I have a 1995 S500.

Will the cheap Radio Shack code reader work with this car? Or does it require a full digital reader?
To shortcut some details about code readers, here is my problem.

I started receiving a CHECK ENGINE light last year. The car ran perfectly, except for one day when it had a bad miss for about twenty minutes. It then went away. At a service, I had the dealer check it and they told me I had a bad wiring harness to the engine control computer and also corroded distributor caps and rotors. They said it was a $2100 fix. I told them to shove it. I cleaned my rotors and caps (they were funky apparently from water intrusion during an overzealous detail or something). The car continued to run well and the weird miss never recurred. The CHECK ENGINE light just became "normal" as far as I was concerned. Also during this time, I had to run the car thru emissions testing for new plates and it was squeaky clean as always.

Last week, I stopped at a neighbor's house and spoke with him in the driveway (me in the car, him standing outside). His toddler child was acting up and needed attention so I tossed her my keys to play with. She proceeded to lock and unlock the doors thirty of forty times. When I went to leave, I retrieved the keys through my open window and went to start the car. Since the doors were locked (from outside) the alarm went off. I pulled the keys out and shut off the alarm, started the car, and drove away.

As I drove away, I noticed my dash vents blowing hot air. Also the defroster was blowing hot air. Not just uncooled, air, but hot air. The AC display was reading normally and showed 70 degrees on both sides. I went to change the temp and nothing responded (the display had normal lights and readings in the LCDs but nothing would respond). I went to change the blower speed and nothing responded. I went to pushing buttons and nothing responded. I rolled the windows down so I wouldn't melt.

About this time (it was dusk) I turned on the headlamps. The AC display went blank except for the EC light. I turned the lights off, the display came back on but remained unresponsive. I pulled over and shut off the car. I restarted with no change (same frozen display). When I got home I disconnected the battery and left it off for four days.

When I reconnected the battery, the car started normally (a bit rough at first), the AC display was normal, and the air worked normally. The CHECK ENGINE light was out, and the day went well. The next morning, I started the car and the air went on full hot and the display was frozen and the CHECK ENGINE light was on.

The car is currently sitting with the battery disconnected again and I plan to retry tomorrow.

Any ideas?
Can I use the cheapo code reader on this car or is it a digital system that is not compatible with the cheapo reader? Can I use the LED and pushbutton on the N59 box? What do those codes mean?

Any ideas about the possessed AC?

I'm a newbie and hope I have presented my inquiry properly..

mc