Smart Fortwo A/C Failure: Compressor Diagnosis Guide

As someone with moderate experience working on Smart cars, I dealt with a very similar issue on my 2011 Smart Forfour diesel last summer. Initially thought it was the AC compressor too, but it turned out to be an undervoltage problem affecting the AC relay switch. The symptoms were identical, no cooling, AC not engaging at all. The workshop found that the voltage supply to the AC relay was insufficient, which prevented the system from activating properly. They had to replace the AC relay and check the entire charging system. Total repair cost was 240€ including diagnostics. Before jumping to conclusions about the compressor, have these checked: AC relay switch condition, Pressure switch functionality, Battery voltage under load, Refrigerant leak presence, All related fuses Could you share: When did the problem start? Does the AC fan blow at all? Are you getting any specific error codes? Have you noticed any electrical issues with other systems? This information would help narrow down if youre dealing with the same underlying voltage issue I experienced.

Thanks for sharing those details about the relay switch. The AC problem began suddenly last week. The AC fan does blow but no cold air comes through. Car has been regularly serviced, last maintenance was at 148000km. Getting error codes P0531 and P0534. The battery and charging system were actually replaced during the last service, so I doubt its an electrical issue. Havent noticed any problems with other systems. The belt tensioner was also replaced recently, so the compressor belt is properly tight. Starting to think the A/C compressor itself might need replacement since all other components seem to be working fine. Will get the refrigerant level checked too before making any decisions. Would an A/C compressor replacement be worth it on a car with 151262km, or should I consider other options?

Great follow-up on your AC troubles. Since we had similar problems with our Smart cars, I think I can offer some relevant insights. Based on those error codes (P0531 and P0534) and the symptoms you describe, this does point more toward an A/C system pressure issue rather than the relay problem I experienced. With a properly working belt tensioner and new electrical system, the compressor is becoming a more likely suspect. In my case, after fixing the relay issue, I actually ended up replacing the compressor about 20000km later when similar symptoms developed. The repair was around 850€ including labor and refrigerant recharge. Given your mileage (151262km), a compressor replacement could still be worthwhile if: The rest of the A/C system is in good condition, You plan to keep the car for at least another 2 years, You regularly need air conditioning Before committing to a compressor replacement, make sure to: Check refrigerant pressure levels, Test the pressure switch operation, Verify no major leaks exist The investment made sense in my case since the car ran reliably for several more years after the repair. Just ensure you get a quality compressor and have it installed by someone familiar with Smart AC systems.

Thank you for the detailed information about the compressor replacement cost and timeframes. Those error codes and symptoms do seem to point toward a pressure-related issue, which makes sense given the HVAC system history. I will first have the pressure sensor and pressure switch tested since these are less expensive components to replace. The workshop can also check refrigerant levels and look for any leaks while they have the system open. If those all check out fine, then I may proceed with the compressor replacement since I plan to keep the car for at least 3 more years. The 850€ cost seems reasonable considering it includes labor and recharge. My local workshop quoted similar prices when I called them earlier. Since the rest of the AC system components are in good shape and I use the air conditioning regularly, investing in a new compressor makes sense despite the high mileage. Will update once I get a proper diagnosis and decide on the repair path. Thanks again for sharing your repair experience, it helped provide perspective on what to expect cost and longevity-wise with these AC system repairs.