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The fan only starts after the engine is running, but it already feels significantly louder than normal. I never really noticed the fan before. After about 5 minutes, it goes to its highest speed.
This makes me think about air in the cooling system, though I don’t see how if the mechanic didn’t touch that. I would do a simple check to see if the low temperature on the radiator outlet (ECT2) is real. I would use either an IR thermometer, or maybe just carefully touch that pipe where the temp sensor is, or the sensor itself. I’m going to take a peek under my hood to see if it’s at all accessible…
Have you also the V8 or V6 Engine? Your are the best, thank you so much for your unbeliveable support so far... I think the V6 is different in this logic, and the ECT2 is also in a different position...
Thank you
Last edited by Andi Jaguar G; May 3, 2026 at 08:13 AM.
Ahh, that’s a good point. Both the Workshop Manual and Repair Manual I have are for the V6. Most stuff is the same, but not all. I have an early AJ133 training doc which doesn’t appear helpful, other than it only mentions the ECT sensor on the heater manifold on the back of the engine and not a 2nd ETC. https://www.dropbox.com/scl/fi/y28ug...=tse2tu3h&dl=0
Also, while the lack of codes isn’t helpful, it’s also troubleshooting information.
If the fan only goes to high speed after a few minutes, then that means the speed control signal (PWM) works, so I’m doubting JagCode’s suggestion of a pinched harness (though not impossible.) However, I agree with JC that’s it likely that the issue is related to the recent work.
I’m tending to think that the fan is operating as it should, something is making it run hard.
Also, the engine temperature display on the dash is garbage. Like most modern cars, once it reaches operating temperature, the display will stay exactly in the middle as long as the temp is within operating range (heavily damped). I’d suggest using your code reader to look at temperatures as the engine warms up.
I would include transmission temp too. I was looking at the transmission cooler, which uses engine coolant to cool the ATF fluid - and you just changed the ATF fluid. I was hoping to find a connection between the transmission temperature and fan control, but I did not see anything.
Ok, got it. Rear diff and transfer case were the only fluids changed this time.
Does anyone have documentation showing the location of ECT sensor 2? I have trouble believing it would be called an Engine Coolant Temperature (ECT) sensor if it was designed to measure ambient air temperature. (The V6 has 2 ECTs plus an Ambient Air Temperature (AAT) sensor.)
For those following along, my phone translated Andi’s pix…
Is this the answer?
The installation location is crucial: whilst the ECT1 sensor (primary sensor) is usually mounted directly on the engine block or cylinder head and measures the temperature directly
at the source, the ECT2 sensor (secondary sensor) is located at the radiator outlet or in the return hose on many modern vehicles.
The closed thermostat: As long as the engine is running warm and the thermostat is still closed, the coolant circulates only in the ‘small circuit’ within the engine.
The radiator remains ‘cold’, and the coolant at the ECT2 sensor moves little or not at all. The sensor therefore often displays only the ambient temperature or only a very slow rise.
The opening of the thermostat: As soon as the thermostat opens, the ‘large circuit’ is activated. Hot water from the engine now flows abruptly into the radiator. It is only at this
moment that the hot coolant reaches the ECT2 sensor, leading to a rapid rise in the measured values.
The ECT2 Sensor is in my view not defect or bad. Perhaps the thermostat or the relais is the problem when the cooling fan goes in a high run after 10 minutes
Thermostat: This component regulates the flow of coolant between the small and large cooling circuits to ensure the engine
operates at its optimum temperature. It is one of the most frequently replaced wear parts in the cooling system.
Relay: The Jaguar F-Type has a special radiator fan relay (often referred to as the radiator fan run-on relay),
which is located in the engine compartment. It controls the activation of the electric fans to prevent overheating.
Unfortunately, there has been no improvement; I get the feeling that the fan starts spinning up more aggressively after just a few minutes. I have an appointment with the Jaguar dealer on May 17th. I read out fault code U0001-87—though I had encountered this one previously as well. However, I suspect this is a result of the updated transmission software—at least, that’s how it seems to me. I can't say for certain, though.
So far, the Jaguar workshop hasn't been able to find a cause! No error codes were stored in the memory (no limp-home mode activated, no defective sensors; the thermostat also appears to be fine—no anomalies whatsoever), and everything else checks out. Yet, the fan still runs like crazy—spinning very hard—after just two minutes.
Therefore, if the control unit isn't sending a command for the fan to run at high speed, the only possible culprits in my view are the fan itself—specifically the small electronic module on the fan housing—or the fan motor. It’s very atypical, but what else could it possibly be? I honestly expected a Jaguar workshop to be able to offer more insight into this. After my initial phone call with them, I’m frankly a bit stumped. As I mentioned, the problem only surfaced after the rear differential and transfer case fluids were changed. However, that work was performed by a different workshop. One thing is certain: the fluids used are correct—all OEM fluids. Even if there were air trapped in the cooling system now, surely the Jaguar workshop would be able to detect that by analyzing the diagnostic data. I’m feeling a bit at a loss; I already possessed this level of knowledge before I even took the car to the Jaguar workshop. The air conditioning system was also cleaned, but that didn't turn out to be the cause either. Does anyone have any other ideas or suggestions I could pass along to the Jaguar workshop? Thanks a million, everyone!
i found this information over KI:
If the cooling fan on a Jaguar F-Type is running at full speed and no fault codes are stored in the engine control unit, the cause is usually a defective cooling fan control module or an implausible signal from the coolant temperature sensor. For quick and direct troubleshooting, it is recommended to utilize platforms such as the Jaguar Forums for vehicle-specific guides, or to use the official Jaguar dealer and workshop locator to have the problem professionally diagnosed. Since the "limp-home" mode is not active, the engine itself is usually operating within its normal temperature range. The following components are the most likely culprits: Fan Control Module (Fan Regulator): This is the most common source of failure. Often, the module (located directly on the fan housing) suffers from an internal defect, causing the fan to receive a signal for "continuous operation at maximum speed" without triggering a system fault code. Coolant Temperature Sensor: If the sensor supplies erroneous values—leading the control unit to believe the engine temperature is excessively high—the system activates the fan as a safety precaution. However, since the measured value remains plausible enough not to be flagged as an electronic fault in the diagnostic memory, the MIL (Malfunction Indicator Lamp) remains off. Air Conditioning Sensor (Refrigerant Pressure): If the A/C pressure sensor is defective or reports excessively high pressure, the cooling fan will also be permanently activated to cool the condenser. Broken Wires/Corrosion: Damaged wires or corroded contacts at the fan module connector can interrupt the control signal. The electronics often interpret this as a safety risk and run the fan at full power as a protective measure. Practical Quick Test: With the engine running, completely switch off the air conditioning system. If the fan nevertheless continues to run unabated at full speed, the fan control module is usually defective.
In my view, there is still the option to measure the voltage at the fan unit connector. Perhaps it isn't receiving the full 12 volts, causing the fan to spin at full speed. Alternatively, I could simply replace the entire fan unit—I might be able to get a used one here in Germany for very little money.
Didn't see this earlier, I will try to see what I can do to help. Was the engine raised/transmission lowered during the fluid change? You mentioned using a telescoping arm on the transmission, I assumed the support crossmember was moved and the trans lowered slightly to drain the oil? This could have pinched or damaged wiring if the engine was tilted too far.
ECT1 is on the rear heater manifold, ECT2 is down by the thermostat housing in the lower radiator hose area. Since your readings are off, I would inspect the wiring going to the sensors, and the values back at the PCM for the matching wires. If the shop you're using has OEM workshop manuals they should have no issue tracing that connection.
I would suggest checking the PWM signal to the fan. The engine fan gets power/ground, and then a PWM signal that determines how much it should run. You can watch the values in SDD datalogger and see what it should be, and also check at the fan, but if it starts low and goes high, that's showing that the PCM has control, it just doesn't know what to do and is cranking up the fan. If your thermostat was sticking and not allowing fresh coolant into the engine, the PCM could be commanding more airflow to help.
To be clear you do have a V8 right? Also if you could share your VIN, as the diagrams for the cars show two options, a standard RoW and a 'hot climate', one has a 500w fan and the other an 850w, just curious which one we are dealing with.
Cool, First thank you so much for your support and answer in this case, second sorry for my bad english!
Yes, its an V8 R AWD 5.0 Compressor and i think it is the 850 Watt Cooler, the Same as the SVR V8. My MY is 2017...
In my view is the big Questionen, why come this issue direct after the Fluid Switch, that cant be possible, perhaps yes, but i didnt believe it, better i can Not believe this.
First, WE will Check the pwm signal i think, a Problem with an broken wire is in my view possible...
Andi
Last edited by Andi Jaguar G; May 19, 2026 at 03:46 PM.
So if you lowered the transmission down, it raises the front of the engine. Can cause any sort of issues. I have seen on a Rover with a belt driven engine fan, the fan hit the shroud and caused other issues. Not the case here since it's an electrical fan, just to mention it.
I think you're on the right track with the engine coolant temp sensors, can you log the values of them, also the oil and air temps, from a cold start? Do they all match when cold, and does the coolant temp go up gradually in line with the other temps?
Added the workshop document for the cooling system. I could probably source it in your native language if that helps.
I would chase the circuit between the temp sensors and the PCM if that seems to be inconsistent. Voltage drop across the wires one at a time with the ignition on, should show up with any inaccuracies if the wires are damaged. Can also measure the actual values vs the reported values on the scanner.
Thank you ,this Information will help so much.
2 years ago, ZF flush the Gear Fluid and fill a new in it in my view this was the same work. Perhaps the transmission was already shifted too far out back then, and that original error was exacerbated during the subsequent work? It’s all speculation...
I have an Error Code since one or two years, but no problems with the cooling Fan in this time. Here the Code, sorry in german language.
