Hello Fellow Blazer Fans,

Has anyone ever been able to successfully clean and/or rehabilitate the rubber diaphragm in the HVAC rotary vacuum switch in the climate control panel? I'm wondering if there's a way to avoid buying a whole new panel just for that one diaphragm.

Here's the back story, for those interested:

When I bought my '98 Jimmy last year the climate control panel had a vacuum leak. The seller included a replacement panel from a junk yard. I installed it and it worked fine for a few weeks after which time it started leaking vacuum—and ATF.

I went through the usual diagnostic procedure and found the transfer case overfilled. I pulled the transfer case and replaced the input shaft seal. I replaced the 4WD actuator under the battery. I cleaned out every single vacuum line with Simple Green and compressed air, including every vacuum line from every actuator back to the control panel. I replaced the 4WD switch on the transfer case. I bought a brand-new control panel from the dealer and installed it. Everything worked fine from January until a couple weeks ago.

I pulled the control panel again and, once again, it was dripping ATF. I took the back off the rotary vacuum switch. It, and the rubber diaphragm that rotates inside the switch, were covered in ATF. I cleaned both the back of the switch and the diaphragm with Simple Green and wiped them absolutely dry and then let them sit out and dry some more. I reassembled the switch and installed it to test it out and it was still leaking vacuum. I also rechecked the vacuum actuators and they test out OK. When I bypass the rotary vacuum switch and apply engine vacuum to the actuators directly they operate and route the air normally.

I'd like to try and rehabilitate the rubber diaphragm if possible and not buy yet another control panel. It won't sit in the metal disc underneath it properly; the tabs on the rubber diaphragm cause it to bow upward when inserted in the disc.

Also, in case you're curious, I haven't gotten under the truck to see if there's ATF in the vacuum lines coming off the transfer case. I'll check that next and see what's up there. I want to complete the dash portion of the repair while everything is disassembled before I check the transfer case and vacuum lines for excess fluid.