hi.. i have a question my 93 300se w140 is not putting out any interior heat, i notice theres no water coming out one of the small hoses thats goes to the duno valve and back around on the passengers side all other hoses has water coming out good. could this be the vavle bad the hose on the firewall is steaming hot please help me i dont really have money to spare for a mechanic.

Try un-plugging the electrical connector from the heater (duo) valve & see if you get any heat.

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Already suggested that in a previous thread to him:
http://www.peachparts.com/shopforum/showthread.php?t=287087

He said "no change" so I would be tempted to say it almost has to be the duovalve, unless you have another suggestion. Of course I mentioned that the engine coolant has to be not low and the engine has to be warming up. Other than that I don't know what else it could be except a plugged heater core.

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