Smart Fortwo Heater Valve Fix: Common Issue Revealed

I had a very similar issue with my 2009 Smart Forfour last winter. With some basic car repair experience, I initially tried checking the coolant levels and inspecting visible connections, but the heating remained weak. The workshop diagnosed a faulty cable connection at the water valve that controls coolant flow to the heater core. The valve itself was working, but the electrical connection had deteriorated over time, causing intermittent operation. This explained why the heating performance was inconsistent. The repair involved replacing the wiring harness section and properly securing the connection to the automotive valve. Total cost was 95€ including diagnostics. Since the fix, the heating system has worked perfectly with no coolant leaks or valve blockage issues. Before suggesting specific solutions, could you share: Current coolant level status, Whether the heating is completely non-functional or just weak, If the problem is constant or varies with engine temperature, Any unusual sounds when adjusting the temperature controls This information would help determine if your issue matches what I experienced or might be something different in the heater system.

I wanted to provide an update on my heating issue. After checking the cooling system thoroughly, I found low coolant levels which partially explained the weak heating performance. However, even after a proper coolant refill, the car heating remained inconsistent. The diagnostic error codes pointed toward a valve blockage affecting coolant flow to the heater core. Interestingly, my last service was at 155000 KM and the heating was working fine then. I checked for coolant leaks around visible hoses but found no obvious issues. The irregular heating behavior and error codes make me think a valve replacement might be needed, but Id appreciate more specific diagnostic steps before proceeding with repairs.

Thanks for the update on your Smart heating issue. When my car showed similar symptoms, topping up the coolant also provided only temporary improvement. The inconsistent heating you describe matches exactly what I experienced before finding the real problem. In my case, the diagnostic steps that helped identify the issue included: Checking coolant temperature with the engine running, Testing if heat output changed with different engine RPMs, Listening for the water valve operation when adjusting temperature controls The main sign that confirmed my valve problem was the heating would sometimes work normally for a few minutes before becoming weak again. This irregular pattern is typical for failing water valve components in the cooling system. Based on your mileage and symptoms, I recommend having the valve assembly inspected. My repair became necessary around 160000 KM, close to where your car is now. The car heating inconsistency despite proper coolant levels strongly suggests either a valve blockage or electrical control issue. Consider requesting a specific valve operation test during diagnostics. This helped identify my issue without unnecessary parts replacement. The complete diagnostic process cost 45€ before the actual repair was started.

Thanks for the input. After reading through the responses and checking all the suggested points, I did some additional troubleshooting. The cooling system was properly filled, but I noticed the heating performance definitely varies with engine RPM, which seems to point toward the automotive valve issue mentioned. I scheduled an appointment to have the heater core and valve assembly checked professionally. The intermittent nature of the problem and the error codes make me think replacing the valve might be the solution, but I want to confirm there are no electrical connection issues first. Given the mileage on my Smart and the typical failure patterns described, this seems like a logical step. Will update once I get the proper diagnosis and repair completed. Its helpful to know others have resolved similar car heating problems without major system replacements. The diagnostic cost mentioned seems reasonable, so I feel more confident about proceeding with the professional inspection.