mushu405

So my car's heat and air does not kick in on low speeds it seems. Driving around in the inner streets I won't get past 50 MPH or so and the heat does not kick in. BUT every morning when I am driving to work about 5 minutes in and going 70 MPH it will all the sudden kick in.

At first I thought oh the blower must be out but once it kicked in then thats theory is out the window.

Has anyone else heard of this issue?

Background on my car. 2007 S550 with 86k miles on it.

DaveW68

Possibly a cold weather issue? It's frickin freezing here in Chicago....and the heat won't kick on until the engine is warm. While waiting for that to happen, I just enjoy the heated seats and steering wheel which heat up quickly.

mushu405

I was thinking that....BUT driving around the "lower" speeds and the engine fully heated up it still doesnt kick in.

I was thinking maybe relay switch or temp sensor is not working properly?

Nuru

Sounds like the system is either configured incorrectly or there is a sensor issue. The heat should show up once the engine is warm. Does this occur on automatic setting or does it occur on the manual setting, or both?

triniexr

I still can't figure out what the 3 settings do lol.. Diffuse, focus, and the other one which I can't remember right now.

Nickthegreek

Sounds like your blower motor is going. They start seizing up from moisture. I just replaced my blower motor because I had a similar issue. The defogger would not turn on until I was driving it for a while at high speed. All of a sudden it would turn on. Then if I went to turn it on again the same problem, until it finally just crapped out on me. Costed $260 dollars for the part at the dealer. Common problem. Not complicated, but its kind of a pain in the *** because its in a confined spot. Now I hear a vortex of wind once I start it up

mushu405

Where is it located exactly? Being in a confined spot was it still simple to replace?

mushu405

Sorry I didnt see this. Both manual and auto settings.

Nickthegreek

It sits right under the passenger side glove comparment. There's a panel under it you take out, then you pull the carpet back and fold it to make room to remove the panel. Then the blower motor is a white unit sitting right under the glove compartment. There are 3 t30 I believe torx screws holding the panel. Then you have to get 5 t30 screws on the blower. It's really confined so it's kind of a pita. Then once you get the screws it will dangle on the power cord. You flip it so you can see the fans and there will be a regulator you have to unscrew it with a t30 again and then coerce it out and unplug 2 plugs. Then install it into the new blower and install the blower. Just be careful not to lose the screws while loosening/tightening them. Took me about a half hour

Nickthegreek

Nickthegreek

mushu405

So just an update on this. Nick thank you for your suggestion! It was the blower that went out! Replaced it and now it works again for more cold weather in Oklahoma lol.

Thanks everyone who helped on this thread.

Nickthegreek

Anytime! Glad I could help. It's very annoying. I found out in the expresway when my windows fogged up on me and couldn't see a dam thing!

mbzphil

I too had a similar problem last year (no heat at all). The dealer replaced the blower and everything was fine for until this winter season . Now the only way to have heat is to go off auto, adjust fan speed to 6 or 7%, and manually set the diffuser to be mostly at feet and some through the vents. Occasionally everything resets to 78 degrees and auto. I re-adjust and everything works in manual mode again. The weird part is AC works on auto with no issues.

Any thoughts on what to check?

Nickthegreek

Wonder if mayne the module that controls the air duct plenums might need to be reset with star?

mbzphil

I will research that. I was too thinking software as it resets to 78 degrees and fan controls randomly. The odd part is the AC works fine. very strange and frustrating.

Nickthegreek

Yeah or on my e320 I remember there was a normalizaton procedure after un hooking the battery but I don't know if that is true for the w221

riisacoff

I HAVE SAME PROBLEM. RESISTOR ATTACHED TO MOTOR GETS DAMP. USUALLY BANGING FROM UNDERNEATH WILL FIX IT UNTILIT STOPS. I AM REPLACING THE DAMN RESISTOR NEXT WEEKEND.