Still no Heat after Changing Changeover Valve
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Joined: Mar 2020
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From: Louisiana
2009 W211 E350 and 2011 S212 E350 long-roof
Still no Heat after Changing Changeover Valve
Hello, I (mis)diagnosed a failed changeover valve when my 2009 W211 E350 stopped blowing heat a few days ago. I always operate the climate system in Auto and 72 degrees in summer and winter and it has worked well for the 11 months I've owned the car. However, the system now only blows cold air. Initially the situation resolved itself after a few hours but the problem returned the following day and remained. After a deep forum/YouTube/internet search I concluded it must be the changeover valve so I replaced it today using p/n A 211 832 05 84, which was the same p/n already installed.
I topped up the coolant reservoir IAW owners manual direction and still no heat even after the car came up to its 85C operating temp. I didn’t find any leaks from the new valve after the change and noted that the hose on the engine side was warm but the top hose on the valve itself was not. I presume that’s the return hose?
In the cabin I changed the climate control settings from Auto to various manual programs with both heat temps at their max, selected Max Defrost, changed to various blower speed settings all with no improvement.
I’m presuming an electrical issue now but haven’t been able to find any further on-line details because it seems everyone who posted how to change the valve had success and heat. I’ll take any suggestions you experts may have.
I topped up the coolant reservoir IAW owners manual direction and still no heat even after the car came up to its 85C operating temp. I didn’t find any leaks from the new valve after the change and noted that the hose on the engine side was warm but the top hose on the valve itself was not. I presume that’s the return hose?
In the cabin I changed the climate control settings from Auto to various manual programs with both heat temps at their max, selected Max Defrost, changed to various blower speed settings all with no improvement.
I’m presuming an electrical issue now but haven’t been able to find any further on-line details because it seems everyone who posted how to change the valve had success and heat. I’ll take any suggestions you experts may have.
Last edited by Jim Stratton; Feb 11, 2021 at 06:51 PM. Reason: Remove Icon
Thread Starter
Newbie
Joined: Mar 2020
Posts: 14
Likes: 0
From: Louisiana
2009 W211 E350 and 2011 S212 E350 long-roof
Thanks Aeon, I think the reservoir is good because I haven't seen fluid under the car (the washer fluid IS leaking however which is a separate subject)
After the car sat overnight, I drove it today and the climate control system worked normally in Auto and Max Defrost with the temperature of the blown air changing to warm when I selected full hot and back to normal when I returned them to 72deg. Fingers crossed the issue is resolved, but if not I'll update the post. I read on the other forum about the HCV 'frying' the control chip on the front SAM with the solution being to purchase an inexpensive new chip and having a trusted computer repair tech remove the old chip (heating instead of cutting the solder seems to be the right answer) and soldering the new chip on. The challenge is disconnecting the SAM board from the car, but other than that the procedure seems straight forward and has resulted in successful fixes. That said, chasing electric gremlins can be a huge exercise in frustration so I'm hoping my system simply maybe had some air in it and that the new HCV is now working correctly.
After the car sat overnight, I drove it today and the climate control system worked normally in Auto and Max Defrost with the temperature of the blown air changing to warm when I selected full hot and back to normal when I returned them to 72deg. Fingers crossed the issue is resolved, but if not I'll update the post. I read on the other forum about the HCV 'frying' the control chip on the front SAM with the solution being to purchase an inexpensive new chip and having a trusted computer repair tech remove the old chip (heating instead of cutting the solder seems to be the right answer) and soldering the new chip on. The challenge is disconnecting the SAM board from the car, but other than that the procedure seems straight forward and has resulted in successful fixes. That said, chasing electric gremlins can be a huge exercise in frustration so I'm hoping my system simply maybe had some air in it and that the new HCV is now working correctly.
