There is a guy who rebuilds 4 and 5 button thermostats on eBay. Very reasonable and mine has worked for over 4 years with no issues.
Tom and all with 4 Button Tstats or '99 Marquis,
I was all ready to send my 4 button to this guy on Ebay, but figured it clean the contacts first because another online poster recommended it could be done.
I removed the unit by unscrewing from the wall and disconnecting the cable, opened it up, and used a QTip with alcohol on the locations where the switch contacts were under each button. I felt as I was doing this that, "there is no way this is going to work". I even got part numbers of the contact switches, or attempted to, so that I could see what new ones cost - no luck there.
So I wondered how this Ebay guy was "fixing" these things. After returning the unit to the coach, and feeling like I'd done nothing, the unit worked like a champ. My only guess is that over the years we keep pushing those buttons with dirty fingers and eventually create the problem, which is cleaned up with simple Qtip and alcohol, so I would suggest rather than sending your unit to the ebay guy along with $100 I think it is, that you try cleaning it, then try keeping your hands clean while using it. Mine's working fine now even after a year since I did the cleaning...not perfect but it was awful before the cleaning in that I couldn't get anything to happen using the buttons to turn the temp up or down. Now, sometimes, I might bounce a couple degrees, but its responsive.
Anyway, just my experience. I can not imagine that this guy for $100 can refurb these units, but I bet he has a better cleaning operation than I used, and that's all he does.
So far, Tom, my '99 is cooling well both units, at least according to my wife. We only run it to about 73 or 74 degrees, so for now all is well. This coach of mine I am happy to say just doesn't seem to have been pushed that hard in the 65,000 miles or so before I purchased it, and has spend most of its life (until I purchased it 9/4/13) inside. Now I store it under cover but it isn't inside any longer, so I guess its beginning to wear a bit more.
I'll close by knocking on wood.
Mike