Mondeo mk4 fan not turning, preventing AC working
Discussion
Hi all,
New mk4 mondeo 2.3 petrol estate owner here (“Ooooo rare model!”). Please can you help me?
The car’s aircon was not great when we bought it, so I had it regassed. Since then, it works great when driving at speed (as low as 8 degrees, confirmed by a temperature probe in the vents.
However, the AC does not work when in traffic or parked.
The cause appears to be a fault causing the radiator fan not to turn, which is preventing the AC working at low or nil speed. You press AC and the fan ignores you (but AC compressor does turn). What’s weird is the radiator fan clearly has nothing physically wrong and briefly turns soon after the car starts.
What I have tried so far to diagnose cause:
Assuming the first regas was somehow done wrong, confirmed with two separate garages the amount of refrigerant in the car is right and there appear to be no leaks.
Changed the AC pressure sensor between regas 2 and 3 with a brand new pattern part.
Mechanic scanned the car with a Autel MS908, found a ‘Fan 1 control circuit’ code recorded. He cleared it, instructed the fan to turn and it did. Then the AC began blowing very cold, then the fan stopped. He rescanned and the code has reappeared.
Mechanic confirmed that two engine temperature sensors appeared to work, with both reporting the same data to his scan tool.
Changed fan control unit for an identical genuine one from a breaker. Went back to mechanic to reset code. Reappeared.
Inspected purple control wire from fan control unit, all the way to about 1 inch from the PCM/ECU. This included The 2 tight turns the wire makes, which I read online are a common place you will find damage to the wire. The wire looks like new all along this length, not even a hint of damage.
Removed glove box, changed pollen filter. Reseated all connectors I could find under there (hoping one is the evaporator sensor one forum post mentioned as a possible cause).
I should mention too that my speedo works, so I assume the car knows when it is stationary/slow. The coolant temperature on the dash also works - indicated as cold when first starting, turns to the middle in a few minutes and never goes past this (even in really hot weather or traffic). I have also directly connected the battery to the fan and is spins nice and fast with no nasty noises.
I am considering the following next steps, feel free to suggest alternatives:
A. Assume both the original and used control unit I brought have an issue, so replace with new.
B. Assume the fan motor is somehow triggering the issue, perhaps causing voltage spikes? Replace with new.
C. Assume the PCM/ECU has a fault. Have a Ford dealer carry out diagnosis.
I’m really sick of this now and would be very grateful for any advice. Even just some moral support would be nice!
New mk4 mondeo 2.3 petrol estate owner here (“Ooooo rare model!”). Please can you help me?
The car’s aircon was not great when we bought it, so I had it regassed. Since then, it works great when driving at speed (as low as 8 degrees, confirmed by a temperature probe in the vents.
However, the AC does not work when in traffic or parked.
The cause appears to be a fault causing the radiator fan not to turn, which is preventing the AC working at low or nil speed. You press AC and the fan ignores you (but AC compressor does turn). What’s weird is the radiator fan clearly has nothing physically wrong and briefly turns soon after the car starts.
What I have tried so far to diagnose cause:
Assuming the first regas was somehow done wrong, confirmed with two separate garages the amount of refrigerant in the car is right and there appear to be no leaks.
Changed the AC pressure sensor between regas 2 and 3 with a brand new pattern part.
Mechanic scanned the car with a Autel MS908, found a ‘Fan 1 control circuit’ code recorded. He cleared it, instructed the fan to turn and it did. Then the AC began blowing very cold, then the fan stopped. He rescanned and the code has reappeared.
Mechanic confirmed that two engine temperature sensors appeared to work, with both reporting the same data to his scan tool.
Changed fan control unit for an identical genuine one from a breaker. Went back to mechanic to reset code. Reappeared.
Inspected purple control wire from fan control unit, all the way to about 1 inch from the PCM/ECU. This included The 2 tight turns the wire makes, which I read online are a common place you will find damage to the wire. The wire looks like new all along this length, not even a hint of damage.
Removed glove box, changed pollen filter. Reseated all connectors I could find under there (hoping one is the evaporator sensor one forum post mentioned as a possible cause).
I should mention too that my speedo works, so I assume the car knows when it is stationary/slow. The coolant temperature on the dash also works - indicated as cold when first starting, turns to the middle in a few minutes and never goes past this (even in really hot weather or traffic). I have also directly connected the battery to the fan and is spins nice and fast with no nasty noises.
I am considering the following next steps, feel free to suggest alternatives:
A. Assume both the original and used control unit I brought have an issue, so replace with new.
B. Assume the fan motor is somehow triggering the issue, perhaps causing voltage spikes? Replace with new.
C. Assume the PCM/ECU has a fault. Have a Ford dealer carry out diagnosis.
I’m really sick of this now and would be very grateful for any advice. Even just some moral support would be nice!
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