My heater is blowing cold air only
Thread Starter
Newbie
Joined: Jan 2013
Posts: 7
Likes: 0
From: Michigan
S550 & S500
My heater is blowing cold air only
For some reason, my heater only blows cold air after the car has warmed up and even after driving for 15 minutes, it still blow's cold air.
Sometimes it works and most of the time it only blows cold air.
can anyone tell me where to begin?
Thanks
Steven
Sometimes it works and most of the time it only blows cold air.
can anyone tell me where to begin?
Thanks
Steven
Member
Joined: Oct 2008
Posts: 179
Likes: 2
From: Chicago, Naperville area
2005 Mercedes S600, 2004 Mercedes E500 4-Matic, 2002 Mercedes C32 AMG, 2001 Trans-Am WS-6
Depending on the exact symptoms, it could be a number of things...Perhaps a stuck/dead duo valve ( ~$275 for the part - diverts hot coolant to warm up the vents), or bad thermostat (inexpensive) or water pump, or bad push button control panel ($300-400 for the part), or bad flapper mix stepper motor ($45 part but requires 8-10 hours removing the entire dashboard depending on which one it is, or a temp sensor somewhere (inexpensive).
(I'd suggest looking it up in the sticky up top for common W220 encyclopedia, it's in there under HVAC).
If it's warm when you're stopped, and cools off when you drive faster but the temperature gague reads normal, I'm guessing the duo valve (happened to me).
If your temp gague flucutates w/ speed, or the air warms up with high revs and cools off at lower rpm, try the thermostat or waterpump.
If you hear clicks or buzzing from behind the vents, it's the stepper motors.
(I'd suggest looking it up in the sticky up top for common W220 encyclopedia, it's in there under HVAC).
If it's warm when you're stopped, and cools off when you drive faster but the temperature gague reads normal, I'm guessing the duo valve (happened to me).
If your temp gague flucutates w/ speed, or the air warms up with high revs and cools off at lower rpm, try the thermostat or waterpump.
If you hear clicks or buzzing from behind the vents, it's the stepper motors.
Last edited by marktan; Jan 11, 2013 at 12:04 PM.
Super Member
Joined: Feb 2009
Posts: 780
Likes: 11
From: Dallas, TX
Range Rover
Might be a quick fix , try this, drive the car and get it warmed, then, raise the temp to 80 degrees or heat or just raise it high and the have both passenger and driver vents manually aimed to blow air only to the bottom. Last set your fan speed manually and see if you feel heat at least going to the floor. No , it's not fixed but at least you will be able to heat your car.
