Jaguar XF Cooling System Causes AC Failure Alert

I dealt with a very similar issue on my 2013 Jaguar XJ diesel last year. I have some experience working with vehicle maintenance, but this particular problem required professional diagnosis. The symptoms were identical, AC not functioning and engine cooling system warnings. Initially thought it was a sensor malfunction, but diagnostic testing revealed a defective air conditioning control unit. The temperature sensor readings were incorrect because the control unit itself was malfunctioning. The repair involved: Complete diagnostic scan, Removal and replacement of AC control unit, Recalibration of the heat exchanger system, testing of all temperature sensors Total cost was 980€ for parts and labor. The workshop had to order the specific control unit which took about 3 days. Could you share: Current mileage on your XF? Are you getting any specific error codes? Does the AC fan run at all, even if not cooling? Have you noticed any changes in engine temperature readings? This info would help determine if your issue matches what I experienced and could save diagnostic time.

Thanks for the detailed response. My XF has 124073 KM on the clock, having just completed its annual service last month. The temperature gauge shows normal readings, but the AC fan runs intermittently. Getting error code P0128 which points to the cooling system. The temperature sensor seems to be sending inconsistent signals, making proper sensor calibration difficult according to my scan tool. Looking at the control unit you mentioned, any specific testing procedures you recall that helped isolate the issue from a faulty heat exchanger versus the control unit itself?

Thanks for those details about your XF. After dealing with my XJ issue, I learned some key diagnostic steps that might help. The P0128 code combined with intermittent fan operation definitely mirrors what I experienced. While the temperature gauge readings look normal, inconsistent sensor signals often indicate a deeper control unit problem rather than just a faulty heat exchanger sensor. The testing procedure that revealed the true issue on my XJ involved: Running the engine until fully warm, Monitoring live temperature sensor data through scan tool, checking voltage readings at the control unit connections, testing the cooling system pressure when cold and hot The inconsistent signals you mentioned are a classic symptom of a failing control unit. In my case, sensor calibration attempts failed because the control unit wasnt processing the inputs correctly, even though the sensors themselves were fine. The repair cost would likely be similar to what I paid (980€), but catching it early helps prevent damage to other cooling system components. Before replacing any parts, suggest having the workshop: Verify coolant level and quality, Test control unit ground connections, Check for any coolant leaks around the heat exchanger, Monitor sensor readings under various operating conditions The intermittent fan behavior combined with the P0128 code strongly suggests you have the same control unit issue I faced.

Thanks for the insights. After checking all the suggested points, I took my XF to a specialist workshop today. They confirmed exactly what was suspected, a failing control unit causing the intermittent cooling system behavior. The diagnostic testing showed identical symptoms to what was described. The sensor calibration attempts failed despite the sensors testing fine individually, pointing directly to the control unit as the culprit. No coolant leaks were found around the heat exchanger. Final repair cost came to 950€, which included: Control unit replacement, Full system diagnostic check, Recalibration of all cooling system components, Post-repair testing The AC is now working perfectly and all error codes have cleared. Really glad I caught this before it caused more extensive cooling system damage. The vehicle maintenance history helped speed up the diagnosis since they could rule out recent repairs or sensor malfunctions. Having the detailed testing steps helped me understand the repair process and confirm the workshop was on the right track. Appreciate all the technical guidance that helped solve this issue.