Blower won't come on sometimes
 

I have a 1981 300D 120,000miles. The AC & heater work great. Sometimes though, the blower won't come on to move the air? It gets awful hot in south Texas. Any ideas????

Have you had your blower regulator switch checked?

sometimes i cycle between ac compressor on and defrost and then 'eco' mode (with blower set to 'max' setting) to get it to work. will then usually work on all fan settings. don't know why but it does
:)

Sounds crazy, but try this: Next time the blower won't come on, twist the ignition key switch just a bit to one side then the other. I have two MB with this problem in the switch. New switches are sitting in shop waiting for chance to install. Probably best to try this with the car parked as you may turn off the engine.

I had similar problems with the blower coming on whenever it felt like it.

The switch was the problem. Make sure you have voltage at both fuse terminals of the blower motor while the car is running and the blower is on the on position but not working, that can be an indication that the blower is not getting any juice in the acc. position.

Hope that helps.

I too have also had this problem. I can confirm that it was caused by faulty ignition switch contacts. You do not need to change the whole ignition switch. You can simply replace the contact assembly at the rear of the ignition switch.
Our blower speeds are more reliable and seem to be slightly faster.