I have a question about ACC in a '97 C280....

I shouldn't complain since I'm getting nice cold air... but..... up until recently if I set the A/C temp to say, 74 degrees in AUTO, the system was able to NAIL 74 degrees and keep it there - I never had to touch it. Hot or cold outside. Now I've noticed when it gets really hot outside, the A/C will cool the cabin down just fine, but it won't let up cooling. I have to manually set the temp. to about 80-82 degrees just to keep from freezing to death. At night when it cools off outside, the A/C nails the preset temp like it should. I have to jack the temp up about 10 degrees hotter during the daytime. I took it into the shop and the tech said they had error codes for a mod valve (?) and a water pump (?). They were replaced - the A/C worked a little better, but instead of a 10 degree change now it's about a 7.

Since owning the car I've had a new compressor, expansion valve, evaporator, and a few other sundry related items replaced. With this latest "failure" the A/C is sloppy at maintaining a steady temp without me messing with it. The shop said the temp sensors were ok. I thought the sensor intake on the overhead panel might be clogged, but I was told it was ok. Any thoughts? ACC computer related maybe?

Thanks,

Mark E.
Ft. Lauderdale

__________________
Mark E.
Miami, FL
2 X 1997 C280