Well if you removed the power to it and it went to full heat sounds like it's working, so it's probably the interior temp sensor either not working or the asperator motor is not pulling air across the sensor.
Sent from my iPhone > On Dec 23, 2016, at 5:58 PM, Curley McLain via Mercedes > <mercedes@okiebenz.com> wrote: > > 124 300D (87) > > Driver complains heat is sometimes working and sometimes not. I have avoided > this diagnosis before by paying someone to do it. That guy is NLA (Kicked > the bucket) I unplugged the monovalve, and it appears it is delivering full > heat. > > What is the diagnosis to figure out if the monovalve needs a new insert? > > Coolant tank was a little low, but not dry. It only took a quart or so to > fill it up. I am 95% sure the problem is not lack of coolant flow through > the heater. > > I am guessing either PBU or monovalve, and leaning toward the latter. > > How do you test the circulation pump? get heat going, then unplug the circ > pump and see if amount of btus goes down? > > I still prefer the simple 2 valve and a fan switch for heater control. VERY > reliable, few failure modes. > > > _______________________________________ > http://www.okiebenz.com > > To search list archives http://www.okiebenz.com/archive/ > > To Unsubscribe or change delivery options go to: > http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com > _______________________________________ http://www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
