Mercedes-Benz Forum banner

1 - 15 of 15 Posts

·
Registered
Joined
·
204 Posts
Discussion Starter #1 (Edited)
When the car starts, climate control always defaults to off, regardless of what it was on before the car was turned off. Is there a way to make it stay on whatever it is set at? That's not normal is it? First world problem but it's annoying to have to turn it on every time and the only car I've driven that doesn't just do what it was doing last time. No codes being thrown, weird thing is about a year ago I had the reverse problem, it always came on high, but I think that was before I replaced the old blower with an s-class one and cleaned out the hood vents that were gunked up.
 

·
Registered
Joined
·
5,446 Posts
It should not do that. Mine starts blowing with the key in position 2, with set temps on the screen.

When the engine starts, it will start the compressor and start cooling or heating.
 

·
Registered
Joined
·
204 Posts
Discussion Starter #3
That's what I was thinking, wonder why it's doing that. Just got the compressor replaced so it's running pretty well.
 

·
Registered
Joined
·
5,446 Posts
Maybe you have blown a fuse in the process. Check fuses 4 and 7 under the hood at the driver's side.

The controller remembers the settings when you remove the key. The controller is still powered by fuse 4.

Try pressing and holding the REST key with the key removed for 30 seconds. Check if the controller comes alive and the blower fan starts.
 

·
Registered
Joined
·
204 Posts
Discussion Starter #7
MrBoca + Witek_M
Checked all the engine compartment fuses and they all looked good. The REST function doesn't do anything and never has as far as I can remember.
tabijan
When you turn it on, it always starts on OFF, no matter how you left it.

Would it help to pull out the control unit and unplug-replug the connectors? Thanks all, if you have any ideas let me know.
 

·
Registered
Joined
·
891 Posts
I mean when you turn on ACC, e.g., press the Auto button, with the engine just started, does it go back to how you left it?

Sixto
98 E320 wagon
02 C320 wagon
 

·
Registered
Joined
·
5,446 Posts
MrBoca + Witek_M
Checked all the engine compartment fuses and they all looked good. The REST function doesn't do anything and never has as far as I can remember.
tabijan
When you turn it on, it always starts on OFF, no matter how you left it.

Would it help to pull out the control unit and unplug-replug the connectors? Thanks all, if you have any ideas let me know.
Just to clarify, when you turn the key to position 2 (not yet starting the car), do you see the temperature settings on the display, then the blower starts,

or

nothing shows, no blower?

If the display shows the temp settings and then you start the car, only then the display goes blank ?
 

·
Registered
Joined
·
204 Posts
Discussion Starter #10 (Edited)
tabijan When you press the auto button after turning the car on, it defaults to 72 both sides which is where I usually leave it, I also usually leave the charcoal filter on and that comes on too. I'll check to see if it will come on at a different temp too.Edit: I checked and I guess it always goes to 72 no matter what.
mrboca When car is off the screen is blank, and when you go to key position 2 the OFF appears on both sides of the screen and stays that way even when you turn the ignition all the way, and I don't think the blower or anything happens until you manually turn it on. Maybe there is some debris or something and it's trying to make sure no more gets in so it closes everything off? I've been getting kind of a whistle at higher fan speeds so maybe I need to go in and clean something out? Edit: I checked out the cabin filters and they look fine and are only a couple months old, the carbon filter is too but I didn't check it.
 

·
Registered
Joined
·
5,446 Posts
OK. There is a difference between OFF - OFF display and display is turned OFF :)

I still feel that the controller is not getting "Always ON" power. You checked the fuses 4 and 7 and you say they look OK, but you need to check the voltage on them (they have little tabs on them one tab at each side, that you could make a measurement between each tab and the chassis ground nearby. Sometimes the fuses are fine but the fuseholders are either loose of suffer from corrosion. Fuse 4 should have power all the time, while fuse 7 has the power when the key is turned.

The best way is to test if the power actually comes to the controller connector. Fuse 4 goes to pin 8 of connector 2 at the controller which is of red/blue color.

OFF is OFF. No blower will turn on. I do not think the controller is clever enough to detect debris. Normally when you turn the key to position 2 the temp settings you made will be displayed and the blower will turn on to whatever the setting was. When you turn the key to start the car, the ignition will tell the controller to stop during cranking to provide maximum power to the starter. After the car starts, you get the blower running again. (controlled by circuit 15x).
 

·
Registered
Joined
·
204 Posts
Discussion Starter #12
Thanks, I don't have the electrical expertise but will ask my mechanic to take a look next time I see him, maybe this is why the rest feature has never seemed to work that I recall.
 

·
Registered
Joined
·
5,446 Posts
Right. For the REST to work, the controller has to have power when the key is out. If the REST button works (if it allows you to go to the sensor menus, then it does work), and the unit is powered, when you press the REST the unit display should come alive.
 

·
Registered
Joined
·
204 Posts
Discussion Starter #14
This is probably a dumb question but could a wire just not be a little loose, would it worth pulling out the ac unit and unplugging/plugging things and blowing it out with compressed air? That's about the outer limits of my electrical understandings.
 

·
Registered
Joined
·
5,446 Posts
Nothing wrong with visual inspection.

Check the red/blue wire that goes to pin 8 of connector 2 (of two connectors).

Electrically, you can check it the red / blue wire gets 12V with respect to ground (pin 19 in the same connector which is colored brown), if you have a multimeter and know how to use it.
 
1 - 15 of 15 Posts
About this Discussion
14 Replies
4 Participants
mrboca
Mercedes-Benz Forum
BenzWorld.org forum is one of the largest Mercedes-Benz owner websites offering the most comprehensive collection of Mercedes-Benz information anywhere in the world. The site includes MB Forums, News, Galleries, Publications, Classifieds, Events and much more!
Full Forum Listing
Top