I noticed today that the adjustment controls for the driver's door mirror on my 993 work correctly in the vertical, but not at all in the horizontal. Is this likely a bad motor, or wiring issue? Has anyone else had this problem?

 

Adjusting motor #965-624-901-01....Yes, I experienced the same problem. Mike

 

If both mirrors have the same issue it is the switch.

 

At my last service I, asked tech me to check mine as driver side mirror as it wouldn't move in either direction. He too the door panel off and found there was a plastic wiring connection that was not completely engaged. There is a " click lock " when the two pieces are home and it wasn't home. He pushed it together and voila. As a side benifit the battery doesn't drain nearly as quickly when the car is parked. I can now go two weeks without the battery tender. Hope your fix is as simple !

 

I have the same problem on my pass. side door. I adjusted it once by hand and just left it. No idea what the problem is., but would be interested to know what you find.

 

I was also having trouble adjusting the driver's side mirror. Found a loose connection behind door panel.

 

The problem was that the connection to the mirror switch was not fully seated. Easily corrected by removing the top door trim panel, and pushing the switch in to fully engage the pins.

I had the door apart a few weeks back, doing the door check modification, so that's when the connection got pulled out slightly.

 

The wiring harness can fracture by the A pillar inside the footwell. Only solution (apart from a new harness) is to trace and duplicate the duff wire back to the live loom. Works with pins and a voltmeter.
Total PIA