Restoring 69 Charger a/c system. Replaced inop vacuum switch with NOS 3502126B which was advertised as supersede for 68-70B/C bodies. Switch seems to work ok except it energizes the a/c clutch on defrost mode. 69 Serv Manual says no a/c clutch on defrost. Anyone know whats going on here?

I'm wondering if the A/C clutch gets engaged on defrost on 68-70 B/C bodies. If "no" that would make me think there is a problem elsewhere. Here's a BTT for ya.

According to the 69 serv manual, compressor (a/c clutch) is off during defrost. Read somewhere that later switch supersedes may energize clutch for defrost. Don't know how the part numbers (there are several) map to this...

If having the AC on for defrost bothers you, then push the button in and pull it back out to deenergize the AC.

It's a good thing to have it engage, just like a modern car does it. Removes moisture when the compressor runs.