Blower motor working then not working
 

Got in my 1990 300CE yesterday and was driving around town with A/C on. Stopped and started several times with A/C on and then the last time went to turn on the A/C and no blower motor...does not seem to respond at any level with any of the fan speeds on low, high, or auto functions.

No A/C or E/C or function of any of the climate controls. Fuses are good, removed and reinstalled.

Could this be a blower regulator or blower itself...how would I test this scenario?

Blower
 

Check the blower motor strip fuse located in a plastic coffin like box off the left front shock tower. It may be bad even though it looks intact.

If strip fuse is OK there could be a number of other causes such as you mentioned or even a bad climate control panel.

after you start the car...try backing off the key a millimeter.... strip fuse second... if that doesn't work.... probably the regulator... about a 45 minute fix

Would you change the blower motor at the same time as the regulator?

I think its a good idea. A blower motor is only $90 or so. transfer the squirrel cages to the new one.. be sure to blow out the box and whatever you can on the evaporator.

if you pull the blower motor...hook it up to jumper cables and the battery... and hold on.. if it spins like it will jump out of your hands...it's ok... i have owned a lot of 124s... and it's always the regulator... i keep a spare one in my parts bin......

Weird, went to get in the car to go someplace yesterday and turned the key with all buttons on the climate control "out" including the "O" and had the key in the #2 position before starting the car....blower fan came on...tried to put on the "EC" and "A/C" but the blower turned off.

Could this be a symptom of bad climate control rather than bad blower regulator?

It's possible. The pbus will wear out. You can swap out a known good unit, or isolate the individual components to rule out their function as a cause.

TO THE PULLAPART!

Climate Control Unit
 

Could be. These units behave erratically with age. My last CCU was under $20 at Pick & Pull. Easy to replace too.