If the A/C is blowing hot air all the time, it sounds like your duovalve is in need of a rebuild or replacement. Search for "duovalve" in this forum and will find lots of articles on the subject.

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"It's not about how fast you can go, but how well you can go fast."

Bob in Richmond

'97 S320 (LWB), Ruby Red Metallic, 73k miles
'97 S420V, Smoke Silver Metallic, 155k miles