AC went out when igniton was replaced

I took my 99 Town and Country in to have the ignition replaced (for the 2nd time). The tow truck driver pulled the transmission cable (?) so that he could tow it. When I got it back the AC blew hot. The dealer thought that the AC was not grounded. Now they say that I need to replace a wire in the engine compartment wiring harness for $450. Was the AC problem caused by the work they did on the ignition?