1996 S500 (w140) bad AC control unit
 

On my S500 the EC light on the control unit won't go off. I have done the following.

1. REmoved all the buttons and inserts to insure the indent to the system actually depresses. It does.

2. I also have a 98 E420, so I swapped the control units and when I do this, the 98 control unit runs the AC fine in the 96(EC light off), and the light on the 96 unit stays on when I put it into the 98.

So, I guess I need a new control unit. Is it less expensive to get the broken one fixed somewhere or buy a rebuilt from allparts. That said, I see that I they are coded somehow and you have to buy the correct one. What do I tell Philip I need?

KG