@NewShockerGuy

UPDATE:

2008 W211 E350 Base

Due to a "squeaking when car was going around corners" the OEM Blower Motor was replaced 2 years ago with a genuine BEHR Motor from FCP Euro.

The automatic HVAC system has worked flawlessly since the (NEW Behr Blower Motor & OLD OEM M-B Blower Motor Resistor).

A few months ago the blower motor was hesitating to activate, taking anywhere from 2 to 5 minutes after the car was started.

Once activated, the blower motor worked fine for the duration of the trip until the next key cycle.

So - 1 month ago, a Local M-B Specialist has since replaced the Blower Motor Resistor with one I sourced (Mahle/Behr brand Made in Germany) and topped off the Freon.

When the car drove out of the M-B Specialists garage, the A/C blower came on immediately, and the HVAC is as cold as ice.

A couple of days later, the electrical gremlin has re-appeared - that being the delay (sometimes) of the blower motor activation.

Here's how my father describes it (NOTE: he operates the HVAC by setting the automatic temperature control/cabin thermostat to 70 degrees and then leaves it alone):

• Sometimes when you start the car and the blower is not running. After about 2/3 minutes the blower starts and is OK for the rest of the trip.
• Or, after the blower goes on and runs for 5/6 minutes, it stops! If you leave all settings alone, it starts running again in a few minutes.
• Or, after the car starts, the blower comes on immediately and continues to operate normally throughout the trip.
• On our trip to Napa yesterday--Blower came on when the car started and operated normally to and back from Napa with a lunch stop in Napa.

OK - back to what I've since investigated:

I've read that there might be the possibility of an old FAULT CODE for the old blower resistor in the ECU that could be interfearing with the operation of the NEW Blower Motor Resistor.

Am I on the right track and should I get that checked ant the M-B Specialist?

Are there any other ideas of what could be the matter?

Please advise!

 

​​​​​Your blower motor + resistor are fine but at times they appear to have developed a mind of their own, right?

The blower fan speed is adjusted by the HVAC module to reach target heating/cooling temperatures.

The HVAC module is a sofisticated circuit that controls sensors and actuators. SCAN IT to see if yours complains about cabin temperature sensor....

Summer HVAC is super demanding on alternator power. Check that voltage remains good in the range of 13 to 14Volts. Ultimately add headlights and wipers... voltage should hold well.

 

Thanks to Forum Member Koingster for suggesting the following via Personal Message. Suggestion added for assistance to anybody else with this problem.
"You may also want to consider n22/7 diagnostics to rule out Control Unit": https://mbworld.org/forums/e-class-w...ml#post8515456

 

Just wanted to drop in and update this thread

Car was scanned with STAR software.

AN old HVAC code was present and removed.

After that operation was performed, my father said that the A/C operation improved somewhat, BUT, not completely.

A/C operation was good enough though that it made it through the very hot California Summer - a solid week of over 100 degree temps, reaching up into the 110's

I believe that the problem might be the actual "in-cabin" electronic thermostat / HVAC Module.

It's one of those things I'd like to work out BUT I don't know if they're going to hold onto the car or move on.

Thanks to all who tried to assist :-)

 

A couple of years ago I also had a squeaky blower, replaced it and everything worked well for a few months then the fan speed became erratic, not working at some higher speeds, replaced the original blower resistor as its called and all was well and still is. I think I have topped off the R134A (3) times, never a shop, since 2006 due to lack of cooling performance.

it would be helpful for you to pry from your father the exact symptoms the blower is having now. Or test it yourself.

 

Since I posed in this thready from earlier.

I went through and bought a used HVAC panel a week or so ago. This was because I had already replaced my blower motor twice witha new OEM unit, and also changed out the blower motor regulator, twice and OEM new units. I kept getting an error in STAR stating the blower motor regulator was at fault. It was annoying because I couldn't understand how that could be via replacing it twice?

So, I swapped over the new to me used HVAC panel. Part numbers aligned making sure it was the same one that was in my 09'. Plugged everything in and then ran through STAR to reset everything and adapt the new unit to the car. Turned the fan speeds up down..etc. All worked. YAY. This was much better than what was happening with my stock unit where I had to have it on fan setting 2, and have the air in all 3 directions. If I moved the air positioning elsewhere it would stop. Then I could be driving, and it would kick back on again. If I pushed the Auto button it would eventually come on and at full blast, then I could turn the fan speed down to 2-3 and it would work.
However, when I pushed the AC button it would just blink on this new unit I got. Wouldn't turn on the AC compressor. I thought that was odd since my older unit had no issues with the AC and it got cold...etc.
Thinking my system was then low I slowly filled it up with the r134a I had. (I have a set of AC gauges). Something still wasn't clicking with me. So I took the used HVAC panel back out, put mine back in and didn't program it and pushed the AC button. Stayed on and AC was nice and cold.

Made no sense... so I reprogrammed my stock HVAC unit tot he car again and then went through all the tests and adaptations. Thus far all fan settings/positions are working. I am not getting any codes in STAR and I guess I was going through a bad run of blower motor regulators... seems odd. The ONLY thing I can think of is perhaps that ebay guy I bought them from was selling defective OEM units... cause the box and everything was new.

So as of right now everything is functioning how it should. It's nice having to adjust the air when needed rather than keeping it on all the time and at position 2 fan speed...lol

I ordered one from RockAuto and just checked it was 6 months ago. Surprisingly I clicked on my order to see if they could warranty it. And to my surprise they ARE! I send it back to them and they will issue me a full refund! Totally awesome! So at least that's another piece of good news...w00t w00t!

-Nigel

 

Seems like the problem is back again with an erratic fan speed either working or not working. This is truly frustrating. As soon as I hit the fan mode I get a quick spirt of air then it shuts off. I can put it in auto and after a minute I can feel air ramp up like it's trying to do something then it turns off and stays off. I can push a bunch of buttons and then randomly it might stay on or might not. If I turned the dials to hot air then it start blowing air and if I turn it all the way down it seems to stay but if I start out low it won't turn on. I could try another HVAC control panel but all the message I'm getting on star points to the blower regulator which has been replaced with new OEM 3 times now... I'm tempted to buy a used motor and regulator here on the forum just to test something completely different. Seems llike also if I don't drive the car for a couple weeks this happens. Where once I replaced the blower motor regulator and drove the car every day it was fine. Not sure why that would even matter.

Love MB but it almost seems like this is overly complicated way of handling air management..lol

I can hook it up to STAR and it runs through the HVAC tests and it all goes as planned. Air blowing out full speed/half speed...etc. all being adjusted and can see the regulator adjusting voltage, no problem. I unhook STAR/computer and we are back to it working/not working off and on. It's really odd. No other errors codes other than it senses the regulator being the problem.

-Nigel

 

Still having this annoying intermittent issue...lol.

Replaced everything still showing no codes. All wires intact. I can start the car with the air on and it immediately starts, other times I can hear a puff of air starting then it just stops. Then it tries again and stops. I drove up to PA a couple weeks and it took 35 minutes before the air started to finally turn on, and then it stayed on the entire 4-5 hour trip.

I have noticed if I have it on position 4 for the fan it tends to stay on, as soon as I lower it to 3 or below then it will kick off eventually. All random times, nothing is consistent at all in terms of how it's handling air. It really does seem like a silly complicated way of how it handles the air... I have a 17 year old Solara that it just works every time, adjust the air zero issues. This thing just makes no sense.

I feel like if I took the car in to a dealer not only are they going to charge something crazy, they'll come back and say "blower motor relay" is the problem. Replace it, it will work for a week then go back to the behavior that keeps happening now. I've replaced the blower motor, relay and hvac all with OEM parts and it still sometimes just works out of the gate, and then other times takes 20+ minutes for the air to finally come on. This is true at any temp.

I almost feel like if the car gets driven more this is less of an issue compared to driving it not as often...etc.

Who knows. German cars are nice but man stuff like this is extremely frustrating. I want a Porsche at one point in my life but with how integrated and overcomplicated things are, it seems numbing to own any car outside of the warranty... And I consider the w211 one of the last "good" ones to actually own.

-Nigel

 

You saved me a ton of diagnosing effort. I installed a new Mahle Behr blower and resistor/regulator in my 2003 W211 E500 August 2024. It failed in March 2025. While searching for other potential part failures that might cause the same symptoms, I ran into this thread. Thank you for following up to share that it was indeed your blower. I just replaced the blower with another identical one from FCP Euro (lifetime replacement) and it now works again!