My blower quits blowing after driving for a while. Last fall (for $500+) the dealer replaced the electronic control (in the dash), but that was actually a shot in the dark and it didn't work. The control on the dash shows the blower should be blowing full force, yet there is no air coming out anywhere after a while. It seems to happen after I've driven it for a while on the highway at 70 mph - about thirty minutes or so. I drove it for more than an hour at less than 60 mph without a problem the other day. It seems to misbehave intermittently, but mostly after driving on the Interstate. Has anyone else experienced this problem? Could there possibly be a damper of some sort that is closing at the wrong time when it heats up? A friend suggested some kind of solenoid mis-firing? (Bear with me, please, I am of the female persuasion and not at all mechanically inclined.) When I put the car in park and then start up again, the blower will start blowing full-force. It will also start up again properly after the car has been shut off. The car is going to the dealer on April 12th to see if they can figure it out, but I found this forum online and was hoping someone here could give me some suggestions. The dealer's next "plan" is to replace the blower motor, with no guarantee that it will fix the problem. I've gotten quite frustrated especially since I live in the Midwest and now is the time to be driving with the top down and the heater on! Of course, the dealer hasn't been able to recreate the problem! I told them THIS time I'm not going to shut it off OR put it in park ... before they see that I haven't totally lost my mind! Any possible solutions from this forum? Thanks much for any possible clues ...

Possibly the evaporator is freezing-up, have you tried pressing the EC button to turn off the compressor.

Also the electronic blower regulator is a common problem on most newer Benzes if the blower quits completely(no sound).

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The blower is still making sounds like it is working, but no air coming out.

Actually I should say it WAS making sounds with no air coming out, but right now it is working. Viper300E posted back in 2003 about a similar intermittent blower motor problem (found it after I posted) and suggested jiggling the ignition key because there seemed to be "a fine line in the ignition switch that allows the play over time to cut out the electrical power to the blower motor."

I "jiggled" the key on Saturday, and can't get it to misbehave again! I'm still taking it in to the dealer on Tuesday morning and having them check out the ignition because I don't want more problems further down the road.

Miracle of miracles ... I hope this is the answer. I actually had to turn DOWN the blower this afternoon!

Thanks for the suggestions! I'm copying the threads and bringing them in to the dealer with me tomorrow just in case the ignition isn't causing the problem. I sure would have thought the dealer would have searched for an answer the last few times I was there with the intermittent problem - rather than just throwing in new parts and crossing their fingers. All it took was a little Internet search to find this forum on my part ...

Oh, well, live and learn ... and pay ... and pay ... and pay ...

I worked ona 140 that needed an ignition switch to fix a non-operating blower motor. Wasn't powering up the regulator. And yes "jiggling" the switch would temporarily fix it. BUT if this were the case you wouldn't hear the blower motor running, it'd be dead.
On a 140, they can bust clips that hold the fresh air door open. I don't think the 129 is like this. BUT if it is, this is how you determine if this is the problem on the 140: Press the "recirc" button when you are experiencing this "No air flow" problem. You are then providing the climate control with an intake air source (the interior of the car). Otherwise if the outside air flap is shut and the car isn't in recirc mode, the car has NO intake source at all. Try it.
I wouldn't pursue a blower motor problem at all if the fan is always running, unless you think the motor is running and the fan isn't turning (???)

Gilly

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Same problem with my 99 SL 500
Took it to an indie A/C shop.the blower will work some times and then it would not come on at all other times,the mech. dug it out of the car, this thing is buried in between the engine firewall and the back of the dash below the filter assy under the hood.I have all the parts that were replaced and it clearly shows that the double squirrel cage plastic blower housing MB pn.A 129 830 01 03 .cracked around the (plastic) retaining clips allowing the squirrel cage to rub against the housing,evidently slowing or stopping the blower from turning depending on the selected fan speed.never heard any scrapping noise that will point this out so I was lost trying to diagnose it.This is not an electrical motor is an electromagnetic contraption that looks like the cooling fins on a motorcycle engine, this is activated by a control module another cooling fin looking contraption,BEHR 129 821 33 51,that burned up trying to keep the blower turning, This was $900.00 parts and labor with original equipment replacement and after examining this cheaply made parts that I will expect to find in a Hunday it a big possibility that you are having the same problems.GOOD LUCK