VW Transporter: Multiple Issues Linked to Temp Sensor

I had a similar situation with my 2008 VW Multivan, really close to your Transporter in terms of build and engine layout. I have some experience working on VW engines, mainly doing basic maintenance and troubleshooting. From what you describe, the issues point toward the AC control unit rather than the temperature sensor. The check engine light and error messages appeared on mine exactly the same way. Initially, I thought it was related to the engine cooling system or a faulty heat exchanger, but the workshop diagnosed a defective AC control unit. The fix required replacing the entire AC control unit module. The multiple error messages were happening because the unit communicates with several other systems. Total repair cost was 980€ including parts and labor. After replacement, all issues cleared up, no more check engine light, error messages disappeared, and AC worked perfectly again. To help further, could you share: Current mileage, Exact engine size, Whether the AC blower works at all, If the temperature gauge shows normal readings, Any coolant leaks or low coolant warnings This information would help confirm if your issue matches what I experienced with my van.

Thanks for sharing your experience. My mileage is 41804km and I just had the regular service last month. The AC blower indeed works, but no cold air comes out. The temperature readings look normal on the dash, and I havent noticed any coolant leak or warnings. What concerns me is that replacing the AC control unit seems quite expensive. Before going that route, did your workshop check for sensor malfunctions first? I read somewhere that sometimes these VW engine cooling sensors can trigger multiple error codes when they fail. Would it make sense to start with checking the sensors, since thats a cheaper fix? Really want to avoid unnecessary expensive repairs if possible.

Thanks for the additional details. In my case with the VW Multivan, the workshop actually did test the HVAC system sensors first, since they are cheaper to replace. They specifically checked the temperature sensor and several other sensor calibration points in the cooling system. What happened was interesting, the sensor readings were all within normal range when tested, but the AC control unit was misinterpreting these signals. A proper diagnostic showed the control unit was the core issue causing sensor malfunction errors despite the sensors working correctly. One thing to note though, your mileage is much lower than what mine had when the issue occurred (mine was at 158000km). This actually makes me think you might be right about checking the sensors first. The likelihood of a complete control unit failure at your mileage is lower. Ask your workshop to specifically test: Temperature sensor readings at various points, Pressure switches in the AC system, Communication between sensors and control unit The diagnostic test for these components usually costs around 80€, much cheaper than immediately replacing the control unit. If the sensors prove faulty, replacement costs typically range from 120€-200€.

I appreciate the detailed response and suggestions for testing. My mechanic is available next week, so I will definitely have them check all those sensor points first before considering the control unit replacement. The diagnostic test cost seems reasonable, and spending 80€ to potentially save hundreds makes total sense. What gives me hope is that you mentioned sensor calibration tests can detect these issues clearly. Since my van has such low mileage, starting with the engine cooling system sensors and working through the test points methodically seems like the right approach. If it turns out to be a simple temperature sensor issue causing all these error codes, that would be ideal. Will have the workshop do the full diagnostic testing of the cooling system and sensors first, then decide on next steps based on actual readings. Thanks for helping me avoid potentially unnecessary expensive repairs. Will update once I know what the actual problem is.