Change-over Switch Not Being Activated - Heating/Cooling Blower Selection

[1simpson@bellsouth.net]

Hello all, there has been a lot posted about the infamous 2-blower climate control and the change-over switch system on the W114/W115, in my case a 1976 240D. My cooling blower has worked all summer, but the heater blower does not come as it should. Today I manually flipped the lever on the change-over switch and the heater blower works, which also means the change-over switch is good. However whatever operates the linkage to the change-over switch is not doing its job.

Does anyone have any advice on troubleshooting this? I believe its a vacuum system and when I push the linkage at the switch, it sounds like something is happening inside the center console where the A/C knob, radio, etc are located. Would appreciate very much any tips on this.

[Sugar Bear]

The switch in the top center has both electric and vacuum actions. It should close a vacuum door which pushes/pulls the rod to open/close the switch.

The lower switch alongside the radio has a capillary tube which senses evaporator temp to then turn the compressor on/off.

Probably easiest to see if the other end of the control rod on the changeover switch became disconnected. Next would be confirm vacuum to and then in/out of the fan speed switch in the top center.

Good luck!!!