I've been repairing the climate control on my '82 300TDT and I found that the only vacuum element that had failed was the dual-acting defroster element. The only places I could find it, it was listed as "Special Order, Limited Availability". It also cost about $100. With a desire to get the car back on the road sooner than later I took a gamble and ordered the MUCH more readily available and significantly less expensive ($40) dual acting element from a W124, part #1248001175. It looked remarkably similar. I figured I might have to bend or swap the arm and possibly rig the mounting. It turned out to be even easier than I thought. Apparently the guys at Behr like playing with legos. Yes, the arms are different, and yes, the mounting is different, but it all clips together just ducky. I had to drill out the rivet on that held the old arm in place.


After that, I un-clipped the arm from the new part. It comes with a nifty little clip and the hole size and offset are perfect for the w123 arm. I un-clipped the base and un-clipped the top part (the nipple comes out the side on the new one and is in the center of the old one. It all clipped back together again perfectly. Maybe 10 minutes, start to finish. Here it is all reassembled.

And here it is reinstalled.


BTW, if anyone needs to install just that element, it is fairly easily accomplished by removing the lower panel and instrument cluster and detaching the left vent tube and moving it out of the way. No dash removal necessary. If vacuum lines from vacuum solenoid valves 1 and 3 leak, then it is very likely that element that is bad (both go to that element).