the errors:
    Code: C / C++
    Log in, to see the code

    I received such a mistake, deleted it and after two weeks it has not returned yet but the air conditioning at the stand still works badly.
    Yesterday I did read the data that the computer requires a fan speed of 86% and the actual read speed is 78% and did not rise above this value. I am asking my colleagues to show me what readings to make to see if there is a damaged fan, fan controller or maybe something else because I do not want to invest money in the dark where I can not see what is damaged.
    The repair is private (own car) not for commercial purposes.
    Regards ;)
  • ADVERTISEMENT
  • #2 16622779
    barteksmrek
    Level 28  
    Posts: 1309
    Help: 89
    Rate: 222
    The reason may be too low power of the alternator at low revolutions in relation to the demand of the air conditioner which in such heat works at high parameters. Stop at a standstill and hold the car for 1500-2000 turns and see if it turns off. The reason can also be insufficient cooling of the air-conditioning radiator at a standstill as it is when driving.
  • ADVERTISEMENT
  • #3 16622808
    henryxxl
    Level 26  
    Posts: 1402
    Help: 32
    Rate: 103
    I forgot to add in the previous post that engine speed does not affect the operation of air conditioning. I suppose this is something with cooling but exchange the blind driver I see on average.
    Regards :)
  • #4 16622848
    Strumien swiadomosci swia
    Level 43  
    Posts: 27411
    Help: 1403
    Rate: 6379
    Pour the condenser over with water and see if the efficiency increases.
  • #5 16623856
    henryxxl
    Level 26  
    Posts: 1402
    Help: 32
    Rate: 103
    I checked at low speed how the car rolled and cooled. My question is as to the speed declared and the actual fan. As well as this error which I attached earlier.
  • ADVERTISEMENT
  • #6 16623954
    T5
    Admin of Cars group  
    Posts: 12856
    Help: 1004
    Rate: 4158
    What do the system pressures look like?
  • #7 16623970
    henryxxl
    Level 26  
    Posts: 1402
    Help: 32
    Rate: 103
    Gentlemen from the repairing company rated the pressure too high when stationary as it is very hot outside.
    If you need any data from the vcds program, please write with great pleasure to solve my problem :)
  • #8 16623983
    T5
    Admin of Cars group  
    Posts: 12856
    Help: 1004
    Rate: 4158
    henryxxl wrote:
    Gentlemen from the repairing company rated the pressure too high when stationary as it is very hot outside.

    And there is already a lead.
    Now what do the coolers look like, especially the space between them?
    Aren't they covered with crap, dust, straw, leaves?
    As there is ok, unfortunately the fan to be repaired and replaced.
  • ADVERTISEMENT
  • #9 16623992
    henryxxl
    Level 26  
    Posts: 1402
    Help: 32
    Rate: 103
    The radiator was replaced with a new one for repair because from what I know it cannot be 100% cleaned and the compressor would seize again. The problem is that these mechanics have found that the fault is the controller and not the fan and I would like to know what exactly. The fan controller is located next to the fans.

    PS.
    Are these fans repairing?
  • #10 16624000
    Strumien swiadomosci swia
    Level 43  
    Posts: 27411
    Help: 1403
    Rate: 6379
    henryxxl wrote:
    The problem is that these mechanics have found that the fault is the controller and not the fan and I would like to know what exactly

    And for what, you don't fix it.
  • #11 16624005
    T5
    Admin of Cars group  
    Posts: 12856
    Help: 1004
    Rate: 4158
    It's about the space between the coolers.
    The fan can be checked from the tester level.
  • #12 16624019
    henryxxl
    Level 26  
    Posts: 1402
    Help: 32
    Rate: 103
    Tomorrow I will check this space between me, it seems original. As far as the test is concerned, I did it and spins like in normal work, unless there is another test.
    As for the matter that I should not care because I do not fix it, I will say that they do it for my money and if they are to exchange in turn, I thank you for such repair. Air conditioning made by them was a year ago and then there was this problem but I forgot about it because the days were colder and this year the sun is starting to warm up again and I want to fix it myself.
    I am interested in the short circuit error of the fan, I have to get to it maybe something is rubbing against the winding.
Reply | New topic
Report a violation of the law

Topic summary

✨ The discussion revolves around an Audi A4 B7 1.9 TDI experiencing air conditioning (AC) issues, specifically that the AC stops cooling when the vehicle is at a standstill, despite functioning properly while driving. The owner previously replaced the compressor and cooling system components due to a seized compressor. Responses suggest potential causes including low alternator power at idle, insufficient cooling of the AC radiator, and issues with the fan controller. Suggestions include checking system pressures, cleaning debris from the coolers, and testing the fan's operation. The owner is particularly interested in the fan controller's role and whether the fan itself can be repaired.
Generated by the language model.

FAQ

TL;DR: VCDS showed 86% fan request but only 78% actual, and a P1945 short-circuit code; “computer requires a fan speed of 86%.” [Elektroda, henryxxl, post #16622335]

Why it matters: If your Audi A4 B7 1.9 TDI AC cools while driving but not at idle, this FAQ helps DIY owners quickly isolate fan, controller, or condenser issues to avoid repeat compressor failures.

Quick Facts

Why does my Audi A4 B7 AC stop cooling at idle but works while driving?

Lack of condenser airflow at standstill raises high-side pressure, which reduces cooling and can trigger shutdown. While driving, ram air lowers pressure and restores cooling. Debris trapped between radiators or a weak fan/controller often causes this exact pattern. Inspect the condenser face and the space between heat exchangers for blockage. If the area is clear, test the fan via scan tool and verify commanded vs actual speed. Elevated stationary pressures are a key clue. [Elektroda, T5, post #16623983]

What does DTC P1945 (006469) mean on this platform?

P1945 (006469) indicates “Control Module 1 for Cooling Fan – Output Short Circuit – Intermittent.” It points to the fan control path, wiring, or integrated fan electronics. Clear the code, perform an output test, and compare requested versus actual fan speed. If the fault returns during heat soak or idle, focus on the fan module and harness near the shroud for chafing or water ingress. Note the freeze-frame for temperature and duty cycle context. [Elektroda, henryxxl, post #16622335]

How can I quickly confirm if airflow is the problem?

Do a safe water-spray test. With the engine idling and AC on, gently pour water over the condenser. If vent temps drop or compressor behavior stabilizes, the condenser lacked airflow. That implicates the fan, controller, shroud seals, or blocked fins. This is a fast A/B diagnostic that isolates heat-rejection limits without gauges. Dry electrical components afterward and avoid soaking connectors. [Elektroda, Strumien swiadomosci swia, post #16622848]

How do I test the radiator/condenser fan using VCDS?

Use Output Tests in the engine or HVAC module to command the fan. Observe whether the fan ramps smoothly through stages and matches requested percentage. “The fan can be checked from the tester level.” If the fan fails to reach targets or stalls, suspect the fan module or wiring. Record requested vs actual RPM or duty cycle for comparison with live data on the road. [Elektroda, T5, post #16624005]

What live-data numbers suggest a weak fan or control issue?

If the control requests high speed (e.g., 86%) but actual stalls lower (e.g., 78%), the fan is not achieving target airflow. Combine this with high stationary pressures or rising vent temps to confirm. A repeated intermittent short code strengthens the case for a control-side fault. Capture data at idle after heat soak to reproduce the condition. [Elektroda, henryxxl, post #16622335]

Could low alternator output at idle be the cause?

Low alternator output at idle can limit fan and clutch capacity during heat waves. Briefly raise engine speed to 1,500–2,000 rpm at a standstill and watch if cooling stabilizes. If RPM has no effect, focus back on airflow and the fan circuit. This check helps separate electrical supply limits from mechanical airflow problems. [Elektroda, barteksmrek, post #16622779]

What should I inspect between the coolers?

Check the narrow gap between the AC condenser and the engine coolant radiator. Remove packed dust, leaves, straw, or road debris that block airflow. Even with a newer radiator, trapped debris can accumulate and choke the condenser at idle. If this area is clean and symptoms persist, prioritize fan repair or replacement. [Elektroda, T5, post #16623983]

Is replacing the condenser necessary after compressor failure?

After a seized compressor, cleaning or replacing the condenser helps remove metal filings that can destroy a new compressor. Many shops replace the condenser because it’s difficult to flush completely. This reduces recurrence risk and stabilizes system performance over time. Verify the condenser is truly new and fins are unobstructed to protect the replacement compressor. [Elektroda, henryxxl, post #16623992]

How do I interpret the freeze‑frame data from VCDS?

Use RPM, vehicle speed, voltage, coolant temperature, and duty cycle to set context. Example: at 882 rpm idle, 14.14 V system voltage, 90°C coolant, and 9.7% duty you can assess electrical headroom and fan command. Track Fault Frequency (e.g., 11) to understand intermittency. Correlate with ambient heat and standstill conditions. [Elektroda, henryxxl, post #16622335]

Can I repair the fan or just the controller, or must I replace the unit?

The B7 often integrates control electronics with the fan assembly. Intermittent short faults and failure to reach commanded speed typically justify replacing the fan module. Inspect harnesses and connectors first. If output tests pass yet cooling is weak, recheck debris and shroud seals before parts replacement. [Elektroda, T5, post #16624005]

What’s a simple 3‑step way to isolate the fault path?

  1. Perform a fan Output Test with VCDS and log requested vs actual response.
  2. Water‑spray the condenser at idle; note any cooling improvement.
  3. Inspect the gap between condenser and radiator; clear debris and re‑test. [Elektroda, T5, post #16624005]

What’s an edge case I should not overlook?

A clean condenser face can still hide debris wedged between the condenser and radiator. This chokes airflow only at idle, mimicking a weak fan. Always separate and inspect that gap before condemning electronics. If the gap is clean and pressures remain high, address the fan assembly. [Elektroda, T5, post #16623983]

Does raising engine speed help diagnose alternator vs airflow issues?

Yes. Hold 1,500–2,000 rpm at a standstill and watch AC performance. If cooling returns, alternator output at idle may be marginal. If nothing changes, airflow or fan control remains the primary suspect. This quick differentiation avoids unnecessary parts swapping. [Elektroda, barteksmrek, post #16622779]

What quote best sums up the diagnostic approach here?

“The fan can be checked from the tester level.” Use scan‑tool output tests before buying parts. It validates the control path and fan response. If results are inconsistent, recheck wiring and consider replacing the integrated fan module. [Elektroda, T5, post #16624005]
Generated by the language model.
ADVERTISEMENT