Thread: Climate control unit circuitboard/electrical help! 1983 300SD
View Single Post
  #2  
Old 03-12-2014, 12:13 AM
SD Blue SD Blue is offline
Registered User
  
Join Date: Jun 2004
Location: West of Ft. Worth. TX
Posts: 4,186
I believe the blower speed is controlled by varying the resistance on the ground side. If you look at your diagram there is a ground (C1 pin 3) (about middle of the pushbutton control assembly). When switched to DEF, a direct ground is applied(through the PBU) to pin 8 of the Blower Speed Controller.

This forces the Blower Speed Control to HI speed.
__________________
Sam

84 300SD 350K+ miles ( Blue Belle )
Reply With Quote