My wife drives our '87 300d the most.The other day she said it was blowing COLD air even with the temp selector on full hot.
A week later she said it was doing it again.Sure enough...the a/c compressor was running with the EC button on,temp set to hot and fan on low.I unplugged both pressure switches by the the condensor.I got the compressor to disengage but another odd thing arose.The fan quits blowing when the "O"(off) button is pressed but when you take your finger off the button it will start blowing.Push in on the button...fan goes off...let go...comes on ect,ect.Should I be looking into a new control panel? How much$$$?

Actually there is one on Ebay right now; it's at $25 right now. http://cgi.ebay.com/ebaymotors/aw-cgi/eBayISAPI.dll?ViewItem&item=597011312&r=0&t=0&showTutorial=0&ed=1004244391&indexURL=0&rd=1
I have no relationship to the seller, and Ebay warns you to beware. However, I've bought a couple of <$50 items for my car on Ebay and have been lucky so far.

__________________
Bob Roe
Lehigh Valley PA USA
1973 Olds 88, 1972 MB 280SE, 1978 Datsun 280Z, 1971 Ford T-Bird, 1972 Olds 88, 1983 Nissan Sentra, 1985 Sentra, 1973 230.6, 1990 Acura Integra, 1991 Volvo 940GLE wagon, 1983 300SD, 1984 300SD, 1995 Subaru Legacy L wagon, 2002 Mountaineer, 1991 300TE wagon, 2008 Murano, 2007 R320CDI 4Matic 52K, some Hyundai, 2008 BMW 535xi wagon, all gone... currently
2007 Honda Odyssey Touring, 2014 E350 4matic

Larry sent me a great diagnostic bulletin on climate contol which may help.

Shoot me your fax number and I'll send it to you Monday AM

JCD