JHS666

Hi, I have a 2015 E220. The issue im having is with the interior heating.
If the car was at full operating temperature etc. and I was driving it, if i had the interior temperature set to 27 degrees and i switched it down to 26 degrees, the air starts blowing cold (luke warm) air. Or if i had it set to 26 degrees and turned it down to 25 degrees it goes cold. I have to set it to 26 degrees or above for the air to be warm, anything under thats is cold.

The cars engine temperature is correct and coolant level is correct. I have also carried out diagnostics on the vehicles HVAC and shows no fault codes. The live data readings seems ok. All the sensors are working.

Did anyone else have this problem with the w212 model?

Any help appreciated.

Mud

I wonder if there is an issue with the heater valve? Its in the engine compartment and controls coolant flow through the heater core. I've seen online posts before about them failing or partially failing. Result is no heat or low/ lukewarm heat. I don't think its an expensive or difficult part to replace.
Just taking a shot at it, but might give you something to look into.

dbldpr

If it is still under warranty bring it into dealer. or you can call service dept at dealership and ask if that is normal.

KEY08

If it was the heater control valve as Mud suggested, you would have received a fault code if it was not opening or closing properly. It is controlled by the front S.A.M. and that may be faulty as well. Once again, though it would throw out a fault code. Not sure what your problem may be, but the operation is not normal. I guess you need to get it into the dealer for more specific tests.

JHS666

Thanks for your replies.
Ok so i would have a fault code for the heater valve unit if it was faulty? As that was where i was thinking of going next with it but i have no fault codes.
Yes i think I have to get a main dealer look at it however i was talking to to 2 different main dealers and they never came across this problem with a w212 having these sort of issues and theres no bulletins issued about this problem. So i didnt want to just leave it into a main dealer and them checking exactly what ive checked and not having an inclination of what is wrong. I have also emailed Auto Data as we have a subscription service with them and they normally have alot of fault bulletins about vehicles and had nothing about this issue i stated.

I just thought maybe someone had this problem previously with the w212, but thanks for your help.

Mud

I understand what Key08 says about the fault codes but what I'm thinking is possibility that the valve receives operational commands but yet does not operate correctly. SAM thinks it has sent the command but I'm not sure that the valve itself is set to throw a code if it's defective. Sort of like a defective thermostat in a car - it doesn't throw a code on its own until other temp or operational sensors detect an issue.
Again I'm just guessing and could well be wrong. It would be interesting to hear how this issue was finally resolved, I guarantee someone else will encounter it at some point.

Oda112

This has been discussed here before and it turned out it was a matter of personal preference when it came to describing the behavior of the automatic climate control system. My question is: are you feeling cold in the car altogether? Let's say the outside temp is 20F or -5C and you request 27C in your car. Does it blow colder air(or none at all) through the center vents and warmer through the footwell ?If the answer is yes, then that's the normal behavior for this car. It will almost never blow warm air through the center vent regardless of the outside air temperature ( we were driving in -8 C weather two weeks ago, had the inside temp set at 24 C and I never felt any warm air blowing through the center vents, only through the side ones and footwell, but overall we were comfortable wearing our t-shirts in the car) . The only time I've felt warm air through the center vents was when I set the temp to HI ( 86/88 F, 32C) . Also, I've noticed that when the outside temp goes up by one or more degrees, the climate control will blow colder air through the center vents for a few seconds, and the other way around for when it gets colder.
Bottom line, if you're not overall cold in your car, everything is working fine, you don't need to throw money at it.

JHS666

Hi, no i have checked this and it is blowing cold air from the windscreen vent and footwell, its not just the center vent like you were saying which i would understand.

Oda112

That's no good. I would have it checked, there are quite a few things that could be wrong and without a proper diagnostic tool it would be difficult to figure it out.

JHS666

Ive carried out diagnostic checks as i mentioned about and nothing from the live data seems out of place and also no fault codes. Im more going in the line that its the heater valve unit that is at fault which i think im going to try first. I just wanted to see did anyone else have this issue as ive asked 2 dealers also about this problem in this model and both said they havent come across it so there only going to be guessing like myself. Thanks for your replies tho. I will update post when i try and get it sorted.

Oda112

The infamous heater valve was a well known issue on the previous model and the W221 chassis as well, I wasn't aware it's present on the W212 too. Regardless, that should be easy to diagnose. If you have access to a diagnostic unit, you can follow the air inlet temps(outside air) and the different cabin outlet port sensors after your engine is up to operating temperature. I played with mine last week and if I remember correctly there are sensors in the drivers footwell, side and center vents (the same goes for the passenger side) which show live data. There might be one in the heat exchanger core too but I'm not sure. If all your outlets blow cold air that would suggest a bad heater valve, if not, it could be a bad blend door somewhere. Those can be tested individually and recalibrated. I'll play with mine later and see what numbers I get.

JHS666

If you would have the time to check that, i would appreciate it, to compare it to mine!

Oda112

Outside temp was 29F and climate control was set to 74F for both driver and passenger. Doors and windows closed, engine temp 96C. I don't know what's up with the 8000 value for the "current flap position", it's been like that since I can remember it, it doesn't seem to affect the actual output temps. It might be a tester fluke, unrelated to actual live values.



Main menu for AC live data


Actuator motor menu


M16/22


M2/16


M2/5


M2/6



M2/7


Sun intensity sensor


Evaporator temp


All air outlet temps

Darel

Holy crap. What diagnostic tool is giving you that sort of readout? I need one of those!

Oda112

It'a an Autel MaxiDAS DS808, I got it on sale on amazon 2 wees ago. I was considering getting one of those chinese STAR contraptions, but didn't like the price, warranty and overall difficulty of use so I decided to take a chance on one of these and I must say I'm very impressed. As far as I know, it does everything the STAR does minus SCN coding, which the STAR system won't do either unless you have a subscription( they have a more expensive version called Autel Maxisys Elite which will do that too). I've played with it a few times and it can do adaptations and active tests for pretty much everything that needs it ( including TCM, ECU, Headlights, Night Vision camera, Distronic, etc.) and it's not limited to MB. I tried it on my Ford truck and it can even code new ignition keys in( it gets past the PATS system, it's a 10 min procedure, made me feel like I was in a car movie hijacking scene but with added nerdiness).
On my W212 it changed the setting in the climate control system to make it show the blower speed even in auto mode, but there are numerous more settings there. I impressed the wife by remotely opening and closing the trunk lid with it ( and consequently escaped all the possible purchase price related nagging).
I've also diagnosed a 2015 Toyota Sienna and a 2014 BMW X3 and again, I was impressed, it's very powerful, gets updates almost daily and it works with all car manufacturers that I've heard of. On the BMW, which was a 2.0 diseasel it even had a DPF regen function, amonghts other goodies.
I can do an in dept review if there's interest for it here.

Darel

Thanks for the info. I felt a little guilty paying $200 for my Innova unit (which I've never actually tried plugging into the MB yet), so this is a little pricey, but nice to know it's out there for all the advanced functions. Still way, way cheaper than a STAR or a Snap-On unit.

Oda112

I looked at getting a cheaper, semi-pro obd2 scanner, but most of them aren't proven to work with all the modules on the W212 ( mine has 46) and they definitely do not perform all the fancy functions this one does. Price-wise, I think it's a good investment, it will pay for itself after 6-8 scans (considering stealership prices for diagnostics) and after that you're just making money and might even not have to buy your own beer ever again if you decide to help your friends and scan their cars (at least that's what I'm hoping for ).

belarus27

For real , this scanner is great went on ebay to check out a price , and its around 450 and up.
i wish u were from Sac lol

Oda112

I'm definitely bringing it with me whenever I travel long distance in the future. If I'm ever headed your way I'll be more than happy to let you try it.

JHS666

Thanks for that information. I compared the live data readings to mine for the temperatures etc. and they all seem to be reading near the exact same with the similar conditions, however i cannot read position values etc. as my scanner does not show me as much as yours. Thanks for taking the time to do this for me! My problem still insists so i will just have to leave it to the dealer to figure out.

JHS666

Hi,
Can anyone shed any light on this yet?
Im still having the same issue👎

GSN212

Hello,
I'm curious on if you were able to get this issue resolved as I am having a similar (if not the same) issue. My mechanic told me I need a software update at the dealer as everything else seems to be working fine. Was this the same issue the dealer diagnosed on your car?

Any advice is appreciated.