Hi,

This is for a 1980 300SD, 116 body style.

One day the blower quit working. It works if you set it on defrost. But will not work in any other setting. I replaced the blower motor a little over a year ago and since it works in defrost, I doubt if it is the motor.

So what should my next step be? Is this a problem with the controls on the dash or is this a vacuum problem?

If this is a vacuum problem, I have heard you can buy the whole climate control vacuum system as a harness. Is this a recommended way to go? Or do I just start tracking through the system for leaks?

i had the same problem with my 300d...78, same climate control(kinda) it simply stoped! now it works fine, odly enough it stoped after i replaced thermostat to get engine up to operating temp...hummm anyway is this in heat or ac mode?


keep us posted

This happens in both the A/C and the heating mode.

But the blower works in the defrost setting.

if the blower comes on in defrost mode only it could be the vacuum actuator at the blower motor assy.to access you will need to remove the under dash panel cover on the passenger side.you will then see the blower assy and vacuum actuator.watch this as you press the auto low button on the dash.you should see the actuator move.if it does not the chances are it needs replacement.you can replace the rubber end pieces.search on this sight.i beleive there is a source for these parts