No heat
MBWorld Fanatic!
Joined: Jan 2014
Posts: 3,973
Likes: 1,320
From: Republic of Texas
'99 and '05 E55 AMG
Sure it can be bypassed but then you get max heat all the time.
Remove wiper blades.
Dismount yaw sensor and move to one side.
Remove plastic cowling.
Remove wiper mechanism.
Remove heater control valve.
Install short hose from coolant supply line to one of the heater core connections.
Install another short hose from other heater core connection to the coolant return line using a brass nipple.
Reinstall wiper mechanism
Reinstall cowling.
Reinstall yaw sensor.
Reinstall wiper blades
After the above, you still need to figure out what is up with the heater control valve...and perform the work all over again.
If the heater control valve is OEM dealer purchased, where I am at there is a 2-year warranty on parts. If not a parts issue, you need to look at the HVAC system.
Remove wiper blades.
Dismount yaw sensor and move to one side.
Remove plastic cowling.
Remove wiper mechanism.
Remove heater control valve.
Install short hose from coolant supply line to one of the heater core connections.
Install another short hose from other heater core connection to the coolant return line using a brass nipple.
Reinstall wiper mechanism
Reinstall cowling.
Reinstall yaw sensor.
Reinstall wiper blades
After the above, you still need to figure out what is up with the heater control valve...and perform the work all over again.
If the heater control valve is OEM dealer purchased, where I am at there is a 2-year warranty on parts. If not a parts issue, you need to look at the HVAC system.
Last edited by bbirdwell; Dec 30, 2025 at 09:54 PM.
