I own a 1987 190E 16v and the heater does not work at all. I searched for monovalve on the site, but I don't think the valve described in the threads is the valve used on my car. My valve doesn't have an electrical connection. It has a vaccuum which connects to the top of a black bulb. The vaccuum is what opens and closes the valve. The part that confuses me is that the valve is constantly open, so I should constantly be getting heat. This is not the case. I get forced air through the vents, but it is only outside air. Brrrrrrr. I checked the coolant and it is topped up. I am not sure if it is the control unit in the dash because when I push the buttons, the vents that the air is pushed through changes. I also have no air conditioning, does this have anything to do with the heat? Could the heater core need replacing? Could a citric acid flush possibly clean out any contaminants in the heater that are blocking the coolant? I would appreciate any suggestions. I don't really want to go through another winter without heat.